diff --git a/src/app/classes/delegate.ts b/src/app/classes/delegate.ts
index a3c9665fa..48a86308c 100644
--- a/src/app/classes/delegate.ts
+++ b/src/app/classes/delegate.ts
@@ -40,18 +40,18 @@ export class CoreDelegate {
     /**
      * Default handler
      */
-    protected defaultHandler: CoreDelegateHandler;
+    protected defaultHandler?: CoreDelegateHandler;
 
     /**
      * Time when last updateHandler functions started.
      */
-    protected lastUpdateHandlersStart: number;
+    protected lastUpdateHandlersStart = 0;
 
     /**
      * Feature prefix to check is feature is enabled or disabled in site.
      * This check is only made if not false. Override on the subclass or override isFeatureDisabled function.
      */
-    protected featurePrefix: string;
+    protected featurePrefix?: string;
 
     /**
      * Name of the property to be used to index the handlers. By default, the handler's name will be used.
@@ -78,7 +78,7 @@ export class CoreDelegate {
     /**
      * Function to resolve the handlers init promise.
      */
-    protected handlersInitResolve: () => void;
+    protected handlersInitResolve!: () => void;
 
     /**
      * Constructor of the Delegate.
@@ -110,7 +110,7 @@ export class CoreDelegate {
      * @param params Parameters to pass to the function.
      * @return Function returned value or default value.
      */
-    protected executeFunctionOnEnabled<T = unknown>(handlerName: string, fnName: string, params?: unknown[]): T {
+    protected executeFunctionOnEnabled<T = unknown>(handlerName: string, fnName: string, params?: unknown[]): T | undefined {
         return this.execute<T>(this.enabledHandlers[handlerName], fnName, params);
     }
 
@@ -123,7 +123,7 @@ export class CoreDelegate {
      * @param params Parameters to pass to the function.
      * @return Function returned value or default value.
      */
-    protected executeFunction<T = unknown>(handlerName: string, fnName: string, params?: unknown[]): T {
+    protected executeFunction<T = unknown>(handlerName: string, fnName: string, params?: unknown[]): T | undefined {
         return this.execute(this.handlers[handlerName], fnName, params);
     }
 
@@ -136,7 +136,7 @@ export class CoreDelegate {
      * @param params Parameters to pass to the function.
      * @return Function returned value or default value.
      */
-    private execute<T = unknown>(handler: CoreDelegateHandler, fnName: string, params?: unknown[]): T {
+    private execute<T = unknown>(handler: CoreDelegateHandler, fnName: string, params?: unknown[]): T | undefined {
         if (handler && handler[fnName]) {
             return handler[fnName].apply(handler, params);
         } else if (this.defaultHandler && this.defaultHandler[fnName]) {
@@ -252,7 +252,7 @@ export class CoreDelegate {
             this.updatePromises[siteId] = {};
         }
 
-        if (!CoreSites.instance.isLoggedIn() || this.isFeatureDisabled(handler, currentSite)) {
+        if (!CoreSites.instance.isLoggedIn() || this.isFeatureDisabled(handler, currentSite!)) {
             promise = Promise.resolve(false);
         } else {
             promise = Promise.resolve(handler.isEnabled()).catch(() => false);
@@ -270,6 +270,8 @@ export class CoreDelegate {
                     delete this.enabledHandlers[key];
                 }
             }
+
+            return;
         }).finally(() => {
             // Update finished, delete the promise.
             delete this.updatePromises[siteId][handler.name];
@@ -295,7 +297,7 @@ export class CoreDelegate {
      * @return Resolved when done.
      */
     protected async updateHandlers(): Promise<void> {
-        const promises = [];
+        const promises: Promise<void>[] = [];
         const now = Date.now();
 
         this.logger.debug('Updating handlers for current site.');
diff --git a/src/app/classes/errors/ajaxwserror.ts b/src/app/classes/errors/ajaxwserror.ts
index c2e5df5c3..338a0706a 100644
--- a/src/app/classes/errors/ajaxwserror.ts
+++ b/src/app/classes/errors/ajaxwserror.ts
@@ -28,7 +28,7 @@ export class CoreAjaxWSError extends CoreError {
     backtrace?: string; // Backtrace. Only if debug mode is enabled.
     available?: number; // Whether the AJAX call is available. 0 if unknown, 1 if available, -1 if not available.
 
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     constructor(error: any, available?: number) {
         super(error.message);
 
diff --git a/src/app/classes/errors/wserror.ts b/src/app/classes/errors/wserror.ts
index 27e3df43f..a3b4c9c0f 100644
--- a/src/app/classes/errors/wserror.ts
+++ b/src/app/classes/errors/wserror.ts
@@ -27,6 +27,7 @@ export class CoreWSError extends CoreError {
     debuginfo?: string; // Debug info. Only if debug mode is enabled.
     backtrace?: string; // Backtrace. Only if debug mode is enabled.
 
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     constructor(error: any) {
         super(error.message);
 
diff --git a/src/app/classes/interceptor.ts b/src/app/classes/interceptor.ts
index c7fcaa782..34c8e4f4d 100644
--- a/src/app/classes/interceptor.ts
+++ b/src/app/classes/interceptor.ts
@@ -30,7 +30,7 @@ export class CoreInterceptor implements HttpInterceptor {
      * @param addNull Add null values to the serialized as empty parameters.
      * @return Serialization of the object.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     static serialize(obj: any, addNull?: boolean): string {
         let query = '';
 
@@ -61,7 +61,7 @@ export class CoreInterceptor implements HttpInterceptor {
         return query.length ? query.substr(0, query.length - 1) : query;
     }
 
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     intercept(req: HttpRequest<any>, next: HttpHandler): Observable<any> {
         // Add the header and serialize the body if needed.
         const newReq = req.clone({
diff --git a/src/app/classes/ion-loading.ts b/src/app/classes/ion-loading.ts
index 370b9fa25..450e0aced 100644
--- a/src/app/classes/ion-loading.ts
+++ b/src/app/classes/ion-loading.ts
@@ -25,7 +25,7 @@ export class CoreIonLoadingElement {
 
     constructor(public loading: HTMLIonLoadingElement) { }
 
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     async dismiss(data?: any, role?: string): Promise<boolean> {
         if (!this.isPresented || this.isDismissed) {
             this.isDismissed = true;
diff --git a/src/app/classes/queue-runner.ts b/src/app/classes/queue-runner.ts
index 3b05b1369..fb70f70b9 100644
--- a/src/app/classes/queue-runner.ts
+++ b/src/app/classes/queue-runner.ts
@@ -91,7 +91,7 @@ export class CoreQueueRunner {
             return;
         }
 
-        const item = this.orderedQueue.shift();
+        const item = this.orderedQueue.shift()!;
         this.numberRunning++;
 
         try {
diff --git a/src/app/classes/site.ts b/src/app/classes/site.ts
index c02a3259f..7ff9b058d 100644
--- a/src/app/classes/site.ts
+++ b/src/app/classes/site.ts
@@ -32,12 +32,15 @@ import { CoreError } from '@classes/errors/error';
 import { CoreWSError } from '@classes/errors/wserror';
 import { CoreLogger } from '@singletons/logger';
 import { Translate } from '@singletons/core.singletons';
+import { CoreIonLoadingElement } from './ion-loading';
 
 /**
  * Class that represents a site (combination of site + user).
  * It will have all the site data and provide utility functions regarding a site.
  * To add tables to the site's database, please use CoreSitesProvider.registerSiteSchema. This will make sure that
  * the tables are created in all the sites, not just the current one.
+ *
+ * @todo: Refactor this class to improve "temporary" sites support (not fully authenticated).
  */
 export class CoreSite {
 
@@ -78,17 +81,17 @@ export class CoreSite {
 
     // Rest of variables.
     protected logger: CoreLogger;
-    protected db: SQLiteDB;
+    protected db?: SQLiteDB;
     protected cleanUnicode = false;
     protected lastAutoLogin = 0;
     protected offlineDisabled = false;
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected ongoingRequests: { [cacheId: string]: Promise<any> } = {};
     protected requestQueue: RequestQueueItem[] = [];
-    protected requestQueueTimeout: number = null;
-    protected tokenPluginFileWorks: boolean;
-    protected tokenPluginFileWorksPromise: Promise<boolean>;
-    protected oauthId: number;
+    protected requestQueueTimeout: number | null = null;
+    protected tokenPluginFileWorks?: boolean;
+    protected tokenPluginFileWorksPromise?: Promise<boolean>;
+    protected oauthId?: number;
 
     /**
      * Create a site.
@@ -101,9 +104,16 @@ export class CoreSite {
      * @param config Site public config.
      * @param loggedOut Whether user is logged out.
      */
-    constructor(public id: string, public siteUrl: string, public token?: string, public infos?: CoreSiteInfo,
-            public privateToken?: string, public config?: CoreSiteConfig, public loggedOut?: boolean) {
-        this.logger = CoreLogger.getInstance('CoreWSProvider');
+    constructor(
+        public id: string | undefined,
+        public siteUrl: string,
+        public token?: string,
+        public infos?: CoreSiteInfo,
+        public privateToken?: string,
+        public config?: CoreSiteConfig,
+        public loggedOut?: boolean,
+    ) {
+        this.logger = CoreLogger.getInstance('CoreSite');
         this.setInfo(infos);
         this.calculateOfflineDisabled();
 
@@ -125,6 +135,11 @@ export class CoreSite {
      * @return Site ID.
      */
     getId(): string {
+        if (!this.id) {
+            // Shouldn't happen for authenticated sites.
+            throw new CoreError('This site doesn\'t have an ID');
+        }
+
         return this.id;
     }
 
@@ -143,6 +158,11 @@ export class CoreSite {
      * @return Site token.
      */
     getToken(): string {
+        if (!this.token) {
+            // Shouldn't happen for authenticated sites.
+            throw new CoreError('This site doesn\'t have a token');
+        }
+
         return this.token;
     }
 
@@ -151,7 +171,7 @@ export class CoreSite {
      *
      * @return Site info.
      */
-    getInfo(): CoreSiteInfo {
+    getInfo(): CoreSiteInfo | undefined {
         return this.infos;
     }
 
@@ -160,7 +180,7 @@ export class CoreSite {
      *
      * @return Site private token.
      */
-    getPrivateToken(): string {
+    getPrivateToken(): string | undefined {
         return this.privateToken;
     }
 
@@ -170,6 +190,11 @@ export class CoreSite {
      * @return Site DB.
      */
     getDb(): SQLiteDB {
+        if (!this.db) {
+            // Shouldn't happen for authenticated sites.
+            throw new CoreError('Site DB doesn\'t exist');
+        }
+
         return this.db;
     }
 
@@ -179,9 +204,12 @@ export class CoreSite {
      * @return User's ID.
      */
     getUserId(): number {
-        if (typeof this.infos != 'undefined' && typeof this.infos.userid != 'undefined') {
-            return this.infos.userid;
+        if (!this.infos) {
+            // Shouldn't happen for authenticated sites.
+            throw new CoreError('Site info could not be fetched.');
         }
+
+        return this.infos.userid;
     }
 
     /**
@@ -190,7 +218,7 @@ export class CoreSite {
      * @return Site Home ID.
      */
     getSiteHomeId(): number {
-        return this.infos && this.infos.siteid || 1;
+        return this.infos?.siteid || 1;
     }
 
     /**
@@ -203,7 +231,7 @@ export class CoreSite {
             // Overridden by config.
             return CoreConfigConstants.sitename;
         } else {
-            return this.infos && this.infos.sitename || '';
+            return this.infos?.sitename || '';
         }
     }
 
@@ -249,7 +277,7 @@ export class CoreSite {
      *
      * @return OAuth ID.
      */
-    getOAuthId(): number {
+    getOAuthId(): number | undefined {
         return this.oauthId;
     }
 
@@ -258,14 +286,14 @@ export class CoreSite {
      *
      * @param New info.
      */
-    setInfo(infos: CoreSiteInfo): void {
+    setInfo(infos?: CoreSiteInfo): void {
         this.infos = infos;
 
         // Index function by name to speed up wsAvailable method.
-        if (infos && infos.functions) {
+        if (infos?.functions) {
             infos.functionsByName = {};
             infos.functions.forEach((func) => {
-                infos.functionsByName[func.name] = func;
+                infos.functionsByName![func.name] = func;
             });
         }
     }
@@ -298,7 +326,7 @@ export class CoreSite {
      *
      * @param oauth OAuth ID.
      */
-    setOAuthId(oauthId: number): void {
+    setOAuthId(oauthId: number | undefined): void {
         this.oauthId = oauthId;
     }
 
@@ -317,9 +345,9 @@ export class CoreSite {
      * @return Whether can access my files.
      */
     canAccessMyFiles(): boolean {
-        const infos = this.getInfo();
+        const info = this.getInfo();
 
-        return infos && (typeof infos.usercanmanageownfiles === 'undefined' || infos.usercanmanageownfiles);
+        return !!(info && (typeof info.usercanmanageownfiles === 'undefined' || info.usercanmanageownfiles));
     }
 
     /**
@@ -328,9 +356,9 @@ export class CoreSite {
      * @return Whether can download files.
      */
     canDownloadFiles(): boolean {
-        const infos = this.getInfo();
+        const info = this.getInfo();
 
-        return infos && infos.downloadfiles > 0;
+        return !!info?.downloadfiles && info?.downloadfiles > 0;
     }
 
     /**
@@ -340,22 +368,20 @@ export class CoreSite {
      * @param whenUndefined The value to return when the parameter is undefined.
      * @return Whether can use advanced feature.
      */
-    canUseAdvancedFeature(feature: string, whenUndefined: boolean = true): boolean {
-        const infos = this.getInfo();
-        let canUse = true;
+    canUseAdvancedFeature(featureName: string, whenUndefined: boolean = true): boolean {
+        const info = this.getInfo();
 
-        if (typeof infos.advancedfeatures === 'undefined') {
-            canUse = whenUndefined;
-        } else {
-            for (const i in infos.advancedfeatures) {
-                const item = infos.advancedfeatures[i];
-                if (item.name === feature && item.value === 0) {
-                    canUse = false;
-                }
-            }
+        if (typeof info?.advancedfeatures === 'undefined') {
+            return whenUndefined;
         }
 
-        return canUse;
+        const feature = info.advancedfeatures.find((item) => item.name === featureName);
+
+        if (!feature) {
+            return whenUndefined;
+        }
+
+        return feature.value !== 0;
     }
 
     /**
@@ -364,9 +390,9 @@ export class CoreSite {
      * @return Whether can upload files.
      */
     canUploadFiles(): boolean {
-        const infos = this.getInfo();
+        const info = this.getInfo();
 
-        return infos && infos.uploadfiles > 0;
+        return !!info?.uploadfiles && info?.uploadfiles > 0;
     }
 
     /**
@@ -396,7 +422,7 @@ export class CoreSite {
      * @param preSets Extra options.
      * @return Promise resolved with the response, rejected with CoreWSError if it fails.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     read<T = unknown>(method: string, data: any, preSets?: CoreSiteWSPreSets): Promise<T> {
         preSets = preSets || {};
         if (typeof preSets.getFromCache == 'undefined') {
@@ -420,7 +446,7 @@ export class CoreSite {
      * @param preSets Extra options.
      * @return Promise resolved with the response, rejected with CoreWSError if it fails.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     write<T = unknown>(method: string, data: any, preSets?: CoreSiteWSPreSets): Promise<T> {
         preSets = preSets || {};
         if (typeof preSets.getFromCache == 'undefined') {
@@ -455,13 +481,13 @@ export class CoreSite {
      * This method is smart which means that it will try to map the method to a compatibility one if need be, usually this
      * means that it will fallback on the 'local_mobile_' prefixed function if it is available and the non-prefixed is not.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-    request<T = unknown>(method: string, data: any, preSets: CoreSiteWSPreSets, retrying?: boolean): Promise<T> {
-        const initialToken = this.token;
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    async request<T = unknown>(method: string, data: any, preSets: CoreSiteWSPreSets, retrying?: boolean): Promise<T> {
+        const initialToken = this.token || '';
         data = data || {};
 
         if (!CoreApp.instance.isOnline() && this.offlineDisabled) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.errorofflinedisabled')));
+            throw new CoreError(Translate.instance.instant('core.errorofflinedisabled'));
         }
 
         // Check if the method is available, use a prefixed version if possible.
@@ -474,12 +500,12 @@ export class CoreSite {
             } else {
                 this.logger.error(`WS function '${method}' is not available, even in compatibility mode.`);
 
-                return Promise.reject(new CoreError(Translate.instance.instant('core.wsfunctionnotavailable')));
+                throw new CoreError(Translate.instance.instant('core.wsfunctionnotavailable'));
             }
         }
 
         const wsPreSets: CoreWSPreSets = {
-            wsToken: this.token,
+            wsToken: this.token || '',
             siteUrl: this.siteUrl,
             cleanUnicode: this.cleanUnicode,
             typeExpected: preSets.typeExpected,
@@ -509,24 +535,25 @@ export class CoreSite {
         data = CoreWS.instance.convertValuesToString(data, wsPreSets.cleanUnicode);
         if (data == null) {
             // Empty cleaned text found.
-            return Promise.reject(new CoreError(Translate.instance.instant('core.unicodenotsupportedcleanerror')));
+            throw new CoreError(Translate.instance.instant('core.unicodenotsupportedcleanerror'));
         }
 
         const cacheId = this.getCacheId(method, data);
 
         // Check for an ongoing identical request if we're not ignoring cache.
         if (preSets.getFromCache && this.ongoingRequests[cacheId]) {
-            return this.ongoingRequests[cacheId].then((response) =>
-                // Clone the data, this may prevent errors if in the callback the object is modified.
-                CoreUtils.instance.clone(response),
-            );
+            const response = await this.ongoingRequests[cacheId];
+
+            // Clone the data, this may prevent errors if in the callback the object is modified.
+            return CoreUtils.instance.clone(response);
         }
 
         const promise = this.getFromCache<T>(method, data, preSets, false).catch(() => {
             if (preSets.forceOffline) {
                 // Don't call the WS, just fail.
-                return Promise.reject(new CoreError(Translate.instance.instant('core.cannotconnect',
-                    { $a: CoreSite.MINIMUM_MOODLE_VERSION })));
+                throw new CoreError(
+                    Translate.instance.instant('core.cannotconnect', { $a: CoreSite.MINIMUM_MOODLE_VERSION }),
+                );
             }
 
             // Call the WS.
@@ -558,7 +585,7 @@ export class CoreSite {
                     CoreEvents.instance.trigger(CoreEventsProvider.USER_DELETED, { params: data }, this.id);
                     error.message = Translate.instance.instant('core.userdeleted');
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 } else if (error.errorcode === 'forcepasswordchangenotice') {
                     // Password Change Forced, trigger event. Try to get data from cache, the event will handle the error.
                     CoreEvents.instance.trigger(CoreEventsProvider.PASSWORD_CHANGE_FORCED, {}, this.id);
@@ -572,7 +599,7 @@ export class CoreSite {
                     CoreEvents.instance.trigger(CoreEventsProvider.SITE_POLICY_NOT_AGREED, {}, this.id);
                     error.message = Translate.instance.instant('core.login.sitepolicynotagreederror');
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 } else if (error.errorcode === 'dmlwriteexception' && CoreTextUtils.instance.hasUnicodeData(data)) {
                     if (!this.cleanUnicode) {
                         // Try again cleaning unicode.
@@ -583,7 +610,7 @@ export class CoreSite {
                     // This should not happen.
                     error.message = Translate.instance.instant('core.unicodenotsupported');
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 } else if (error.exception === 'required_capability_exception' || error.errorcode === 'nopermission' ||
                         error.errorcode === 'notingroup') {
                     // Translate error messages with missing strings.
@@ -596,16 +623,16 @@ export class CoreSite {
                     // Save the error instead of deleting the cache entry so the same content is displayed in offline.
                     this.saveToCache(method, data, error, preSets);
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 } else if (preSets.cacheErrors && preSets.cacheErrors.indexOf(error.errorcode) != -1) {
                     // Save the error instead of deleting the cache entry so the same content is displayed in offline.
                     this.saveToCache(method, data, error, preSets);
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 } else if (typeof preSets.emergencyCache !== 'undefined' && !preSets.emergencyCache) {
                     this.logger.debug(`WS call '${method}' failed. Emergency cache is forbidden, rejecting.`);
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 }
 
                 if (preSets.deleteCacheIfWSError && CoreUtils.instance.isWebServiceError(error)) {
@@ -614,7 +641,7 @@ export class CoreSite {
                         // Ignore errors.
                     });
 
-                    return Promise.reject(new CoreWSError(error));
+                    throw new CoreWSError(error);
                 }
 
                 this.logger.debug(`WS call '${method}' failed. Trying to use the emergency cache.`);
@@ -623,11 +650,11 @@ export class CoreSite {
 
                 return this.getFromCache<T>(method, data, preSets, true).catch(() => Promise.reject(new CoreWSError(error)));
             });
-        // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
         }).then((response: any) => {
             // Check if the response is an error, this happens if the error was stored in the cache.
             if (response && (typeof response.exception != 'undefined' || typeof response.errorcode != 'undefined')) {
-                return Promise.reject(new CoreWSError(response));
+                throw new CoreWSError(response);
             }
 
             return response;
@@ -636,15 +663,17 @@ export class CoreSite {
         this.ongoingRequests[cacheId] = promise;
 
         // Clear ongoing request after setting the promise (just in case it's already resolved).
-        return promise.finally(() => {
+        try {
+            const response = await promise;
+
+            // We pass back a clone of the original object, this may prevent errors if in the callback the object is modified.
+            return CoreUtils.instance.clone(response);
+        } finally {
             // Make sure we don't clear the promise of a newer request that ignores the cache.
             if (this.ongoingRequests[cacheId] === promise) {
                 delete this.ongoingRequests[cacheId];
             }
-        }).then((response) =>
-            // We pass back a clone of the original object, this may prevent errors if in the callback the object is modified.
-            CoreUtils.instance.clone(response),
-        );
+        }
     }
 
     /**
@@ -658,8 +687,7 @@ export class CoreSite {
      */
     protected callOrEnqueueRequest<T = unknown>(
         method: string,
-        // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-        data: any,
+        data: any, // eslint-disable-line @typescript-eslint/no-explicit-any
         preSets: CoreSiteWSPreSets,
         wsPreSets: CoreWSPreSets,
     ): Promise<T> {
@@ -677,13 +705,13 @@ export class CoreSite {
             }
         }
 
-        const request: RequestQueueItem = {
+        const request: RequestQueueItem<T> = {
             cacheId,
             method,
             data,
             preSets,
             wsPreSets,
-            deferred: CoreUtils.instance.promiseDefer<T>(),
+            deferred: CoreUtils.instance.promiseDefer(),
         };
 
         return this.enqueueRequest(request);
@@ -695,8 +723,7 @@ export class CoreSite {
      * @param request The request to enqueue.
      * @return Promise resolved with the response when the WS is called.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-    protected enqueueRequest(request: RequestQueueItem): Promise<any> {
+    protected enqueueRequest<T>(request: RequestQueueItem<T>): Promise<T> {
         this.requestQueue.push(request);
 
         if (this.requestQueue.length >= CoreSite.REQUEST_QUEUE_LIMIT) {
@@ -711,7 +738,7 @@ export class CoreSite {
     /**
      * Call the enqueued web service requests.
      */
-    protected processRequestQueue(): void {
+    protected async processRequestQueue(): Promise<void> {
         this.logger.debug(`Processing request queue (${this.requestQueue.length} requests)`);
 
         // Clear timeout if set.
@@ -726,16 +753,18 @@ export class CoreSite {
 
         if (requests.length == 1 && !CoreSite.REQUEST_QUEUE_FORCE_WS) {
             // Only one request, do a regular web service call.
-            CoreWS.instance.call(requests[0].method, requests[0].data, requests[0].wsPreSets).then((data) => {
+            try {
+                const data = await CoreWS.instance.call(requests[0].method, requests[0].data, requests[0].wsPreSets);
+
                 requests[0].deferred.resolve(data);
-            }).catch((error) => {
+            } catch (error) {
                 requests[0].deferred.reject(error);
-            });
+            }
 
             return;
         }
 
-        const data = {
+        const requestsData = {
             requests: requests.map((request) => {
                 const args = {};
                 const settings = {};
@@ -765,13 +794,18 @@ export class CoreSite {
 
         const wsPresets: CoreWSPreSets = {
             siteUrl: this.siteUrl,
-            wsToken: this.token,
+            wsToken: this.token || '',
         };
 
-        CoreWS.instance.call<CoreSiteCallExternalFunctionsResult>('tool_mobile_call_external_functions', data, wsPresets)
-                .then((data) => {
+        try {
+            const data = await CoreWS.instance.call<CoreSiteCallExternalFunctionsResult>(
+                'tool_mobile_call_external_functions',
+                requestsData,
+                wsPresets,
+            );
+
             if (!data || !data.responses) {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
             }
 
             requests.forEach((request, i) => {
@@ -781,9 +815,9 @@ export class CoreSite {
                     // Request not executed, enqueue again.
                     this.enqueueRequest(request);
                 } else if (response.error) {
-                    request.deferred.reject(CoreTextUtils.instance.parseJSON(response.exception));
+                    request.deferred.reject(CoreTextUtils.instance.parseJSON(response.exception || ''));
                 } else {
-                    let responseData = CoreTextUtils.instance.parseJSON(response.data);
+                    let responseData = response.data ? CoreTextUtils.instance.parseJSON(response.data) : {};
                     // Match the behaviour of CoreWSProvider.call when no response is expected.
                     const responseExpected = typeof wsPresets.responseExpected == 'undefined' || wsPresets.responseExpected;
                     if (!responseExpected && (responseData == null || responseData === '')) {
@@ -792,12 +826,12 @@ export class CoreSite {
                     request.deferred.resolve(responseData);
                 }
             });
-        }).catch((error) => {
+        } catch (error) {
             // Error not specific to a single request, reject all promises.
             requests.forEach((request) => {
                 request.deferred.reject(error);
             });
-        });
+        }
     }
 
     /**
@@ -812,7 +846,7 @@ export class CoreSite {
             return false;
         }
 
-        if (this.infos.functionsByName[method]) {
+        if (this.infos?.functionsByName?.[method]) {
             return true;
         }
 
@@ -831,7 +865,7 @@ export class CoreSite {
      * @param data Arguments to pass to the method.
      * @return Cache ID.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected getCacheId(method: string, data: any): string {
         return <string> Md5.hashAsciiStr(method + ':' + CoreUtils.instance.sortAndStringify(data));
     }
@@ -846,66 +880,70 @@ export class CoreSite {
      * @param originalData Arguments to pass to the method before being converted to strings.
      * @return Promise resolved with the WS response.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-    protected getFromCache<T = unknown>(method: string, data: any, preSets: CoreSiteWSPreSets, emergency?: boolean): Promise<T> {
+    protected async getFromCache<T = unknown>(
+        method: string,
+        data: any, // eslint-disable-line @typescript-eslint/no-explicit-any
+        preSets: CoreSiteWSPreSets,
+        emergency?: boolean,
+    ): Promise<T> {
         if (!this.db || !preSets.getFromCache) {
-            return Promise.reject(new CoreError('Get from cache is disabled.'));
+            throw new CoreError('Get from cache is disabled.');
         }
 
         const id = this.getCacheId(method, data);
-        // eslint-disable-next-line @typescript-eslint/no-explicit-any
-        let promise: Promise<any>;
+        let entry: CoreSiteWSCacheRecord | undefined;
 
         if (preSets.getCacheUsingCacheKey || (emergency && preSets.getEmergencyCacheUsingCacheKey)) {
-            promise = this.db.getRecords<any>(CoreSite.WS_CACHE_TABLE, { key: preSets.cacheKey }).then((entries) => {
-                if (!entries.length) {
-                    // Cache key not found, get by params sent.
-                    return this.db.getRecord(CoreSite.WS_CACHE_TABLE, { id });
-                } else if (entries.length > 1) {
+            const entries = await this.db.getRecords<CoreSiteWSCacheRecord>(CoreSite.WS_CACHE_TABLE, { key: preSets.cacheKey });
+
+            if (!entries.length) {
+                // Cache key not found, get by params sent.
+                entry = await this.db!.getRecord(CoreSite.WS_CACHE_TABLE, { id });
+            } else {
+                if (entries.length > 1) {
                     // More than one entry found. Search the one with same ID as this call.
-                    for (let i = 0, len = entries.length; i < len; i++) {
-                        const entry = entries[i];
-                        if (entry.id == id) {
-                            return entry;
-                        }
-                    }
+                    entry = entries.find((entry) => entry.id == id);
                 }
 
-                return entries[0];
-            });
+                if (!entry) {
+                    entry = entries[0];
+                }
+            }
         } else {
-            promise = this.db.getRecord(CoreSite.WS_CACHE_TABLE, { id });
+            entry = await this.db!.getRecord(CoreSite.WS_CACHE_TABLE, { id });
         }
 
-        return promise.then((entry) => {
-            const now = Date.now();
-            let expirationTime: number;
+        if (typeof entry == 'undefined') {
+            throw new CoreError('Cache entry not valid.');
+        }
 
-            preSets.omitExpires = preSets.omitExpires || preSets.forceOffline || !CoreApp.instance.isOnline();
+        const now = Date.now();
+        let expirationTime: number | undefined;
 
-            if (!preSets.omitExpires) {
-                expirationTime = entry.expirationTime + this.getExpirationDelay(preSets.updateFrequency);
+        preSets.omitExpires = preSets.omitExpires || preSets.forceOffline || !CoreApp.instance.isOnline();
 
-                if (now > expirationTime) {
-                    this.logger.debug('Cached element found, but it is expired');
+        if (!preSets.omitExpires) {
+            expirationTime = entry.expirationTime + this.getExpirationDelay(preSets.updateFrequency);
 
-                    return Promise.reject(new CoreError('Cache entry is expired.'));
-                }
+            if (now > expirationTime!) {
+                this.logger.debug('Cached element found, but it is expired');
+
+                throw new CoreError('Cache entry is expired.');
+            }
+        }
+
+        if (typeof entry.data != 'undefined') {
+            if (!expirationTime) {
+                this.logger.info(`Cached element found, id: ${id}. Expiration time ignored.`);
+            } else {
+                const expires = (expirationTime - now) / 1000;
+                this.logger.info(`Cached element found, id: ${id}. Expires in expires in ${expires} seconds`);
             }
 
-            if (typeof entry != 'undefined' && typeof entry.data != 'undefined') {
-                if (!expirationTime) {
-                    this.logger.info(`Cached element found, id: ${id}. Expiration time ignored.`);
-                } else {
-                    const expires = (expirationTime - now) / 1000;
-                    this.logger.info(`Cached element found, id: ${id}. Expires in expires in ${expires} seconds`);
-                }
+            return <T> CoreTextUtils.instance.parseJSON(entry.data, {});
+        }
 
-                return <T> CoreTextUtils.instance.parseJSON(entry.data, {});
-            }
-
-            return Promise.reject(new CoreError('Cache entry not valid.'));
-        });
+        throw new CoreError('Cache entry not valid.');
     }
 
     /**
@@ -923,8 +961,10 @@ export class CoreSite {
             extraClause = ' AND componentId = ?';
         }
 
-        const size = <number> await this.db.getFieldSql('SELECT SUM(length(data)) FROM ' + CoreSite.WS_CACHE_TABLE +
-                ' WHERE component = ?' + extraClause, params);
+        const size = <number> await this.getDb().getFieldSql(
+            'SELECT SUM(length(data)) FROM ' + CoreSite.WS_CACHE_TABLE + ' WHERE component = ?' + extraClause,
+            params,
+        );
 
         return size;
     }
@@ -938,7 +978,7 @@ export class CoreSite {
      * @param preSets Extra options.
      * @return Promise resolved when the response is saved.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected async saveToCache(method: string, data: any, response: any, preSets: CoreSiteWSPreSets): Promise<void> {
         if (!this.db) {
             throw new CoreError('Site DB not initialized.');
@@ -981,7 +1021,7 @@ export class CoreSite {
      * @param allCacheKey True to delete all entries with the cache key, false to delete only by ID.
      * @return Promise resolved when the entries are deleted.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected async deleteFromCache(method: string, data: any, preSets: CoreSiteWSPreSets, allCacheKey?: boolean): Promise<void> {
         if (!this.db) {
             throw new CoreError('Site DB not initialized.');
@@ -1042,7 +1082,7 @@ export class CoreSite {
 
         return CoreWS.instance.uploadFile<T>(filePath, options, {
             siteUrl: this.siteUrl,
-            wsToken: this.token,
+            wsToken: this.token || '',
         }, onProgress);
     }
 
@@ -1144,7 +1184,7 @@ export class CoreSite {
         const accessKey = this.tokenPluginFileWorks || typeof this.tokenPluginFileWorks == 'undefined' ?
             this.infos && this.infos.userprivateaccesskey : undefined;
 
-        return CoreUrlUtils.instance.fixPluginfileURL(url, this.token, this.siteUrl, accessKey);
+        return CoreUrlUtils.instance.fixPluginfileURL(url, this.token || '', this.siteUrl, accessKey);
     }
 
     /**
@@ -1162,7 +1202,7 @@ export class CoreSite {
      * @return Promise to be resolved when the DB is deleted.
      */
     async deleteFolder(): Promise<void> {
-        if (!CoreFile.instance.isAvailable()) {
+        if (!CoreFile.instance.isAvailable() || !this.id) {
             return;
         }
 
@@ -1178,7 +1218,7 @@ export class CoreSite {
      * @return Promise resolved with the site space usage (size).
      */
     getSpaceUsage(): Promise<number> {
-        if (CoreFile.instance.isAvailable()) {
+        if (CoreFile.instance.isAvailable() && this.id) {
             const siteFolderPath = CoreFile.instance.getSiteFolder(this.id);
 
             return CoreFile.instance.getDirectorySize(siteFolderPath).catch(() => 0);
@@ -1195,7 +1235,7 @@ export class CoreSite {
      * @return Promise resolved with the total size of all data in the cache table (bytes)
      */
     async getCacheUsage(): Promise<number> {
-        const size = <number> await this.db.getFieldSql('SELECT SUM(length(data)) FROM ' + CoreSite.WS_CACHE_TABLE);
+        const size = <number> await this.getDb().getFieldSql('SELECT SUM(length(data)) FROM ' + CoreSite.WS_CACHE_TABLE);
 
         return size;
     }
@@ -1219,7 +1259,7 @@ export class CoreSite {
      * @return Promise resolved with the Moodle docs URL.
      */
     getDocsUrl(page?: string): Promise<string> {
-        const release = this.infos.release ? this.infos.release : undefined;
+        const release = this.infos?.release ? this.infos.release : undefined;
 
         return CoreUrlUtils.instance.getDocsUrl(release, page);
     }
@@ -1369,37 +1409,43 @@ export class CoreSite {
      *
      * @return Promise resolved with public config. Rejected with an object if error, see CoreWSProvider.callAjax.
      */
-    getPublicConfig(): Promise<CoreSitePublicConfigResponse> {
+    async getPublicConfig(): Promise<CoreSitePublicConfigResponse> {
         const preSets: CoreWSAjaxPreSets = {
             siteUrl: this.siteUrl,
         };
 
-        return CoreWS.instance.callAjax('tool_mobile_get_public_config', {}, preSets).catch((error) => {
+        let config: CoreSitePublicConfigResponse | undefined;
+
+        try {
+            config = await CoreWS.instance.callAjax('tool_mobile_get_public_config', {}, preSets);
+        } catch (error) {
             if ((!this.getInfo() || this.isVersionGreaterEqualThan('3.8')) && error && error.errorcode == 'codingerror') {
                 // This error probably means that there is a redirect in the site. Try to use a GET request.
                 preSets.noLogin = true;
                 preSets.useGet = true;
 
-                return CoreWS.instance.callAjax('tool_mobile_get_public_config', {}, preSets).catch((error2) => {
+                try {
+                    config = await CoreWS.instance.callAjax('tool_mobile_get_public_config', {}, preSets);
+                } catch (error2) {
                     if (this.getInfo() && this.isVersionGreaterEqualThan('3.8')) {
                         // GET is supported, return the second error.
-                        return Promise.reject(error2);
+                        throw error2;
                     } else {
                         // GET not supported or we don't know if it's supported. Return first error.
-                        return Promise.reject(error);
+                        throw error;
                     }
-                });
+                }
             }
 
-            return Promise.reject(error);
-        }).then((config: CoreSitePublicConfigResponse) => {
-            // Use the wwwroot returned by the server.
-            if (config.httpswwwroot) {
-                this.siteUrl = config.httpswwwroot;
-            }
+            throw error;
+        }
 
-            return config;
-        });
+        // Use the wwwroot returned by the server.
+        if (config!.httpswwwroot) {
+            this.siteUrl = config!.httpswwwroot;
+        }
+
+        return config!;
     }
 
     /**
@@ -1446,8 +1492,11 @@ export class CoreSite {
      * @param alertMessage If defined, an alert will be shown before opening the inappbrowser.
      * @return Promise resolved when done.
      */
-    async openInAppWithAutoLoginIfSameSite(url: string, options?: InAppBrowserOptions, alertMessage?: string):
-            Promise<InAppBrowserObject> {
+    async openInAppWithAutoLoginIfSameSite(
+        url: string,
+        options?: InAppBrowserOptions,
+        alertMessage?: string,
+    ): Promise<InAppBrowserObject> {
         const iabInstance = <InAppBrowserObject> await this.openWithAutoLoginIfSameSite(true, url, options, alertMessage);
 
         return iabInstance;
@@ -1462,34 +1511,33 @@ export class CoreSite {
      * @param alertMessage If defined, an alert will be shown before opening the browser/inappbrowser.
      * @return Promise resolved when done. Resolve param is returned only if inApp=true.
      */
-    openWithAutoLogin(inApp: boolean, url: string, options?: InAppBrowserOptions, alertMessage?: string):
-            Promise<InAppBrowserObject | void> {
+    async openWithAutoLogin(
+        inApp: boolean,
+        url: string,
+        options?: InAppBrowserOptions,
+        alertMessage?: string,
+    ): Promise<InAppBrowserObject | void> {
         // Get the URL to open.
-        return this.getAutoLoginUrl(url).then((url) => {
-            if (!alertMessage) {
-                // Just open the URL.
-                if (inApp) {
-                    return CoreUtils.instance.openInApp(url, options);
-                } else {
-                    return CoreUtils.instance.openInBrowser(url);
-                }
-            }
+        url = await this.getAutoLoginUrl(url);
 
+        if (alertMessage) {
             // Show an alert first.
-            return CoreDomUtils.instance.showAlert(Translate.instance.instant('core.notice'), alertMessage, undefined, 3000)
-                .then(() => new Promise<InAppBrowserObject | void>(() => {
-                    // @todo
-                    // const subscription = alert.didDismiss.subscribe(() => {
-                    //     subscription && subscription.unsubscribe();
+            const alert = await CoreDomUtils.instance.showAlert(
+                Translate.instance.instant('core.notice'),
+                alertMessage,
+                undefined,
+                3000,
+            );
 
-                    //     if (inApp) {
-                    //         resolve(CoreUtils.instance.openInApp(url, options));
-                    //     } else {
-                    //         resolve(CoreUtils.instance.openInBrowser(url));
-                    //     }
-                    // });
-                }));
-        });
+            await alert.onDidDismiss();
+        }
+
+        // Open the URL.
+        if (inApp) {
+            return CoreUtils.instance.openInApp(url, options);
+        } else {
+            return CoreUtils.instance.openInBrowser(url);
+        }
     }
 
     /**
@@ -1501,8 +1549,12 @@ export class CoreSite {
      * @param alertMessage If defined, an alert will be shown before opening the browser/inappbrowser.
      * @return Promise resolved when done. Resolve param is returned only if inApp=true.
      */
-    openWithAutoLoginIfSameSite(inApp: boolean, url: string, options?: InAppBrowserOptions, alertMessage?: string):
-            Promise<InAppBrowserObject | void> {
+    async openWithAutoLoginIfSameSite(
+        inApp: boolean,
+        url: string,
+        options?: InAppBrowserOptions,
+        alertMessage?: string,
+    ): Promise<InAppBrowserObject | void> {
         if (this.containsUrl(url)) {
             return this.openWithAutoLogin(inApp, url, options, alertMessage);
         } else {
@@ -1522,6 +1574,8 @@ export class CoreSite {
      * @param ignoreCache True if it should ignore cached data.
      * @return Promise resolved with site config.
      */
+    getConfig(name?: undefined, ignoreCache?: boolean): Promise<CoreSiteConfig>;
+    getConfig(name: string, ignoreCache?: boolean): Promise<string>;
     getConfig(name?: string, ignoreCache?: boolean): Promise<string | CoreSiteConfig> {
         const preSets: CoreSiteWSPreSets = {
             cacheKey: this.getConfigCacheKey(),
@@ -1578,7 +1632,9 @@ export class CoreSite {
      * @param name Name of the setting to get. If not set, all settings will be returned.
      * @return Site config or a specific setting.
      */
-    getStoredConfig(name?: string): string | CoreSiteConfig {
+    getStoredConfig(): CoreSiteConfig | undefined;
+    getStoredConfig(name: string): string | undefined;
+    getStoredConfig(name?: string): string | CoreSiteConfig | undefined {
         if (!this.config) {
             return;
         }
@@ -1597,7 +1653,7 @@ export class CoreSite {
      * @return Whether it's disabled.
      */
     isFeatureDisabled(name: string): boolean {
-        const disabledFeatures = <string> this.getStoredConfig('tool_mobile_disabledfeatures');
+        const disabledFeatures = this.getStoredConfig('tool_mobile_disabledfeatures');
         if (!disabledFeatures) {
             return false;
         }
@@ -1645,7 +1701,13 @@ export class CoreSite {
      * it's the last released major version.
      */
     isVersionGreaterEqualThan(versions: string | string[]): boolean {
-        const siteVersion = parseInt(this.getInfo().version, 10);
+        const info = this.getInfo();
+
+        if (!info || !info.version) {
+            return false;
+        }
+
+        const siteVersion = Number(info.version);
 
         if (Array.isArray(versions)) {
             if (!versions.length) {
@@ -1679,26 +1741,27 @@ export class CoreSite {
      * @param showModal Whether to show a loading modal.
      * @return Promise resolved with the converted URL.
      */
-    getAutoLoginUrl(url: string, showModal: boolean = true): Promise<string> {
+    async getAutoLoginUrl(url: string, showModal: boolean = true): Promise<string> {
         if (!this.privateToken || !this.wsAvailable('tool_mobile_get_autologin_key') || (this.lastAutoLogin &&
                 CoreTimeUtils.instance.timestamp() - this.lastAutoLogin < CoreConstants.SECONDS_MINUTE * 6)) {
             // No private token, WS not available or last auto-login was less than 6 minutes ago. Don't change the URL.
-
-            return Promise.resolve(url);
+            return url;
         }
 
         const userId = this.getUserId();
         const params = {
             privatetoken: this.privateToken,
         };
-        let modal;
+        let modal: CoreIonLoadingElement | undefined;
 
         if (showModal) {
-            modal = CoreDomUtils.instance.showModalLoading();
+            modal = await CoreDomUtils.instance.showModalLoading();
         }
 
-        // Use write to not use cache.
-        return this.write<CoreSiteAutologinKeyResult>('tool_mobile_get_autologin_key', params).then((data) => {
+        try {
+            // Use write to not use cache.
+            const data = await this.write<CoreSiteAutologinKeyResult>('tool_mobile_get_autologin_key', params);
+
             if (!data.autologinurl || !data.key) {
                 // Not valid data, return the same URL.
                 return url;
@@ -1707,13 +1770,12 @@ export class CoreSite {
             this.lastAutoLogin = CoreTimeUtils.instance.timestamp();
 
             return data.autologinurl + '?userid=' + userId + '&key=' + data.key + '&urltogo=' + encodeURIComponent(url);
-        }).catch(() =>
-
+        } catch (error) {
             // Couldn't get autologin key, return the same URL.
-            url,
-        ).finally(() => {
-            modal && modal.dismiss();
-        });
+            return url;
+        } finally {
+            modal?.dismiss();
+        }
     }
 
     /**
@@ -1733,7 +1795,7 @@ export class CoreSite {
 
         if (typeof this.MOODLE_RELEASES[data.major] == 'undefined') {
             // Major version not found. Use the last one.
-            data.major = Object.keys(this.MOODLE_RELEASES).pop();
+            data.major = Object.keys(this.MOODLE_RELEASES).pop()!;
         }
 
         return this.MOODLE_RELEASES[data.major] + data.minor;
@@ -1790,7 +1852,7 @@ export class CoreSite {
      * @return Promise resolved when done.
      */
     async deleteSiteConfig(name: string): Promise<void> {
-        await this.db.deleteRecords(CoreSite.CONFIG_TABLE, { name });
+        await this.getDb().deleteRecords(CoreSite.CONFIG_TABLE, { name });
     }
 
     /**
@@ -1800,15 +1862,18 @@ export class CoreSite {
      * @param defaultValue Default value to use if the entry is not found.
      * @return Resolves upon success along with the config data. Reject on failure.
      */
-    getLocalSiteConfig<T extends number | string>(name: string, defaultValue?: T): Promise<T> {
-        return this.db.getRecord<CoreSiteConfigDBRecord>(CoreSite.CONFIG_TABLE, { name }).then((entry) => <T> entry.value)
-                .catch((error) => {
+    async getLocalSiteConfig<T extends number | string>(name: string, defaultValue?: T): Promise<T> {
+        try {
+            const entry = await this.getDb().getRecord<CoreSiteConfigDBRecord>(CoreSite.CONFIG_TABLE, { name });
+
+            return <T> entry.value;
+        } catch (error) {
             if (typeof defaultValue != 'undefined') {
                 return defaultValue;
             }
 
-            return Promise.reject(error);
-        });
+            throw error;
+        }
     }
 
     /**
@@ -1819,7 +1884,7 @@ export class CoreSite {
      * @return Promise resolved when done.
      */
     async setLocalSiteConfig(name: string, value: number | string): Promise<void> {
-        await this.db.insertRecord(CoreSite.CONFIG_TABLE, { name, value });
+        await this.getDb().insertRecord(CoreSite.CONFIG_TABLE, { name, value });
     }
 
     /**
@@ -1829,6 +1894,7 @@ export class CoreSite {
      * @return Expiration delay.
      */
     getExpirationDelay(updateFrequency?: number): number {
+        updateFrequency = updateFrequency || CoreSite.FREQUENCY_USUALLY;
         let expirationDelay = this.UPDATE_FREQUENCIES[updateFrequency] || this.UPDATE_FREQUENCIES[CoreSite.FREQUENCY_USUALLY];
 
         if (CoreApp.instance.isNetworkAccessLimited()) {
@@ -2010,15 +2076,14 @@ export type LocalMobileResponse = {
 /**
  * Info of a request waiting in the queue.
  */
-type RequestQueueItem = {
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type RequestQueueItem<T = any> = {
     cacheId: string;
     method: string;
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-    data: any;
+    data: any; // eslint-disable-line @typescript-eslint/no-explicit-any
     preSets: CoreSiteWSPreSets;
     wsPreSets: CoreWSPreSets;
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
-    deferred: PromiseDefer<any>;
+    deferred: PromiseDefer<T>;
 };
 
 /**
@@ -2166,3 +2231,12 @@ export type CoreSiteConfigDBRecord = {
     name: string;
     value: string | number;
 };
+
+export type CoreSiteWSCacheRecord = {
+    id: string;
+    data: string;
+    expirationTime: number;
+    key?: string;
+    component?: string;
+    componentId?: number;
+};
diff --git a/src/app/classes/sqlitedb.ts b/src/app/classes/sqlitedb.ts
index a46729325..14fff4066 100644
--- a/src/app/classes/sqlitedb.ts
+++ b/src/app/classes/sqlitedb.ts
@@ -472,7 +472,7 @@ export class SQLiteDB {
      * @return List of params.
      */
     protected formatDataToSQLParams(data: SQLiteDBRecordValues): SQLiteDBRecordValue[] {
-        return Object.keys(data).map((key) => data[key]);
+        return Object.keys(data).map((key) => data[key]!);
     }
 
     /**
@@ -1087,7 +1087,7 @@ export class SQLiteDB {
 }
 
 export type SQLiteDBRecordValues = {
-    [key in string ]: SQLiteDBRecordValue;
+    [key in string ]: SQLiteDBRecordValue | undefined;
 };
 
 export type SQLiteDBQueryParams = {
diff --git a/src/app/components/icon/icon.ts b/src/app/components/icon/icon.ts
index eea96b488..830ed8375 100644
--- a/src/app/components/icon/icon.ts
+++ b/src/app/components/icon/icon.ts
@@ -38,7 +38,7 @@ export class CoreIconComponent implements OnChanges, OnDestroy {
     @Input() ios?: string;
 
     // FontAwesome params.
-    @Input('fixed-width') fixedWidth: boolean;
+    @Input('fixed-width') fixedWidth?: boolean; // eslint-disable-line @angular-eslint/no-input-rename
 
     @Input() label?: string;
     @Input() flipRtl?: boolean; // Whether to flip the icon in RTL. Defaults to false.
@@ -48,7 +48,7 @@ export class CoreIconComponent implements OnChanges, OnDestroy {
 
     constructor(el: ElementRef) {
         this.element = el.nativeElement;
-        this.newElement = this.element
+        this.newElement = this.element;
     }
 
     /**
diff --git a/src/app/components/loading/loading.ts b/src/app/components/loading/loading.ts
index baf58d6cf..6ce15ee24 100644
--- a/src/app/components/loading/loading.ts
+++ b/src/app/components/loading/loading.ts
@@ -48,9 +48,9 @@ export class CoreLoadingComponent implements OnInit, OnChanges, AfterViewInit {
 
     @Input() hideUntil: unknown; // Determine when should the contents be shown.
     @Input() message?: string; // Message to show while loading.
-    @ViewChild('content') content: ElementRef;
+    @ViewChild('content') content?: ElementRef;
 
-    protected uniqueId: string;
+    protected uniqueId!: string;
     protected element: HTMLElement; // Current element.
 
     constructor(element: ElementRef) {
diff --git a/src/app/components/show-password/show-password.ts b/src/app/components/show-password/show-password.ts
index e2d79fa4d..12dafefe4 100644
--- a/src/app/components/show-password/show-password.ts
+++ b/src/app/components/show-password/show-password.ts
@@ -40,16 +40,16 @@ import { CoreUtils } from '@services/utils/utils';
 })
 export class CoreShowPasswordComponent implements OnInit, AfterViewInit {
 
-    @Input() name: string; // Name of the input affected.
+    @Input() name?: string; // Name of the input affected.
     @Input() initialShown?: boolean | string; // Whether the password should be shown at start.
-    @ContentChild(IonInput) ionInput: IonInput;
+    @ContentChild(IonInput) ionInput?: IonInput;
 
-    shown: boolean; // Whether the password is shown.
-    label: string; // Label for the button to show/hide.
-    iconName: string; // Name of the icon of the button to show/hide.
+    shown!: boolean; // Whether the password is shown.
+    label?: string; // Label for the button to show/hide.
+    iconName?: string; // Name of the icon of the button to show/hide.
     selector = ''; // Selector to identify the input.
 
-    protected input: HTMLInputElement; // Input affected.
+    protected input?: HTMLInputElement | null; // Input affected.
     protected element: HTMLElement; // Current element.
 
     constructor(element: ElementRef) {
@@ -84,7 +84,7 @@ export class CoreShowPasswordComponent implements OnInit, AfterViewInit {
         }
 
         // Search the input.
-        this.input = this.element.querySelector(this.selector);
+        this.input = <HTMLInputElement> this.element.querySelector(this.selector);
 
         if (this.input) {
             // Input found. Set the right type.
@@ -128,7 +128,7 @@ export class CoreShowPasswordComponent implements OnInit, AfterViewInit {
         if (isFocused && CoreApp.instance.isAndroid()) {
             // In Android, the keyboard is closed when the input type changes. Focus it again.
             setTimeout(() => {
-                CoreDomUtils.instance.focusElement(this.input);
+                CoreDomUtils.instance.focusElement(this.input!);
             }, 400);
         }
     }
diff --git a/src/app/core/constants.ts b/src/app/core/constants.ts
index def5471dd..41c7c1b3f 100644
--- a/src/app/core/constants.ts
+++ b/src/app/core/constants.ts
@@ -39,7 +39,7 @@ export class CoreConstants {
     static readonly DOWNLOAD_THRESHOLD = 10485760; // 10MB.
     static readonly MINIMUM_FREE_SPACE = 10485760; // 10MB.
     static readonly IOS_FREE_SPACE_THRESHOLD = 524288000; // 500MB.
-    static readonly DONT_SHOW_ERROR = 'CoreDontShowError';
+    static readonly DONT_SHOW_ERROR = 'CoreDontShowError'; // @deprecated since 3.9.5. Use CoreSilentError instead.
     static readonly NO_SITE_ID = 'NoSite';
 
     // Settings constants.
diff --git a/src/app/core/emulator/classes/sqlitedb.ts b/src/app/core/emulator/classes/sqlitedb.ts
index b327029fd..055944f71 100644
--- a/src/app/core/emulator/classes/sqlitedb.ts
+++ b/src/app/core/emulator/classes/sqlitedb.ts
@@ -35,6 +35,7 @@ export class SQLiteDBMock extends SQLiteDB {
      *
      * @return Promise resolved when done.
      */
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     close(): Promise<any> {
         // WebSQL databases aren't closed.
         return Promise.resolve();
@@ -45,6 +46,7 @@ export class SQLiteDBMock extends SQLiteDB {
      *
      * @return Promise resolved when done.
      */
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     async emptyDatabase(): Promise<any> {
         await this.ready();
 
@@ -89,6 +91,7 @@ export class SQLiteDBMock extends SQLiteDB {
      * @param params Query parameters.
      * @return Promise resolved with the result.
      */
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     async execute(sql: string, params?: any[]): Promise<any> {
         await this.ready();
 
@@ -115,6 +118,7 @@ export class SQLiteDBMock extends SQLiteDB {
      * @param sqlStatements SQL statements to execute.
      * @return Promise resolved with the result.
      */
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     async executeBatch(sqlStatements: any[]): Promise<any> {
         await this.ready();
 
@@ -148,6 +152,7 @@ export class SQLiteDBMock extends SQLiteDB {
                     }));
                 });
 
+                // eslint-disable-next-line promise/catch-or-return
                 Promise.all(promises).then(resolve, reject);
             });
         });
@@ -158,6 +163,7 @@ export class SQLiteDBMock extends SQLiteDB {
      */
     init(): void {
         // This DB is for desktop apps, so use a big size to be sure it isn't filled.
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
         this.db = (<any> window).openDatabase(this.name, '1.0', this.name, 500 * 1024 * 1024);
         this.promise = Promise.resolve();
     }
diff --git a/src/app/core/login/pages/credentials/credentials.page.ts b/src/app/core/login/pages/credentials/credentials.page.ts
index 57fa2913e..3bcc2f00e 100644
--- a/src/app/core/login/pages/credentials/credentials.page.ts
+++ b/src/app/core/login/pages/credentials/credentials.page.ts
@@ -36,27 +36,27 @@ import { CoreEvents, CoreEventsProvider } from '@/app/services/events';
 })
 export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
 
-    @ViewChild('credentialsForm') formElement: ElementRef;
+    @ViewChild('credentialsForm') formElement?: ElementRef;
 
-    credForm: FormGroup;
-    siteUrl: string;
+    credForm!: FormGroup;
+    siteUrl!: string;
     siteChecked = false;
-    siteName: string;
-    logoUrl: string;
-    authInstructions: string;
-    canSignup: boolean;
-    identityProviders: CoreSiteIdentityProvider[];
+    siteName?: string;
+    logoUrl?: string;
+    authInstructions?: string;
+    canSignup?: boolean;
+    identityProviders?: CoreSiteIdentityProvider[];
     pageLoaded = false;
     isBrowserSSO = false;
     isFixedUrlSet = false;
     showForgottenPassword = true;
     showScanQR: boolean;
 
-    protected siteConfig: CoreSitePublicConfigResponse;
+    protected siteConfig?: CoreSitePublicConfigResponse;
     protected eventThrown = false;
     protected viewLeft = false;
-    protected siteId: string;
-    protected urlToOpen: string;
+    protected siteId?: string;
+    protected urlToOpen?: string;
 
     constructor(
         protected fb: FormBuilder,
@@ -82,8 +82,8 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
     ngOnInit(): void {
         this.route.queryParams.subscribe(params => {
             this.siteUrl = params['siteUrl'];
-            this.siteName = params['siteName'] || null;
-            this.logoUrl = !CoreConfigConstants.forceLoginLogo && params['logoUrl'] || null;
+            this.siteName = params['siteName'] || undefined;
+            this.logoUrl = !CoreConfigConstants.forceLoginLogo && params['logoUrl'] || undefined;
             this.siteConfig = params['siteConfig'];
             this.urlToOpen = params['urlToOpen'];
 
@@ -138,7 +138,11 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
                 // Check that there's no SSO authentication ongoing and the view hasn't changed.
                 if (!CoreApp.instance.isSSOAuthenticationOngoing() && !this.viewLeft) {
                     CoreLoginHelper.instance.confirmAndOpenBrowserForSSOLogin(
-                        result.siteUrl, result.code, result.service, result.config?.launchurl);
+                        result.siteUrl,
+                        result.code,
+                        result.service,
+                        result.config?.launchurl,
+                    );
                 }
             } else {
                 this.isBrowserSSO = false;
@@ -171,7 +175,7 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
                 CoreEvents.instance.trigger(CoreEventsProvider.LOGIN_SITE_CHECKED, { config: this.siteConfig });
             }
         } else {
-            this.authInstructions = null;
+            this.authInstructions = undefined;
             this.canSignup = false;
             this.identityProviders = [];
         }
@@ -261,7 +265,11 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
      */
     forgottenPassword(): void {
         CoreLoginHelper.instance.forgottenPasswordClicked(
-            this.navCtrl, this.siteUrl, this.credForm.value.username, this.siteConfig);
+            this.navCtrl,
+            this.siteUrl,
+            this.credForm.value.username,
+            this.siteConfig,
+        );
     }
 
     /**
@@ -270,7 +278,7 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
      * @param provider The provider that was clicked.
      */
     oauthClicked(provider: CoreSiteIdentityProvider): void {
-        if (!CoreLoginHelper.instance.openBrowserForOAuthLogin(this.siteUrl, provider, this.siteConfig.launchurl)) {
+        if (!CoreLoginHelper.instance.openBrowserForOAuthLogin(this.siteUrl, provider, this.siteConfig?.launchurl)) {
             CoreDomUtils.instance.showErrorModal('Invalid data.');
         }
     }
@@ -289,8 +297,10 @@ export class CoreLoginCredentialsPage implements OnInit, OnDestroy {
         // Show some instructions first.
         CoreDomUtils.instance.showAlertWithOptions({
             header: Translate.instance.instant('core.login.faqwhereisqrcode'),
-            message: Translate.instance.instant('core.login.faqwhereisqrcodeanswer',
-                { $image: CoreLoginHelperProvider.FAQ_QRCODE_IMAGE_HTML }),
+            message: Translate.instance.instant(
+                'core.login.faqwhereisqrcodeanswer',
+                { $image: CoreLoginHelperProvider.FAQ_QRCODE_IMAGE_HTML },
+            ),
             buttons: [
                 {
                     text: Translate.instance.instant('core.cancel'),
diff --git a/src/app/core/login/pages/init/init.page.ts b/src/app/core/login/pages/init/init.page.ts
index 006ec48c6..762be4743 100644
--- a/src/app/core/login/pages/init/init.page.ts
+++ b/src/app/core/login/pages/init/init.page.ts
@@ -34,44 +34,44 @@ export class CoreLoginInitPage implements OnInit {
     /**
      * Initialize the component.
      */
-    ngOnInit(): void {
+    async ngOnInit(): Promise<void> {
         // Wait for the app to be ready.
-        CoreInit.instance.ready().then(() => {
-            // Check if there was a pending redirect.
-            const redirectData = CoreApp.instance.getRedirect();
-            if (redirectData.siteId) {
-                // Unset redirect data.
-                CoreApp.instance.storeRedirect('', '', {});
+        await CoreInit.instance.ready();
 
-                // Only accept the redirect if it was stored less than 20 seconds ago.
-                if (Date.now() - redirectData.timemodified < 20000) {
-                    // if (redirectData.siteId != CoreConstants.NO_SITE_ID) {
-                    //     // The redirect is pointing to a site, load it.
-                    //     return this.sitesProvider.loadSite(redirectData.siteId, redirectData.page, redirectData.params)
-                    //             .then((loggedIn) => {
+        // Check if there was a pending redirect.
+        const redirectData = CoreApp.instance.getRedirect();
+        if (redirectData.siteId) {
+            // Unset redirect data.
+            CoreApp.instance.storeRedirect('', '', {});
 
-                    //         if (loggedIn) {
-                    //             return this.loginHelper.goToSiteInitialPage(this.navCtrl, redirectData.page, redirectData.params,
-                    //                     { animate: false });
-                    //         }
-                    //     }).catch(() => {
-                    //         // Site doesn't exist.
-                    //         return this.loadPage();
-                    //     });
-                    // } else {
-                    //     // No site to load, open the page.
-                    //     return this.loginHelper.goToNoSitePage(this.navCtrl, redirectData.page, redirectData.params);
-                    // }
-                }
+            // Only accept the redirect if it was stored less than 20 seconds ago.
+            if (redirectData.timemodified && Date.now() - redirectData.timemodified < 20000) {
+                // if (redirectData.siteId != CoreConstants.NO_SITE_ID) {
+                //     // The redirect is pointing to a site, load it.
+                //     return this.sitesProvider.loadSite(redirectData.siteId, redirectData.page, redirectData.params)
+                //             .then((loggedIn) => {
+
+                //         if (loggedIn) {
+                //             return this.loginHelper.goToSiteInitialPage(this.navCtrl, redirectData.page, redirectData.params,
+                //                     { animate: false });
+                //         }
+                //     }).catch(() => {
+                //         // Site doesn't exist.
+                //         return this.loadPage();
+                //     });
+                // } else {
+                //     // No site to load, open the page.
+                //     return this.loginHelper.goToNoSitePage(this.navCtrl, redirectData.page, redirectData.params);
+                // }
             }
+        }
 
-            return this.loadPage();
-        }).then(() => {
-            // If we hide the splash screen now, the init view is still seen for an instant. Wait a bit to make sure it isn't seen.
-            setTimeout(() => {
-                SplashScreen.instance.hide();
-            }, 100);
-        });
+        await this.loadPage();
+
+        // If we hide the splash screen now, the init view is still seen for an instant. Wait a bit to make sure it isn't seen.
+        setTimeout(() => {
+            SplashScreen.instance.hide();
+        }, 100);
     }
 
     /**
diff --git a/src/app/core/login/pages/site/site.page.ts b/src/app/core/login/pages/site/site.page.ts
index 465181352..432c52a12 100644
--- a/src/app/core/login/pages/site/site.page.ts
+++ b/src/app/core/login/pages/site/site.page.ts
@@ -40,11 +40,11 @@ import { NavController } from '@ionic/angular';
 })
 export class CoreLoginSitePage implements OnInit {
 
-    @ViewChild('siteFormEl') formElement: ElementRef;
+    @ViewChild('siteFormEl') formElement?: ElementRef;
 
     siteForm: FormGroup;
-    fixedSites: CoreLoginSiteInfoExtended[];
-    filteredSites: CoreLoginSiteInfoExtended[];
+    fixedSites?: CoreLoginSiteInfoExtended[];
+    filteredSites?: CoreLoginSiteInfoExtended[];
     siteSelector = 'sitefinder';
     showKeyboard = false;
     filter = '';
@@ -53,7 +53,7 @@ export class CoreLoginSitePage implements OnInit {
     loadingSites = false;
     searchFunction: (search: string) => void;
     showScanQR: boolean;
-    enteredSiteUrl: CoreLoginSiteInfoExtended;
+    enteredSiteUrl?: CoreLoginSiteInfoExtended;
     siteFinderSettings: SiteFinderSettings;
 
     constructor(
@@ -95,10 +95,10 @@ export class CoreLoginSitePage implements OnInit {
 
             if (search.length >= 3) {
                 // Update the sites list.
-                this.sites = await CoreSites.instance.findSites(search);
+                const sites = await CoreSites.instance.findSites(search);
 
                 // Add UI tweaks.
-                this.sites = this.extendCoreLoginSiteInfo(this.sites);
+                this.sites = this.extendCoreLoginSiteInfo(<CoreLoginSiteInfoExtended[]> sites);
 
                 this.hasSites = !!this.sites.length;
             } else {
@@ -201,7 +201,7 @@ export class CoreLoginSitePage implements OnInit {
             let valid = value.length >= 3 && CoreUrl.isValidMoodleUrl(value);
 
             if (!valid) {
-                const demo = !!this.getDemoSiteData(value);
+                const demo = !!CoreSites.instance.getDemoSiteData(value);
 
                 if (demo) {
                     valid = true;
@@ -212,19 +212,6 @@ export class CoreLoginSitePage implements OnInit {
         };
     }
 
-    /**
-     * Get the demo data for a certain "name" if it is a demo site.
-     *
-     * @param name Name of the site to check.
-     * @return Site data if it's a demo site, undefined otherwise.
-     */
-    getDemoSiteData(name: string): CoreSitesDemoSiteData {
-        const demoSites = CoreConfigConstants.demo_sites;
-        if (typeof demoSites != 'undefined' && typeof demoSites[name] != 'undefined') {
-            return demoSites[name];
-        }
-    }
-
     /**
      * Show a help modal.
      */
@@ -361,7 +348,11 @@ export class CoreLoginSitePage implements OnInit {
         if (CoreLoginHelper.instance.isSSOLoginNeeded(response.code)) {
             // SSO. User needs to authenticate in a browser.
             CoreLoginHelper.instance.confirmAndOpenBrowserForSSOLogin(
-                response.siteUrl, response.code, response.service, response.config && response.config.launchurl);
+                response.siteUrl,
+                response.code,
+                response.service,
+                response.config?.launchurl,
+            );
         } else {
             const pageParams = { siteUrl: response.siteUrl, siteConfig: response.config };
             if (foundSite) {
@@ -382,7 +373,7 @@ export class CoreLoginSitePage implements OnInit {
      * @param url The URL the user was trying to connect to.
      * @param error Error to display.
      */
-    protected showLoginIssue(url: string, error: CoreError): void {
+    protected showLoginIssue(url: string | null, error: CoreError): void {
         let errorMessage = CoreDomUtils.instance.getErrorMessage(error);
 
         if (errorMessage == Translate.instance.instant('core.cannotconnecttrouble')) {
@@ -452,10 +443,12 @@ export class CoreLoginSitePage implements OnInit {
             this.enteredSiteUrl = {
                 url: search,
                 name: 'connect',
+                title: '',
+                location: '',
                 noProtocolUrl: CoreUrl.removeProtocol(search),
             };
         } else {
-            this.enteredSiteUrl = null;
+            this.enteredSiteUrl = undefined;
         }
 
         this.searchFunction(search.trim());
@@ -468,8 +461,10 @@ export class CoreLoginSitePage implements OnInit {
         // Show some instructions first.
         CoreDomUtils.instance.showAlertWithOptions({
             header: Translate.instance.instant('core.login.faqwhereisqrcode'),
-            message: Translate.instance.instant('core.login.faqwhereisqrcodeanswer',
-                { $image: CoreLoginHelperProvider.FAQ_QRCODE_IMAGE_HTML }),
+            message: Translate.instance.instant(
+                'core.login.faqwhereisqrcodeanswer',
+                { $image: CoreLoginHelperProvider.FAQ_QRCODE_IMAGE_HTML },
+            ),
             buttons: [
                 {
                     text: Translate.instance.instant('core.cancel'),
@@ -505,9 +500,9 @@ export class CoreLoginSitePage implements OnInit {
  * Extended data for UI implementation.
  */
 type CoreLoginSiteInfoExtended = CoreLoginSiteInfo & {
-    noProtocolUrl?: string; // Url wihtout protocol.
-    location?: string; // City + country.
-    title?: string; // Name + alias.
+    noProtocolUrl: string; // Url wihtout protocol.
+    location: string; // City + country.
+    title: string; // Name + alias.
 };
 
 type SiteFinderSettings = {
diff --git a/src/app/core/login/services/helper.ts b/src/app/core/login/services/helper.ts
index a4256866e..cd3f3dbdf 100644
--- a/src/app/core/login/services/helper.ts
+++ b/src/app/core/login/services/helper.ts
@@ -50,7 +50,7 @@ export class CoreLoginHelperProvider {
     protected logger: CoreLogger;
     protected isSSOConfirmShown = false;
     protected isOpenEditAlertShown = false;
-    protected pageToLoad: {page: string; params: Params; time: number}; // Page to load once main menu is opened.
+    protected pageToLoad?: {page: string; params: Params; time: number}; // Page to load once main menu is opened.
     protected isOpeningReconnect = false;
     waitingForBrowser = false;
 
@@ -208,7 +208,7 @@ export class CoreLoginHelperProvider {
         const categories: Record<number, AuthEmailSignupProfileFieldsCategory> = {};
 
         profileFields.forEach((field) => {
-            if (!field.signup) {
+            if (!field.signup || !field.categoryid) {
                 // Not a signup field, ignore it.
                 return;
             }
@@ -216,7 +216,7 @@ export class CoreLoginHelperProvider {
             if (!categories[field.categoryid]) {
                 categories[field.categoryid] = {
                     id: field.categoryid,
-                    name: field.categoryname,
+                    name: field.categoryname || '',
                     fields: [],
                 };
             }
@@ -233,8 +233,8 @@ export class CoreLoginHelperProvider {
      * @param config Site public config.
      * @return Disabled features.
      */
-    getDisabledFeatures(config: CoreSitePublicConfigResponse): string {
-        const disabledFeatures = config && config.tool_mobile_disabledfeatures;
+    getDisabledFeatures(config?: CoreSitePublicConfigResponse): string {
+        const disabledFeatures = config?.tool_mobile_disabledfeatures;
         if (!disabledFeatures) {
             return '';
         }
@@ -302,8 +302,8 @@ export class CoreLoginHelperProvider {
      * @param config Site public config.
      * @return Logo URL.
      */
-    getLogoUrl(config: CoreSitePublicConfigResponse): string {
-        return !CoreConfigConstants.forceLoginLogo && config ? (config.logourl || config.compactlogourl) : null;
+    getLogoUrl(config: CoreSitePublicConfigResponse): string | undefined {
+        return !CoreConfigConstants.forceLoginLogo && config ? (config.logourl || config.compactlogourl) : undefined;
     }
 
     /**
@@ -314,7 +314,7 @@ export class CoreLoginHelperProvider {
      */
     getLogoutLabel(site?: CoreSite): string {
         site = site || CoreSites.instance.getCurrentSite();
-        const config = <CoreSiteConfig> site.getStoredConfig();
+        const config = <CoreSiteConfig> site?.getStoredConfig();
 
         return 'core.mainmenu.' + (config && config.tool_mobile_forcelogout == '1' ? 'logout' : 'changesite');
     }
@@ -325,7 +325,7 @@ export class CoreLoginHelperProvider {
      * @param params Params.
      * @return OAuth ID.
      */
-    getOAuthIdFromParams(params: CoreUrlParams): number {
+    getOAuthIdFromParams(params: CoreUrlParams): number | undefined {
         return params && typeof params.oauthsso != 'undefined' ? Number(params.oauthsso) : undefined;
     }
 
@@ -338,15 +338,18 @@ export class CoreLoginHelperProvider {
     async getSitePolicy(siteId?: string): Promise<string> {
         const site = await CoreSites.instance.getSite(siteId);
 
-        let sitePolicy: string;
+        let sitePolicy: string | undefined;
 
         try {
             // Try to get the latest config, maybe the site policy was just added or has changed.
             sitePolicy = <string> await site.getConfig('sitepolicy', true);
         } catch (error) {
             // Cannot get config, try to get the site policy using auth_email_get_signup_settings.
-            const settings = <AuthEmailSignupSettings> await CoreWS.instance.callAjax('auth_email_get_signup_settings', {},
-                { siteUrl: site.getURL() });
+            const settings = <AuthEmailSignupSettings> await CoreWS.instance.callAjax(
+                'auth_email_get_signup_settings',
+                {},
+                { siteUrl: site.getURL() },
+            );
 
             sitePolicy = settings.sitepolicy;
         }
@@ -374,7 +377,10 @@ export class CoreLoginHelperProvider {
      * @param disabledFeatures List of disabled features already treated. If not provided it will be calculated.
      * @return Valid identity providers.
      */
-    getValidIdentityProviders(siteConfig: CoreSitePublicConfigResponse, disabledFeatures?: string): CoreSiteIdentityProvider[] {
+    getValidIdentityProviders(siteConfig?: CoreSitePublicConfigResponse, disabledFeatures?: string): CoreSiteIdentityProvider[] {
+        if (!siteConfig) {
+            return [];
+        }
         if (this.isFeatureDisabled('NoDelegate_IdentityProviders', siteConfig, disabledFeatures)) {
             // Identity providers are disabled, return an empty list.
             return [];
@@ -460,8 +466,8 @@ export class CoreLoginHelperProvider {
      * @return Whether there are several fixed URLs.
      */
     hasSeveralFixedSites(): boolean {
-        return CoreConfigConstants.siteurl && Array.isArray(CoreConfigConstants.siteurl) &&
-            CoreConfigConstants.siteurl.length > 1;
+        return !!(CoreConfigConstants.siteurl && Array.isArray(CoreConfigConstants.siteurl) &&
+            CoreConfigConstants.siteurl.length > 1);
     }
 
     /**
@@ -923,8 +929,14 @@ export class CoreLoginHelperProvider {
                     try {
                         this.waitingForBrowser = true;
 
-                        this.openBrowserForSSOLogin(result.siteUrl, result.code, result.service, result.config?.launchurl,
-                            data.pageName, data.params);
+                        this.openBrowserForSSOLogin(
+                            result.siteUrl,
+                            result.code,
+                            result.service,
+                            result.config?.launchurl,
+                            data.pageName,
+                            data.params,
+                        );
                     } catch (error) {
                         // User cancelled, logout him.
                         CoreSites.instance.logout();
@@ -956,8 +968,13 @@ export class CoreLoginHelperProvider {
                                 this.waitingForBrowser = true;
                                 CoreSites.instance.unsetCurrentSite(); // Unset current site to make authentication work fine.
 
-                                this.openBrowserForOAuthLogin(siteUrl, providerToUse, result.config.launchurl, data.pageName,
-                                        data.params);
+                                this.openBrowserForOAuthLogin(
+                                    siteUrl,
+                                    providerToUse,
+                                    result.config?.launchurl,
+                                    data.pageName,
+                                    data.params,
+                                );
                             } catch (error) {
                                 // User cancelled, logout him.
                                 CoreSites.instance.logout();
@@ -1067,10 +1084,13 @@ export class CoreLoginHelperProvider {
 
             try {
                 const result = <ResendConfirmationEmailResult> await CoreWS.instance.callAjax(
-                    'core_auth_resend_confirmation_email', data, preSets);
+                    'core_auth_resend_confirmation_email',
+                    data,
+                    preSets,
+                );
 
                 if (!result.status) {
-                    throw new CoreWSError(result.warnings[0]);
+                    throw new CoreWSError(result.warnings?.[0]);
                 }
 
                 const message = Translate.instance.instant('core.login.emailconfirmsentsuccess');
@@ -1096,6 +1116,8 @@ export class CoreLoginHelperProvider {
         try {
             // This call will always fail because we aren't sending parameters.
             await CoreWS.instance.callAjax('core_auth_resend_confirmation_email', {}, { siteUrl });
+
+            return true; // We should never reach here.
         } catch (error) {
             // If the WS responds with an invalid parameter error it means the WS is avaiable.
             return error?.errorcode === 'invalidparameter';
@@ -1134,13 +1156,13 @@ export class CoreLoginHelperProvider {
      */
     treatUserTokenError(siteUrl: string, error: CoreWSError, username?: string, password?: string): void {
         if (error.errorcode == 'forcepasswordchangenotice') {
-            this.openChangePassword(siteUrl, CoreTextUtils.instance.getErrorMessageFromError(error));
+            this.openChangePassword(siteUrl, CoreTextUtils.instance.getErrorMessageFromError(error)!);
         } else if (error.errorcode == 'usernotconfirmed') {
             this.showNotConfirmedModal(siteUrl, undefined, username, password);
         } else if (error.errorcode == 'connecttomoodleapp') {
-            this.showMoodleAppNoticeModal(CoreTextUtils.instance.getErrorMessageFromError(error));
+            this.showMoodleAppNoticeModal(CoreTextUtils.instance.getErrorMessageFromError(error)!);
         } else if (error.errorcode == 'connecttoworkplaceapp') {
-            this.showWorkplaceNoticeModal(CoreTextUtils.instance.getErrorMessageFromError(error));
+            this.showWorkplaceNoticeModal(CoreTextUtils.instance.getErrorMessageFromError(error)!);
         } else {
             CoreDomUtils.instance.showErrorModal(error);
         }
diff --git a/src/app/directives/format-text.ts b/src/app/directives/format-text.ts
index e4c74ebaa..7c679563e 100644
--- a/src/app/directives/format-text.ts
+++ b/src/app/directives/format-text.ts
@@ -15,7 +15,7 @@
 import { Directive, ElementRef, Input, Output, EventEmitter, OnChanges, SimpleChange, Optional } from '@angular/core';
 import { NavController, IonContent } from '@ionic/angular';
 
-import { CoreEventLoadingChangedData, CoreEvents, CoreEventsProvider } from '@services/events';
+import { CoreEventLoadingChangedData, CoreEventObserver, CoreEvents, CoreEventsProvider } from '@services/events';
 import { CoreSites } from '@services/sites';
 import { CoreDomUtils } from '@services/utils/dom';
 import { CoreIframeUtils, CoreIframeUtilsProvider } from '@services/utils/iframe';
@@ -38,7 +38,7 @@ import { Translate } from '@singletons/core.singletons';
 })
 export class CoreFormatTextDirective implements OnChanges {
 
-    @Input() text: string; // The text to format.
+    @Input() text?: string; // The text to format.
     @Input() siteId?: string; // Site ID to use.
     @Input() component?: string; // Component for CoreExternalContentDirective.
     @Input() componentId?: string | number; // Component ID to use in conjunction with the component.
@@ -56,11 +56,11 @@ export class CoreFormatTextDirective implements OnChanges {
     @Input() contextInstanceId?: number; // The instance ID related to the context.
     @Input() courseId?: number; // Course ID the text belongs to. It can be used to improve performance with filters.
     @Input() wsNotFiltered?: boolean | string; // If true it means the WS didn't filter the text for some reason.
-    @Output() afterRender?: EventEmitter<void>; // Called when the data is rendered.
+    @Output() afterRender: EventEmitter<void>; // Called when the data is rendered.
 
     protected element: HTMLElement;
-    protected showMoreDisplayed: boolean;
-    protected loadingChangedListener;
+    protected showMoreDisplayed = false;
+    protected loadingChangedListener?: CoreEventObserver;
 
     constructor(
         element: ElementRef,
@@ -116,9 +116,9 @@ export class CoreFormatTextDirective implements OnChanges {
         const container = document.createElement('span');
         const originalWidth = img.attributes.getNamedItem('width');
 
-        const forcedWidth = parseInt(originalWidth && originalWidth.value);
+        const forcedWidth = Number(originalWidth?.value);
         if (!isNaN(forcedWidth)) {
-            if (originalWidth.value.indexOf('%') < 0) {
+            if (originalWidth!.value.indexOf('%') < 0) {
                 img.style.width = forcedWidth  + 'px';
             } else {
                 img.style.width = forcedWidth  + '%';
@@ -160,7 +160,7 @@ export class CoreFormatTextDirective implements OnChanges {
                 return;
             }
 
-            let imgWidth = parseInt(img.getAttribute('width'));
+            let imgWidth = Number(img.getAttribute('width'));
             if (!imgWidth) {
                 // No width attribute, use real size.
                 imgWidth = img.naturalWidth;
@@ -185,7 +185,7 @@ export class CoreFormatTextDirective implements OnChanges {
                 CoreDomUtils.instance.viewImage(imgSrc, img.getAttribute('alt'), this.component, this.componentId, true);
             });
 
-            img.parentNode.appendChild(anchor);
+            img.parentNode?.appendChild(anchor);
         });
     }
 
@@ -194,10 +194,13 @@ export class CoreFormatTextDirective implements OnChanges {
      */
     protected calculateHeight(): void {
         // @todo: Work on calculate this height better.
+        if (!this.maxHeight) {
+            return;
+        }
 
         // Remove max-height (if any) to calculate the real height.
         const initialMaxHeight = this.element.style.maxHeight;
-        this.element.style.maxHeight = null;
+        this.element.style.maxHeight = '';
 
         const height = this.getElementHeight(this.element);
 
@@ -245,6 +248,9 @@ export class CoreFormatTextDirective implements OnChanges {
             // Ignore it if the event was prevented by some other listener.
             return;
         }
+        if (!this.text) {
+            return;
+        }
 
         const expandInFullview = CoreUtils.instance.isTrueOrOne(this.fullOnClick) || false;
 
@@ -265,14 +271,18 @@ export class CoreFormatTextDirective implements OnChanges {
             // Open a new state with the contents.
             const filter = typeof this.filter != 'undefined' ? CoreUtils.instance.isTrueOrOne(this.filter) : undefined;
 
-            CoreTextUtils.instance.viewText(this.fullTitle || Translate.instance.instant('core.description'), this.text, {
-                component: this.component,
-                componentId: this.componentId,
-                filter: filter,
-                contextLevel: this.contextLevel,
-                instanceId: this.contextInstanceId,
-                courseId: this.courseId,
-            });
+            CoreTextUtils.instance.viewText(
+                this.fullTitle || Translate.instance.instant('core.description'),
+                this.text,
+                {
+                    component: this.component,
+                    componentId: this.componentId,
+                    filter: filter,
+                    contextLevel: this.contextLevel,
+                    instanceId: this.contextInstanceId,
+                    courseId: this.courseId,
+                },
+            );
         }
     }
 
@@ -357,29 +367,17 @@ export class CoreFormatTextDirective implements OnChanges {
      * @return Promise resolved with a div element containing the code.
      */
     protected async formatContents(): Promise<FormatContentsResult> {
-
-        const result: FormatContentsResult = {
-            div: null,
-            filters: [],
-            options: {},
-            siteId: this.siteId,
-        };
-
         // Retrieve the site since it might be needed later.
         const site = await CoreUtils.instance.ignoreErrors(CoreSites.instance.getSite(this.siteId));
 
-        if (site) {
-            result.siteId = site.getId();
-        }
-
-        if (this.contextLevel == 'course' && this.contextInstanceId <= 0) {
+        if (site && this.contextLevel == 'course' && this.contextInstanceId !== undefined && this.contextInstanceId <= 0) {
             this.contextInstanceId = site.getSiteHomeId();
         }
 
         const filter = typeof this.filter == 'undefined' ?
             !!(this.contextLevel && typeof this.contextInstanceId != 'undefined') : CoreUtils.instance.isTrueOrOne(this.filter);
 
-        result.options = {
+        const options = {
             clean: CoreUtils.instance.isTrueOrOne(this.clean),
             singleLine: CoreUtils.instance.isTrueOrOne(this.singleLine),
             highlight: this.highlight,
@@ -391,10 +389,10 @@ export class CoreFormatTextDirective implements OnChanges {
 
         if (filter) {
             // @todo
-            formatted = this.text;
+            formatted = this.text!;
         } else {
             // @todo
-            formatted = this.text;
+            formatted = this.text!;
         }
 
         formatted = this.treatWindowOpen(formatted);
@@ -405,9 +403,12 @@ export class CoreFormatTextDirective implements OnChanges {
 
         this.treatHTMLElements(div, site);
 
-        result.div = div;
-
-        return result;
+        return {
+            div,
+            filters: [],
+            options,
+            siteId: site?.getId(),
+        };
     }
 
     /**
@@ -418,7 +419,7 @@ export class CoreFormatTextDirective implements OnChanges {
      * @return Promise resolved when done.
      */
     protected async treatHTMLElements(div: HTMLElement, site?: CoreSite): Promise<void> {
-        const canTreatVimeo = site && site.isVersionGreaterEqualThan(['3.3.4', '3.4']);
+        const canTreatVimeo = site?.isVersionGreaterEqualThan(['3.3.4', '3.4']) || false;
         const navCtrl = this.navCtrl; // @todo this.svComponent ? this.svComponent.getMasterNav() : this.navCtrl;
 
         const images = Array.from(div.querySelectorAll('img'));
@@ -537,7 +538,8 @@ export class CoreFormatTextDirective implements OnChanges {
 
         if (!width) {
             // All elements inside are floating or inline. Change display mode to allow calculate the width.
-            const parentWidth = CoreDomUtils.instance.getElementWidth(element.parentElement, true, false, false, true);
+            const parentWidth = element.parentElement ?
+                CoreDomUtils.instance.getElementWidth(element.parentElement, true, false, false, true) : 0;
             const previousDisplay = getComputedStyle(element, null).display;
 
             element.style.display = 'inline-block';
@@ -578,7 +580,7 @@ export class CoreFormatTextDirective implements OnChanges {
         this.element.classList.remove('core-expand-in-fullview');
         this.element.classList.remove('core-text-formatted');
         this.element.classList.remove('core-shortened');
-        this.element.style.maxHeight = null;
+        this.element.style.maxHeight = '';
         this.showMoreDisplayed = false;
     }
 
@@ -595,7 +597,7 @@ export class CoreFormatTextDirective implements OnChanges {
         const tracks = Array.from(element.querySelectorAll('track'));
 
         sources.forEach((source) => {
-            source.setAttribute('target-src', source.getAttribute('src'));
+            source.setAttribute('target-src', source.getAttribute('src') || '');
             source.removeAttribute('src');
             this.addExternalContent(source);
         });
@@ -618,8 +620,12 @@ export class CoreFormatTextDirective implements OnChanges {
      * @param canTreatVimeo Whether Vimeo videos can be treated in the site.
      * @param navCtrl NavController to use.
      */
-    protected async treatIframe(iframe: HTMLIFrameElement, site: CoreSite, canTreatVimeo: boolean, navCtrl: NavController):
-            Promise<void> {
+    protected async treatIframe(
+        iframe: HTMLIFrameElement,
+        site: CoreSite | undefined,
+        canTreatVimeo: boolean,
+        navCtrl: NavController,
+    ): Promise<void> {
         const src = iframe.src;
         const currentSite = CoreSites.instance.getCurrentSite();
 
@@ -636,7 +642,7 @@ export class CoreFormatTextDirective implements OnChanges {
             return;
         }
 
-        if (src && canTreatVimeo) {
+        if (site && src && canTreatVimeo) {
             // Check if it's a Vimeo video. If it is, use the wsplayer script instead to make restricted videos work.
             const matches = iframe.src.match(/https?:\/\/player\.vimeo\.com\/video\/([0-9]+)/);
             if (matches && matches[1]) {
@@ -679,7 +685,7 @@ export class CoreFormatTextDirective implements OnChanges {
                 }
 
                 // Do the iframe responsive.
-                if (iframe.parentElement.classList.contains('embed-responsive')) {
+                if (iframe.parentElement?.classList.contains('embed-responsive')) {
                     iframe.addEventListener('load', () => {
                         if (iframe.contentDocument) {
                             const css = document.createElement('style');
@@ -723,5 +729,5 @@ type FormatContentsResult = {
     div: HTMLElement;
     filters: any[];
     options: any;
-    siteId: string;
+    siteId?: string;
 };
diff --git a/src/app/directives/supress-events.ts b/src/app/directives/supress-events.ts
index 0b3c363a2..401578d8b 100644
--- a/src/app/directives/supress-events.ts
+++ b/src/app/directives/supress-events.ts
@@ -38,7 +38,7 @@ import { Directive, ElementRef, OnInit, Input, Output, EventEmitter } from '@ang
 })
 export class CoreSupressEventsDirective implements OnInit {
 
-    @Input('core-suppress-events') suppressEvents: string | string[];
+    @Input('core-suppress-events') suppressEvents?: string | string[];
     @Output() onClick = new EventEmitter(); // eslint-disable-line @angular-eslint/no-output-on-prefix
 
     protected element: HTMLElement;
diff --git a/src/app/services/app.ts b/src/app/services/app.ts
index 1b3bd700a..5f983adcd 100644
--- a/src/app/services/app.ts
+++ b/src/app/services/app.ts
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 import { Injectable, NgZone, ApplicationRef } from '@angular/core';
+import { Params } from '@angular/router';
 import { Connection } from '@ionic-native/network/ngx';
 
 import { CoreDB } from '@services/db';
@@ -224,7 +225,7 @@ export class CoreAppProvider {
      * @param  storesConfig Config params to send the user to the right place.
      * @return Store URL.
      */
-    getAppStoreUrl(storesConfig: CoreStoreConfig): string | null {
+    getAppStoreUrl(storesConfig: CoreStoreConfig): string | undefined {
         if (this.isMac() && storesConfig.mac) {
             return 'itms-apps://itunes.apple.com/app/' + storesConfig.mac;
         }
@@ -253,7 +254,7 @@ export class CoreAppProvider {
             return storesConfig.mobile;
         }
 
-        return storesConfig.default || null;
+        return storesConfig.default;
     }
 
     /**
@@ -563,11 +564,11 @@ export class CoreAppProvider {
      *
      * @return Object with siteid, state, params and timemodified.
      */
-    getRedirect<Params extends Record<string, unknown> = Record<string, unknown>>(): CoreRedirectData<Params> {
+    getRedirect(): CoreRedirectData {
         if (localStorage?.getItem) {
             try {
                 const paramsJson = localStorage.getItem('CoreRedirectParams');
-                const data: CoreRedirectData<Params> = {
+                const data: CoreRedirectData = {
                     siteId: localStorage.getItem('CoreRedirectSiteId') || undefined,
                     page: localStorage.getItem('CoreRedirectState')  || undefined,
                     timemodified: parseInt(localStorage.getItem('CoreRedirectTime') || '0', 10),
@@ -593,7 +594,7 @@ export class CoreAppProvider {
      * @param page Page to go.
      * @param params Page params.
      */
-    storeRedirect(siteId: string, page: string, params: Record<string, unknown>): void {
+    storeRedirect(siteId: string, page: string, params: Params): void {
         if (localStorage && localStorage.setItem) {
             try {
                 localStorage.setItem('CoreRedirectSiteId', siteId);
@@ -697,7 +698,7 @@ export class CoreApp extends makeSingleton(CoreAppProvider) {}
 /**
  * Data stored for a redirect to another page/site.
  */
-export type CoreRedirectData<Params extends Record<string, unknown>> = {
+export type CoreRedirectData = {
     /**
      * ID of the site to load.
      */
diff --git a/src/app/services/cron.ts b/src/app/services/cron.ts
index 53c23b38a..a4e6cdf38 100644
--- a/src/app/services/cron.ts
+++ b/src/app/services/cron.ts
@@ -97,18 +97,17 @@ export class CoreCronDelegate {
      * @param siteId Site ID. If not defined, all sites.
      * @return Promise resolved if handler is executed successfully, rejected otherwise.
      */
-    protected checkAndExecuteHandler(name: string, force?: boolean, siteId?: string): Promise<void> {
+    protected async checkAndExecuteHandler(name: string, force?: boolean, siteId?: string): Promise<void> {
         if (!this.handlers[name] || !this.handlers[name].execute) {
             // Invalid handler.
             const message = `Cannot execute handler because is invalid: ${name}`;
             this.logger.debug(message);
 
-            return Promise.reject(new CoreError(message));
+            throw new CoreError(message);
         }
 
         const usesNetwork = this.handlerUsesNetwork(name);
         const isSync = !force && this.isHandlerSync(name);
-        let promise;
 
         if (usesNetwork && !CoreApp.instance.isOnline()) {
             // Offline, stop executing.
@@ -116,47 +115,46 @@ export class CoreCronDelegate {
             this.logger.debug(message);
             this.stopHandler(name);
 
-            return Promise.reject(new CoreError(message));
+            throw new CoreError(message);
         }
 
         if (isSync) {
             // Check network connection.
-            promise = CoreConfig.instance.get(CoreConstants.SETTINGS_SYNC_ONLY_ON_WIFI, false)
-                .then((syncOnlyOnWifi) => !syncOnlyOnWifi || CoreApp.instance.isWifi());
-        } else {
-            promise = Promise.resolve(true);
-        }
+            const syncOnlyOnWifi = await CoreConfig.instance.get(CoreConstants.SETTINGS_SYNC_ONLY_ON_WIFI, false);
 
-        return promise.then((execute: boolean) => {
-            if (!execute) {
+            if (syncOnlyOnWifi && !CoreApp.instance.isWifi()) {
                 // Cannot execute in this network connection, retry soon.
                 const message = `Cannot execute handler because device is using limited connection: ${name}`;
                 this.logger.debug(message);
                 this.scheduleNextExecution(name, CoreCronDelegate.MIN_INTERVAL);
 
-                return Promise.reject(new CoreError(message));
+                throw new CoreError(message);
             }
+        }
+
+        // Add the execution to the queue.
+        this.queuePromise = CoreUtils.instance.ignoreErrors(this.queuePromise).then(async () => {
+            try {
+                await this.executeHandler(name, force, siteId);
 
-            // Add the execution to the queue.
-            this.queuePromise = this.queuePromise.catch(() => {
-                // Ignore errors in previous handlers.
-            }).then(() => this.executeHandler(name, force, siteId).then(() => {
                 this.logger.debug(`Execution of handler '${name}' was a success.`);
 
-                return this.setHandlerLastExecutionTime(name, Date.now()).then(() => {
-                    this.scheduleNextExecution(name);
-                });
-            }, (error) => {
+                await CoreUtils.instance.ignoreErrors(this.setHandlerLastExecutionTime(name, Date.now()));
+
+                this.scheduleNextExecution(name);
+
+                return;
+            } catch (error) {
                 // Handler call failed. Retry soon.
                 const message = `Execution of handler '${name}' failed.`;
                 this.logger.error(message, error);
                 this.scheduleNextExecution(name, CoreCronDelegate.MIN_INTERVAL);
 
-                return Promise.reject(new CoreError(message));
-            }));
-
-            return this.queuePromise;
+                throw new CoreError(message);
+            }
         });
+
+        return this.queuePromise;
     }
 
     /**
@@ -172,7 +170,7 @@ export class CoreCronDelegate {
             this.logger.debug('Executing handler: ' + name);
 
             // Wrap the call in Promise.resolve to make sure it's a promise.
-            Promise.resolve(this.handlers[name].execute(siteId, force)).then(resolve).catch(reject).finally(() => {
+            Promise.resolve(this.handlers[name].execute!(siteId, force)).then(resolve).catch(reject).finally(() => {
                 clearTimeout(cancelTimeout);
             });
 
@@ -192,7 +190,7 @@ export class CoreCronDelegate {
      * @return Promise resolved if all handlers are executed successfully, rejected otherwise.
      */
     async forceSyncExecution(siteId?: string): Promise<void> {
-        const promises = [];
+        const promises: Promise<void>[] = [];
 
         for (const name in this.handlers) {
             if (this.isHandlerManualSync(name)) {
@@ -208,11 +206,11 @@ export class CoreCronDelegate {
      * Force execution of a cron tasks without waiting for the scheduled time.
      * Please notice that some tasks may not be executed depending on the network connection and sync settings.
      *
-     * @param name If provided, the name of the handler.
+     * @param name Name of the handler.
      * @param siteId Site ID. If not defined, all sites.
      * @return Promise resolved if handler has been executed successfully, rejected otherwise.
      */
-    forceCronHandlerExecution(name?: string, siteId?: string): Promise<void> {
+    forceCronHandlerExecution(name: string, siteId?: string): Promise<void> {
         const handler = this.handlers[name];
 
         // Mark the handler as running (it might be running already).
@@ -240,7 +238,7 @@ export class CoreCronDelegate {
 
         // Don't allow intervals lower than the minimum.
         const minInterval = CoreApp.instance.isDesktop() ? CoreCronDelegate.DESKTOP_MIN_INTERVAL : CoreCronDelegate.MIN_INTERVAL;
-        const handlerInterval = this.handlers[name].getInterval();
+        const handlerInterval = this.handlers[name].getInterval!();
 
         if (!handlerInterval) {
             return CoreCronDelegate.DEFAULT_INTERVAL;
@@ -288,12 +286,12 @@ export class CoreCronDelegate {
      * @return True if handler uses network or not defined, false otherwise.
      */
     protected handlerUsesNetwork(name: string): boolean {
-        if (!this.handlers[name] || !this.handlers[name].usesNetwork) {
+        if (!this.handlers[name] || this.handlers[name].usesNetwork) {
             // Invalid, return default.
             return true;
         }
 
-        return this.handlers[name].usesNetwork();
+        return this.handlers[name].usesNetwork!();
     }
 
     /**
@@ -338,7 +336,7 @@ export class CoreCronDelegate {
             return this.isHandlerSync(name);
         }
 
-        return this.handlers[name].canManualSync();
+        return this.handlers[name].canManualSync!();
     }
 
     /**
@@ -353,7 +351,7 @@ export class CoreCronDelegate {
             return true;
         }
 
-        return this.handlers[name].isSync();
+        return this.handlers[name].isSync!();
     }
 
     /**
@@ -385,10 +383,10 @@ export class CoreCronDelegate {
      * Schedule a next execution for a handler.
      *
      * @param name Name of the handler.
-     * @param time Time to the next execution. If not supplied it will be calculated using the last execution and
-     *             the handler's interval. This param should be used only if it's really necessary.
+     * @param timeToNextExecution Time (in milliseconds). If not supplied it will be calculated.
+     * @return Promise resolved when done.
      */
-    protected scheduleNextExecution(name: string, time?: number): void {
+    protected async scheduleNextExecution(name: string, timeToNextExecution?: number): Promise<void> {
         if (!this.handlers[name]) {
             // Invalid handler.
             return;
@@ -398,33 +396,24 @@ export class CoreCronDelegate {
             return;
         }
 
-        let promise;
-
-        if (time) {
-            promise = Promise.resolve(time);
-        } else {
+        if (!timeToNextExecution) {
             // Get last execution time to check when do we need to execute it.
-            promise = this.getHandlerLastExecutionTime(name).then((lastExecution) => {
-                const interval = this.getHandlerInterval(name);
-                const nextExecution = lastExecution + interval;
+            const lastExecution = await this.getHandlerLastExecutionTime(name);
 
-                return nextExecution - Date.now();
-            });
+            const interval = this.getHandlerInterval(name);
+
+            timeToNextExecution = lastExecution + interval - Date.now();
         }
 
-        promise.then((nextExecution) => {
-            this.logger.debug(`Scheduling next execution of handler '${name}' in '${nextExecution}' ms`);
-            if (nextExecution < 0) {
-                nextExecution = 0; // Big negative numbers aren't executed immediately.
-            }
+        this.logger.debug(`Scheduling next execution of handler '${name}' in '${timeToNextExecution}' ms`);
+        if (timeToNextExecution < 0) {
+            timeToNextExecution = 0; // Big negative numbers aren't executed immediately.
+        }
 
-            this.handlers[name].timeout = window.setTimeout(() => {
-                delete this.handlers[name].timeout;
-                this.checkAndExecuteHandler(name).catch(() => {
-                    // Ignore errors.
-                });
-            }, nextExecution);
-        });
+        this.handlers[name].timeout = window.setTimeout(() => {
+            delete this.handlers[name].timeout;
+            CoreUtils.instance.ignoreErrors(this.checkAndExecuteHandler(name));
+        }, timeToNextExecution);
     }
 
     /**
diff --git a/src/app/services/file-helper.ts b/src/app/services/file-helper.ts
index 31ac0aa8c..ae7842ebd 100644
--- a/src/app/services/file-helper.ts
+++ b/src/app/services/file-helper.ts
@@ -44,11 +44,17 @@ export class CoreFileHelperProvider {
      * @param siteId The site ID. If not defined, current site.
      * @return Resolved on success.
      */
-    async downloadAndOpenFile(file: CoreWSExternalFile, component: string, componentId: string | number, state?: string,
-            onProgress?: CoreFileHelperOnProgress, siteId?: string): Promise<void> {
+    async downloadAndOpenFile(
+        file: CoreWSExternalFile,
+        component: string,
+        componentId: string | number,
+        state?: string,
+        onProgress?: CoreFileHelperOnProgress,
+        siteId?: string,
+    ): Promise<void> {
         siteId = siteId || CoreSites.instance.getCurrentSiteId();
 
-        const fileUrl = this.getFileUrl(file);
+        const fileUrl = file.fileurl;
         const timemodified = this.getFileTimemodified(file);
 
         if (!this.isOpenableInApp(file)) {
@@ -111,70 +117,76 @@ export class CoreFileHelperProvider {
      * @param siteId The site ID. If not defined, current site.
      * @return Resolved with the URL to use on success.
      */
-    protected downloadFileIfNeeded(file: CoreWSExternalFile, fileUrl: string, component?: string, componentId?: string | number,
-            timemodified?: number, state?: string, onProgress?: CoreFileHelperOnProgress, siteId?: string): Promise<string> {
+    protected async downloadFileIfNeeded(
+        file: CoreWSExternalFile,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified?: number,
+        state?: string,
+        onProgress?: CoreFileHelperOnProgress,
+        siteId?: string,
+    ): Promise<string> {
         siteId = siteId || CoreSites.instance.getCurrentSiteId();
 
-        return CoreSites.instance.getSite(siteId).then((site) => site.checkAndFixPluginfileURL(fileUrl)).then((fixedUrl) => {
-            if (CoreFile.instance.isAvailable()) {
-                let promise;
-                if (state) {
-                    promise = Promise.resolve(state);
-                } else {
-                    // Calculate the state.
-                    promise = CoreFilepool.instance.getFileStateByUrl(siteId, fileUrl, timemodified);
+        const site = await CoreSites.instance.getSite(siteId);
+        const fixedUrl = await site.checkAndFixPluginfileURL(fileUrl);
+
+        if (!CoreFile.instance.isAvailable()) {
+            // Use the online URL.
+            return fixedUrl;
+        }
+
+        if (!state) {
+            // Calculate the state.
+            state = await CoreFilepool.instance.getFileStateByUrl(siteId, fileUrl, timemodified);
+        }
+
+        // The file system is available.
+        const isWifi = CoreApp.instance.isWifi();
+        const isOnline = CoreApp.instance.isOnline();
+
+        if (state == CoreConstants.DOWNLOADED) {
+            // File is downloaded, get the local file URL.
+            return CoreFilepool.instance.getUrlByUrl(siteId, fileUrl, component, componentId, timemodified, false, false, file);
+        } else {
+            if (!isOnline && !this.isStateDownloaded(state)) {
+                // Not downloaded and user is offline, reject.
+                throw new CoreError(Translate.instance.instant('core.networkerrormsg'));
+            }
+
+            if (onProgress) {
+                // This call can take a while. Send a fake event to notify that we're doing some calculations.
+                onProgress({ calculating: true });
+            }
+
+            try {
+                await CoreFilepool.instance.shouldDownloadBeforeOpen(fixedUrl, file.filesize || 0);
+            } catch (error) {
+                // Start the download if in wifi, but return the URL right away so the file is opened.
+                if (isWifi) {
+                    this.downloadFile(fileUrl, component, componentId, timemodified, onProgress, file, siteId);
                 }
 
-                return promise.then((state) => {
-                    // The file system is available.
-                    const isWifi = CoreApp.instance.isWifi();
-                    const isOnline = CoreApp.instance.isOnline();
+                if (!this.isStateDownloaded(state) || isOnline) {
+                    // Not downloaded or online, return the online URL.
+                    return fixedUrl;
+                } else {
+                    // Outdated but offline, so we return the local URL.
+                    return CoreFilepool.instance.getUrlByUrl(
+                        siteId, fileUrl, component, componentId, timemodified, false, false, file);
+                }
+            }
 
-                    if (state == CoreConstants.DOWNLOADED) {
-                        // File is downloaded, get the local file URL.
-                        return CoreFilepool.instance.getUrlByUrl(
-                            siteId, fileUrl, component, componentId, timemodified, false, false, file);
-                    } else {
-                        if (!isOnline && !this.isStateDownloaded(state)) {
-                            // Not downloaded and user is offline, reject.
-                            return Promise.reject(new CoreError(Translate.instance.instant('core.networkerrormsg')));
-                        }
-
-                        if (onProgress) {
-                            // This call can take a while. Send a fake event to notify that we're doing some calculations.
-                            onProgress({ calculating: true });
-                        }
-
-                        return CoreFilepool.instance.shouldDownloadBeforeOpen(fixedUrl, file.filesize).then(() => {
-                            if (state == CoreConstants.DOWNLOADING) {
-                                // It's already downloading, stop.
-                                return;
-                            }
-
-                            // Download and then return the local URL.
-                            return this.downloadFile(fileUrl, component, componentId, timemodified, onProgress, file, siteId);
-                        }, () => {
-                            // Start the download if in wifi, but return the URL right away so the file is opened.
-                            if (isWifi) {
-                                this.downloadFile(fileUrl, component, componentId, timemodified, onProgress, file, siteId);
-                            }
-
-                            if (!this.isStateDownloaded(state) || isOnline) {
-                                // Not downloaded or online, return the online URL.
-                                return fixedUrl;
-                            } else {
-                                // Outdated but offline, so we return the local URL.
-                                return CoreFilepool.instance.getUrlByUrl(
-                                    siteId, fileUrl, component, componentId, timemodified, false, false, file);
-                            }
-                        });
-                    }
-                });
-            } else {
-                // Use the online URL.
+            // Download the file first.
+            if (state == CoreConstants.DOWNLOADING) {
+                // It's already downloading, stop.
                 return fixedUrl;
             }
-        });
+
+            // Download and then return the local URL.
+            return this.downloadFile(fileUrl, component, componentId, timemodified, onProgress, file, siteId);
+        }
     }
 
     /**
@@ -189,29 +201,37 @@ export class CoreFileHelperProvider {
      * @param siteId The site ID. If not defined, current site.
      * @return Resolved with internal URL on success, rejected otherwise.
      */
-    downloadFile(fileUrl: string, component?: string, componentId?: string | number, timemodified?: number,
-        onProgress?: (event: ProgressEvent) => void, file?: CoreWSExternalFile, siteId?: string): Promise<string> {
+    async downloadFile(
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified?: number,
+        onProgress?: (event: ProgressEvent) => void,
+        file?: CoreWSExternalFile,
+        siteId?: string,
+    ): Promise<string> {
         siteId = siteId || CoreSites.instance.getCurrentSiteId();
 
         // Get the site and check if it can download files.
-        return CoreSites.instance.getSite(siteId).then((site) => {
-            if (!site.canDownloadFiles()) {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.cannotdownloadfiles')));
+        const site = await CoreSites.instance.getSite(siteId);
+
+        if (!site.canDownloadFiles()) {
+            throw new CoreError(Translate.instance.instant('core.cannotdownloadfiles'));
+        }
+
+        try {
+            return await CoreFilepool.instance.downloadUrl(siteId, fileUrl, false, component, componentId, timemodified,
+                onProgress, undefined, file);
+        } catch (error) {
+            // Download failed, check the state again to see if the file was downloaded before.
+            const state = await CoreFilepool.instance.getFileStateByUrl(siteId, fileUrl, timemodified);
+
+            if (this.isStateDownloaded(state)) {
+                return CoreFilepool.instance.getInternalUrlByUrl(siteId, fileUrl);
+            } else {
+                throw error;
             }
-
-            return CoreFilepool.instance.downloadUrl(siteId, fileUrl, false, component, componentId,
-                timemodified, onProgress, undefined, file).catch((error) =>
-
-                // Download failed, check the state again to see if the file was downloaded before.
-                CoreFilepool.instance.getFileStateByUrl(siteId, fileUrl, timemodified).then((state) => {
-                    if (this.isStateDownloaded(state)) {
-                        return CoreFilepool.instance.getInternalUrlByUrl(siteId, fileUrl);
-                    } else {
-                        return Promise.reject(error);
-                    }
-                }),
-            );
-        });
+        }
     }
 
     /**
@@ -220,7 +240,7 @@ export class CoreFileHelperProvider {
      * @param file The file.
      * @deprecated since 3.9.5. Get directly the fileurl instead.
      */
-    getFileUrl(file: CoreWSExternalFile): string {
+    getFileUrl(file: CoreWSExternalFile): string | undefined {
         return file.fileurl;
     }
 
@@ -337,11 +357,15 @@ export class CoreFileHelperProvider {
      * @return bool.
      */
     isOpenableInApp(file: {filename?: string; name?: string}): boolean {
-        const re = /(?:\.([^.]+))?$/;
+        const regex = /(?:\.([^.]+))?$/;
+        const regexResult = regex.exec(file.filename || file.name || '');
 
-        const ext = re.exec(file.filename || file.name)[1];
+        if (!regexResult || !regexResult[1]) {
+            // Couldn't find the extension. Assume it's openable.
+            return true;
+        }
 
-        return !this.isFileTypeExcludedInApp(ext);
+        return !this.isFileTypeExcludedInApp(regexResult[1]);
     }
 
     /**
@@ -365,7 +389,7 @@ export class CoreFileHelperProvider {
      */
     isFileTypeExcludedInApp(fileType: string): boolean {
         const currentSite = CoreSites.instance.getCurrentSite();
-        const fileTypeExcludeList = currentSite && <string> currentSite.getStoredConfig('tool_mobile_filetypeexclusionlist');
+        const fileTypeExcludeList = currentSite?.getStoredConfig('tool_mobile_filetypeexclusionlist');
 
         if (!fileTypeExcludeList) {
             return false;
diff --git a/src/app/services/file-session.ts b/src/app/services/file-session.ts
index b03cd24a6..9cbdeadc9 100644
--- a/src/app/services/file-session.ts
+++ b/src/app/services/file-session.ts
@@ -85,7 +85,7 @@ export class CoreFileSessionProvider {
      * @param id File area identifier.
      * @param siteId Site ID. If not defined, current site.
      */
-    protected initFileArea(component: string, id: string | number, siteId?: string): void {
+    protected initFileArea(component: string, id: string | number, siteId: string): void {
         if (!this.files[siteId]) {
             this.files[siteId] = {};
         }
diff --git a/src/app/services/file.ts b/src/app/services/file.ts
index c674764a7..7ad27e5cf 100644
--- a/src/app/services/file.ts
+++ b/src/app/services/file.ts
@@ -117,25 +117,25 @@ export class CoreFileProvider {
      *
      * @return Promise to be resolved when the initialization is finished.
      */
-    init(): Promise<void> {
+    async init(): Promise<void> {
         if (this.initialized) {
-            return Promise.resolve();
+            return;
         }
 
-        return Platform.instance.ready().then(() => {
-            if (CoreApp.instance.isAndroid()) {
-                this.basePath = File.instance.externalApplicationStorageDirectory || this.basePath;
-            } else if (CoreApp.instance.isIOS()) {
-                this.basePath = File.instance.documentsDirectory || this.basePath;
-            } else if (!this.isAvailable() || this.basePath === '') {
-                this.logger.error('Error getting device OS.');
+        await Platform.instance.ready();
 
-                return Promise.reject(new CoreError('Error getting device OS to initialize file system.'));
-            }
+        if (CoreApp.instance.isAndroid()) {
+            this.basePath = File.instance.externalApplicationStorageDirectory || this.basePath;
+        } else if (CoreApp.instance.isIOS()) {
+            this.basePath = File.instance.documentsDirectory || this.basePath;
+        } else if (!this.isAvailable() || this.basePath === '') {
+            this.logger.error('Error getting device OS.');
 
-            this.initialized = true;
-            this.logger.debug('FS initialized: ' + this.basePath);
-        });
+            return Promise.reject(new CoreError('Error getting device OS to initialize file system.'));
+        }
+
+        this.initialized = true;
+        this.logger.debug('FS initialized: ' + this.basePath);
     }
 
     /**
@@ -194,8 +194,12 @@ export class CoreFileProvider {
      * @param base Base path to create the dir/file in. If not set, use basePath.
      * @return Promise to be resolved when the dir/file is created.
      */
-    protected async create(isDirectory: boolean, path: string, failIfExists?: boolean, base?: string):
-            Promise<FileEntry | DirectoryEntry> {
+    protected async create(
+        isDirectory: boolean,
+        path: string,
+        failIfExists?: boolean,
+        base?: string,
+    ): Promise<FileEntry | DirectoryEntry> {
         await this.init();
 
         // Remove basePath if it's in the path.
@@ -340,17 +344,19 @@ export class CoreFileProvider {
      * @return Promise to be resolved when the size is calculated.
      */
     protected getSize(entry: DirectoryEntry | FileEntry): Promise<number> {
-        return new Promise((resolve, reject) => {
+        return new Promise<number>((resolve, reject) => {
             if (this.isDirectoryEntry(entry)) {
                 const directoryReader = entry.createReader();
 
-                directoryReader.readEntries((entries: (DirectoryEntry | FileEntry)[]) => {
-                    const promises = [];
+                directoryReader.readEntries(async (entries: (DirectoryEntry | FileEntry)[]) => {
+                    const promises: Promise<number>[] = [];
                     for (let i = 0; i < entries.length; i++) {
                         promises.push(this.getSize(entries[i]));
                     }
 
-                    Promise.all(promises).then((sizes) => {
+                    try {
+                        const sizes = await Promise.all(promises);
+
                         let directorySize = 0;
                         for (let i = 0; i < sizes.length; i++) {
                             const fileSize = Number(sizes[i]);
@@ -362,7 +368,9 @@ export class CoreFileProvider {
                             directorySize += fileSize;
                         }
                         resolve(directorySize);
-                    }, reject);
+                    } catch (error) {
+                        reject(error);
+                    }
                 }, reject);
             } else {
                 entry.file((file) => {
@@ -469,7 +477,7 @@ export class CoreFileProvider {
                     const parsed = CoreTextUtils.instance.parseJSON(text, null);
 
                     if (parsed == null && text != null) {
-                        return Promise.reject(new CoreError('Error parsing JSON file: ' + path));
+                        throw new CoreError('Error parsing JSON file: ' + path);
                     }
 
                     return parsed;
@@ -494,7 +502,7 @@ export class CoreFileProvider {
             const reader = new FileReader();
 
             reader.onloadend = (event): void => {
-                if (event.target.result !== undefined && event.target.result !== null) {
+                if (event.target?.result !== undefined && event.target.result !== null) {
                     if (format == CoreFileProvider.FORMATJSON) {
                         // Convert to object.
                         const parsed = CoreTextUtils.instance.parseJSON(<string> event.target.result, null);
@@ -507,7 +515,7 @@ export class CoreFileProvider {
                     } else {
                         resolve(event.target.result);
                     }
-                } else if (event.target.error !== undefined && event.target.error !== null) {
+                } else if (event.target?.error !== undefined && event.target.error !== null) {
                     reject(event.target.error);
                 } else {
                     reject({ code: null, message: 'READER_ONLOADEND_ERR' });
@@ -550,25 +558,27 @@ export class CoreFileProvider {
      * @param append Whether to append the data to the end of the file.
      * @return Promise to be resolved when the file is written.
      */
-    writeFile(path: string, data: string | Blob, append?: boolean): Promise<FileEntry> {
-        return this.init().then(() => {
-            // Remove basePath if it's in the path.
-            path = this.removeStartingSlash(path.replace(this.basePath, ''));
-            this.logger.debug('Write file: ' + path);
+    async writeFile(path: string, data: string | Blob, append?: boolean): Promise<FileEntry> {
+        await this.init();
 
-            // Create file (and parent folders) to prevent errors.
-            return this.createFile(path).then((fileEntry) => {
-                if (this.isHTMLAPI && !CoreApp.instance.isDesktop() &&
-                    (typeof data == 'string' || data.toString() == '[object ArrayBuffer]')) {
-                    // We need to write Blobs.
-                    const type = CoreMimetypeUtils.instance.getMimeType(CoreMimetypeUtils.instance.getFileExtension(path));
-                    data = new Blob([data], { type: type || 'text/plain' });
-                }
+        // Remove basePath if it's in the path.
+        path = this.removeStartingSlash(path.replace(this.basePath, ''));
+        this.logger.debug('Write file: ' + path);
 
-                return File.instance.writeFile(this.basePath, path, data, { replace: !append, append: !!append })
-                    .then(() => fileEntry);
-            });
-        });
+        // Create file (and parent folders) to prevent errors.
+        const fileEntry = await this.createFile(path);
+
+        if (this.isHTMLAPI && !CoreApp.instance.isDesktop() &&
+                (typeof data == 'string' || data.toString() == '[object ArrayBuffer]')) {
+            // We need to write Blobs.
+            const extension = CoreMimetypeUtils.instance.getFileExtension(path);
+            const type = extension ? CoreMimetypeUtils.instance.getMimeType(extension) : '';
+            data = new Blob([data], { type: type || 'text/plain' });
+        }
+
+        await File.instance.writeFile(this.basePath, path, data, { replace: !append, append: !!append });
+
+        return fileEntry;
     }
 
     /**
@@ -583,8 +593,13 @@ export class CoreFileProvider {
      * @param append Whether to append the data to the end of the file.
      * @return Promise resolved when done.
      */
-    async writeFileDataInFile(file: Blob, path: string, onProgress?: CoreFileProgressFunction, offset: number = 0,
-        append?: boolean): Promise<FileEntry> {
+    async writeFileDataInFile(
+        file: Blob,
+        path: string,
+        onProgress?: CoreFileProgressFunction,
+        offset: number = 0,
+        append?: boolean,
+    ): Promise<FileEntry> {
         offset = offset || 0;
 
         try {
@@ -675,16 +690,18 @@ export class CoreFileProvider {
      *
      * @return Promise to be resolved when the base path is retrieved.
      */
-    getBasePathToDownload(): Promise<string> {
-        return this.init().then(() => {
-            if (CoreApp.instance.isIOS()) {
-                // In iOS we want the internal URL (cdvfile://localhost/persistent/...).
-                return File.instance.resolveDirectoryUrl(this.basePath).then((dirEntry) => dirEntry.toInternalURL());
-            } else {
-                // In the other platforms we use the basePath as it is (file://...).
-                return this.basePath;
-            }
-        });
+    async getBasePathToDownload(): Promise<string> {
+        await this.init();
+
+        if (CoreApp.instance.isIOS()) {
+            // In iOS we want the internal URL (cdvfile://localhost/persistent/...).
+            const dirEntry = await File.instance.resolveDirectoryUrl(this.basePath);
+
+            return dirEntry.toInternalURL();
+        } else {
+            // In the other platforms we use the basePath as it is (file://...).
+            return this.basePath;
+        }
     }
 
     /**
@@ -773,18 +790,22 @@ export class CoreFileProvider {
      *                      try to create it (slower).
      * @return Promise resolved when the entry is copied.
      */
-    protected async copyOrMoveFileOrDir(from: string, to: string, isDir?: boolean, copy?: boolean, destDirExists?: boolean):
-            Promise<FileEntry | DirectoryEntry> {
+    protected async copyOrMoveFileOrDir(
+        from: string,
+        to: string,
+        isDir?: boolean,
+        copy?: boolean,
+        destDirExists?: boolean,
+    ): Promise<FileEntry | DirectoryEntry> {
         const fileIsInAppFolder = this.isPathInAppFolder(from);
 
         if (!fileIsInAppFolder) {
             return this.copyOrMoveExternalFile(from, to, copy);
         }
 
-        const moveCopyFn: (path: string, dirName: string, newPath: string, newDirName: string) =>
-            Promise<FileEntry | DirectoryEntry> = copy ?
-                (isDir ? File.instance.copyDir.bind(File.instance) : File.instance.copyFile.bind(File.instance)) :
-                (isDir ? File.instance.moveDir.bind(File.instance) : File.instance.moveFile.bind(File.instance));
+        const moveCopyFn: MoveCopyFunction = copy ?
+            (isDir ? File.instance.copyDir.bind(File.instance) : File.instance.copyFile.bind(File.instance)) :
+            (isDir ? File.instance.moveDir.bind(File.instance) : File.instance.moveFile.bind(File.instance));
 
         await this.init();
 
@@ -880,6 +901,8 @@ export class CoreFileProvider {
         if (path.indexOf(this.basePath) > -1) {
             return path.replace(this.basePath, '');
         }
+
+        return path;
     }
 
     /**
@@ -892,33 +915,31 @@ export class CoreFileProvider {
      * @param recreateDir Delete the dest directory before unzipping. Defaults to true.
      * @return Promise resolved when the file is unzipped.
      */
-    unzipFile(path: string, destFolder?: string, onProgress?: (progress: ProgressEvent) => void, recreateDir: boolean = true):
-            Promise<void> {
+    async unzipFile(
+        path: string,
+        destFolder?: string,
+        onProgress?: (progress: ProgressEvent) => void,
+        recreateDir: boolean = true,
+    ): Promise<void> {
         // Get the source file.
-        let fileEntry: FileEntry;
+        const fileEntry = await this.getFile(path);
 
-        return this.getFile(path).then((fe) => {
-            fileEntry = fe;
+        if (destFolder && recreateDir) {
+            // Make sure the dest dir doesn't exist already.
+            await CoreUtils.instance.ignoreErrors(this.removeDir(destFolder));
 
-            if (destFolder && recreateDir) {
-                // Make sure the dest dir doesn't exist already.
-                return this.removeDir(destFolder).catch(() => {
-                    // Ignore errors.
-                }).then(() =>
-                    // Now create the dir, otherwise if any of the ancestor dirs doesn't exist the unzip would fail.
-                    this.createDir(destFolder),
-                );
-            }
-        }).then(() => {
-            // If destFolder is not set, use same location as ZIP file. We need to use absolute paths (including basePath).
-            destFolder = this.addBasePathIfNeeded(destFolder || CoreMimetypeUtils.instance.removeExtension(path));
+            // Now create the dir, otherwise if any of the ancestor dirs doesn't exist the unzip would fail.
+            await this.createDir(destFolder);
+        }
 
-            return Zip.instance.unzip(fileEntry.toURL(), destFolder, onProgress);
-        }).then((result) => {
-            if (result == -1) {
-                return Promise.reject(new CoreError('Unzip failed.'));
-            }
-        });
+        // If destFolder is not set, use same location as ZIP file. We need to use absolute paths (including basePath).
+        destFolder = this.addBasePathIfNeeded(destFolder || CoreMimetypeUtils.instance.removeExtension(path));
+
+        const result = await Zip.instance.unzip(fileEntry.toURL(), destFolder, onProgress);
+
+        if (result == -1) {
+            throw new CoreError('Unzip failed.');
+        }
     }
 
     /**
@@ -999,22 +1020,22 @@ export class CoreFileProvider {
      * @param copy True to copy, false to move.
      * @return Promise resolved when the entry is copied/moved.
      */
-    protected copyOrMoveExternalFile(from: string, to: string, copy?: boolean): Promise<FileEntry> {
+    protected async copyOrMoveExternalFile(from: string, to: string, copy?: boolean): Promise<FileEntry> {
         // Get the file to copy/move.
-        return this.getExternalFile(from).then((fileEntry) => {
-            // Create the destination dir if it doesn't exist.
-            const dirAndFile = this.getFileAndDirectoryFromPath(to);
+        const fileEntry = await this.getExternalFile(from);
 
-            return this.createDir(dirAndFile.directory).then((dirEntry) =>
-                // Now copy/move the file.
-                new Promise((resolve, reject): void => {
-                    if (copy) {
-                        fileEntry.copyTo(dirEntry, dirAndFile.name, (entry: FileEntry) => resolve(entry), reject);
-                    } else {
-                        fileEntry.moveTo(dirEntry, dirAndFile.name, (entry: FileEntry) => resolve(entry), reject);
-                    }
-                }),
-            );
+        // Create the destination dir if it doesn't exist.
+        const dirAndFile = this.getFileAndDirectoryFromPath(to);
+
+        const dirEntry = await this.createDir(dirAndFile.directory);
+
+        // Now copy/move the file.
+        return new Promise((resolve, reject): void => {
+            if (copy) {
+                fileEntry.copyTo(dirEntry, dirAndFile.name, (entry: FileEntry) => resolve(entry), reject);
+            } else {
+                fileEntry.moveTo(dirEntry, dirAndFile.name, (entry: FileEntry) => resolve(entry), reject);
+            }
         });
     }
 
@@ -1048,9 +1069,11 @@ export class CoreFileProvider {
      * @param defaultExt Default extension to use if no extension found in the file.
      * @return Promise resolved with the unique file name.
      */
-    getUniqueNameInFolder(dirPath: string, fileName: string, defaultExt?: string): Promise<string> {
+    async getUniqueNameInFolder(dirPath: string, fileName: string, defaultExt?: string): Promise<string> {
         // Get existing files in the folder.
-        return this.getDirectoryContents(dirPath).then((entries) => {
+        try {
+            const entries = await this.getDirectoryContents(dirPath);
+
             const files = {};
             let num = 1;
             let fileNameWithoutExtension = CoreMimetypeUtils.instance.removeExtension(fileName);
@@ -1058,7 +1081,8 @@ export class CoreFileProvider {
 
             // Clean the file name.
             fileNameWithoutExtension = CoreTextUtils.instance.removeSpecialCharactersForFiles(
-                CoreTextUtils.instance.decodeURIComponent(fileNameWithoutExtension));
+                CoreTextUtils.instance.decodeURIComponent(fileNameWithoutExtension),
+            );
 
             // Index the files by name.
             entries.forEach((entry) => {
@@ -1086,10 +1110,10 @@ export class CoreFileProvider {
                 // Ask the user what he wants to do.
                 return newName;
             }
-        }).catch(() =>
+        } catch (error) {
             // Folder doesn't exist, name is unique. Clean it and return it.
-            CoreTextUtils.instance.removeSpecialCharactersForFiles(CoreTextUtils.instance.decodeURIComponent(fileName)),
-        );
+            return CoreTextUtils.instance.removeSpecialCharactersForFiles(CoreTextUtils.instance.decodeURIComponent(fileName));
+        }
     }
 
     /**
@@ -1119,7 +1143,7 @@ export class CoreFileProvider {
             }
 
             const filesMap: {[fullPath: string]: FileEntry} = {};
-            const promises = [];
+            const promises: Promise<void>[] = [];
 
             // Index the received files by fullPath and ignore the invalid ones.
             files.forEach((file) => {
@@ -1219,3 +1243,5 @@ export class CoreFileProvider {
 }
 
 export class CoreFile extends makeSingleton(CoreFileProvider) {}
+
+type MoveCopyFunction = (path: string, dirName: string, newPath: string, newDirName: string) => Promise<FileEntry | DirectoryEntry>;
diff --git a/src/app/services/filepool.ts b/src/app/services/filepool.ts
index b910c9334..dd602a123 100644
--- a/src/app/services/filepool.ts
+++ b/src/app/services/filepool.ts
@@ -239,7 +239,7 @@ export class CoreFilepoolProvider {
     protected logger: CoreLogger;
     protected appDB: SQLiteDB;
     protected dbReady: Promise<void>; // Promise resolved when the app DB is initialized.
-    protected queueState: string;
+    protected queueState = CoreFilepoolProvider.QUEUE_PAUSED;
     protected urlAttributes: RegExp[] = [
         new RegExp('(\\?|&)token=([A-Za-z0-9]*)'),
         new RegExp('(\\?|&)forcedownload=[0-1]'),
@@ -264,16 +264,23 @@ export class CoreFilepoolProvider {
 
         CoreSites.instance.registerSiteSchema(this.siteSchema);
 
-        CoreInit.instance.ready().then(() => {
-            // Waiting for the app to be ready to start processing the queue.
-            this.checkQueueProcessing();
+        this.init();
+    }
 
-            // Start queue when device goes online.
-            Network.instance.onConnect().subscribe(() => {
-                // Execute the callback in the Angular zone, so change detection doesn't stop working.
-                NgZone.instance.run(() => {
-                    this.checkQueueProcessing();
-                });
+    /**
+     * Init some properties.
+     */
+    protected async init(): Promise<void> {
+        // Waiting for the app to be ready to start processing the queue.
+        await CoreInit.instance.ready();
+
+        this.checkQueueProcessing();
+
+        // Start queue when device goes online.
+        Network.instance.onConnect().subscribe(() => {
+            // Execute the callback in the Angular zone, so change detection doesn't stop working.
+            NgZone.instance.run(() => {
+                this.checkQueueProcessing();
             });
         });
     }
@@ -358,7 +365,7 @@ export class CoreFilepoolProvider {
      * @param data Additional information to store about the file (timemodified, url, ...). See FILES_TABLE schema.
      * @return Promise resolved on success.
      */
-    protected async addFileToPool(siteId: string, fileId: string, data: CoreFilepoolFileEntry): Promise<void> {
+    protected async addFileToPool(siteId: string, fileId: string, data: Omit<CoreFilepoolFileEntry, 'fileId'>): Promise<void> {
         const record = {
             fileId,
             ...data,
@@ -410,9 +417,18 @@ export class CoreFilepoolProvider {
      * @param link The link to add for the file.
      * @return Promise resolved when the file is downloaded.
      */
-    protected async addToQueue(siteId: string, fileId: string, url: string, priority: number, revision: number,
-            timemodified: number, filePath: string, onProgress?: CoreFilepoolOnProgressCallback,
-            options: CoreFilepoolFileOptions = {}, link?: CoreFilepoolComponentLink): Promise<void> {
+    protected async addToQueue(
+        siteId: string,
+        fileId: string,
+        url: string,
+        priority: number,
+        revision: number,
+        timemodified: number,
+        filePath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+        options: CoreFilepoolFileOptions = {},
+        link?: CoreFilepoolComponentLink,
+    ): Promise<void> {
         await this.dbReady;
 
         this.logger.debug(`Adding ${fileId} to the queue`);
@@ -454,9 +470,19 @@ export class CoreFilepoolProvider {
      * @param alreadyFixed Whether the URL has already been fixed.
      * @return Resolved on success.
      */
-    async addToQueueByUrl(siteId: string, fileUrl: string, component?: string, componentId?: string | number,
-            timemodified: number = 0, filePath?: string, onProgress?: CoreFilepoolOnProgressCallback, priority: number = 0,
-            options: CoreFilepoolFileOptions = {}, revision?: number, alreadyFixed?: boolean): Promise<void> {
+    async addToQueueByUrl(
+        siteId: string,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified: number = 0,
+        filePath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+        priority: number = 0,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+        alreadyFixed?: boolean,
+    ): Promise<void> {
         await this.dbReady;
 
         if (!CoreFile.instance.isAvailable()) {
@@ -468,16 +494,14 @@ export class CoreFilepoolProvider {
             throw new CoreError('Site doesn\'t allow downloading files.');
         }
 
-        let file: CoreWSExternalFile;
-        if (alreadyFixed) {
-            // Already fixed, if we reached here it means it can be downloaded.
-            file = { fileurl: fileUrl };
-        } else {
-            file = await this.fixPluginfileURL(siteId, fileUrl);
+        if (!alreadyFixed) {
+            // Fix the URL and use the fixed data.
+            const file = await this.fixPluginfileURL(siteId, fileUrl);
+
+            fileUrl = file.fileurl;
+            timemodified = file.timemodified || timemodified;
         }
 
-        fileUrl = file.fileurl;
-        timemodified = file.timemodified || timemodified;
         revision = revision || this.getRevisionFromUrl(fileUrl);
         const fileId = this.getFileIdByUrl(fileUrl);
 
@@ -489,71 +513,68 @@ export class CoreFilepoolProvider {
         // Retrieve the queue deferred now if it exists.
         // This is to prevent errors if file is removed from queue while we're checking if the file is in queue.
         const queueDeferred = this.getQueueDeferred(siteId, fileId, false, onProgress);
+        let entry: CoreFilepoolQueueEntry;
 
-        return this.hasFileInQueue(siteId, fileId).then((entry: CoreFilepoolQueueEntry) => {
-            const newData: CoreFilepoolQueueDBEntry = {};
-            let foundLink = false;
-
-            if (entry) {
-                // We already have the file in queue, we update the priority and links.
-                if (entry.priority < priority) {
-                    newData.priority = priority;
-                }
-                if (revision && entry.revision !== revision) {
-                    newData.revision = revision;
-                }
-                if (timemodified && entry.timemodified !== timemodified) {
-                    newData.timemodified = timemodified;
-                }
-                if (filePath && entry.path !== filePath) {
-                    newData.path = filePath;
-                }
-                if (entry.isexternalfile !== options.isexternalfile && (entry.isexternalfile || options.isexternalfile)) {
-                    newData.isexternalfile = options.isexternalfile;
-                }
-                if (entry.repositorytype !== options.repositorytype && (entry.repositorytype || options.repositorytype)) {
-                    newData.repositorytype = options.repositorytype;
-                }
-
-                if (link) {
-                    // We need to add the new link if it does not exist yet.
-                    if (entry.linksUnserialized && entry.linksUnserialized.length) {
-                        foundLink = entry.linksUnserialized.some((fileLink) =>
-                            fileLink.component == link.component && fileLink.componentId == link.componentId);
-                    }
-
-                    if (!foundLink) {
-                        const links = entry.linksUnserialized || [];
-                        links.push(link);
-                        newData.links = JSON.stringify(links);
-                    }
-                }
-
-                if (Object.keys(newData).length) {
-                    // Update only when required.
-                    this.logger.debug(`Updating file ${fileId} which is already in queue`);
-
-                    return this.appDB.updateRecords(CoreFilepoolProvider.QUEUE_TABLE, newData, primaryKey).then(() =>
-                        this.getQueuePromise(siteId, fileId, true, onProgress));
-                }
-
-                this.logger.debug(`File ${fileId} already in queue and does not require update`);
-                if (queueDeferred) {
-                    // If we were able to retrieve the queue deferred before, we use that one.
-                    return queueDeferred.promise;
-                } else {
-                    // Create a new deferred and return its promise.
-                    return this.getQueuePromise(siteId, fileId, true, onProgress);
-                }
-            } else {
-                return this.addToQueue(
-                    siteId, fileId, fileUrl, priority, revision, timemodified, filePath, onProgress, options, link);
-            }
-        }, () =>
+        try {
+            entry = await this.hasFileInQueue(siteId, fileId);
+        } catch (error) {
             // Unsure why we could not get the record, let's add to the queue anyway.
-            this.addToQueue(
-                siteId, fileId, fileUrl, priority, revision, timemodified, filePath, onProgress, options, link),
-        );
+            return this.addToQueue(siteId, fileId, fileUrl, priority, revision, timemodified, filePath, onProgress, options, link);
+        }
+
+        const newData: Partial<CoreFilepoolQueueDBEntry> = {};
+        let foundLink = false;
+
+        // We already have the file in queue, we update the priority and links.
+        if (!entry.priority || entry.priority < priority) {
+            newData.priority = priority;
+        }
+        if (revision && entry.revision !== revision) {
+            newData.revision = revision;
+        }
+        if (timemodified && entry.timemodified !== timemodified) {
+            newData.timemodified = timemodified;
+        }
+        if (filePath && entry.path !== filePath) {
+            newData.path = filePath;
+        }
+        if (entry.isexternalfile !== options.isexternalfile && (entry.isexternalfile || options.isexternalfile)) {
+            newData.isexternalfile = options.isexternalfile;
+        }
+        if (entry.repositorytype !== options.repositorytype && (entry.repositorytype || options.repositorytype)) {
+            newData.repositorytype = options.repositorytype;
+        }
+
+        if (link) {
+            // We need to add the new link if it does not exist yet.
+            if (entry.linksUnserialized && entry.linksUnserialized.length) {
+                foundLink = entry.linksUnserialized.some((fileLink) =>
+                    fileLink.component == link.component && fileLink.componentId == link.componentId);
+            }
+
+            if (!foundLink) {
+                const links = entry.linksUnserialized || [];
+                links.push(link);
+                newData.links = JSON.stringify(links);
+            }
+        }
+
+        if (Object.keys(newData).length) {
+            // Update only when required.
+            this.logger.debug(`Updating file ${fileId} which is already in queue`);
+
+            return this.appDB.updateRecords(CoreFilepoolProvider.QUEUE_TABLE, newData, primaryKey).then(() =>
+                this.getQueuePromise(siteId, fileId, true, onProgress));
+        }
+
+        this.logger.debug(`File ${fileId} already in queue and does not require update`);
+        if (queueDeferred) {
+            // If we were able to retrieve the queue deferred before, we use that one.
+            return queueDeferred.promise;
+        } else {
+            // Create a new deferred and return its promise.
+            return this.getQueuePromise(siteId, fileId, true, onProgress);
+        }
     }
 
     /**
@@ -571,13 +592,32 @@ export class CoreFilepoolProvider {
      * @param revision File revision. If not defined, it will be calculated using the URL.
      * @return Promise resolved when the file is downloaded.
      */
-    protected async addToQueueIfNeeded(siteId: string, fileUrl: string, component: string, componentId?: string | number,
-            timemodified: number = 0, checkSize: boolean = true, downloadUnknown?: boolean, options: CoreFilepoolFileOptions = {},
-            revision?: number): Promise<void> {
+    protected async addToQueueIfNeeded(
+        siteId: string,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified: number = 0,
+        checkSize: boolean = true,
+        downloadUnknown?: boolean,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+    ): Promise<void> {
         if (!checkSize) {
             // No need to check size, just add it to the queue.
-            await this.addToQueueByUrl(siteId, fileUrl, component, componentId, timemodified, undefined, undefined, 0, options,
-                revision, true);
+            await this.addToQueueByUrl(
+                siteId,
+                fileUrl,
+                component,
+                componentId,
+                timemodified,
+                undefined,
+                undefined,
+                0,
+                options,
+                revision,
+                true,
+            );
         }
 
         let size: number;
@@ -603,14 +643,20 @@ export class CoreFilepoolProvider {
         }
 
         // Check if the file should be downloaded.
-        if (sizeUnknown) {
-            if (downloadUnknown && isWifi) {
-                await this.addToQueueByUrl(siteId, fileUrl, component, componentId, timemodified, undefined, undefined,
-                    0, options, revision, true);
-            }
-        } else if (this.shouldDownload(size)) {
-            await this.addToQueueByUrl(siteId, fileUrl, component, componentId, timemodified, undefined, undefined, 0,
-                options, revision, true);
+        if ((sizeUnknown && downloadUnknown && isWifi) || (!sizeUnknown && this.shouldDownload(size))) {
+            await this.addToQueueByUrl(
+                siteId,
+                fileUrl,
+                component,
+                componentId,
+                timemodified,
+                undefined,
+                undefined,
+                0,
+                options,
+                revision,
+                true,
+            );
         }
     }
 
@@ -699,12 +745,10 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Link, null if nothing to link.
      */
-    protected createComponentLink(component: string, componentId?: string | number): CoreFilepoolComponentLink | null {
+    protected createComponentLink(component?: string, componentId?: string | number): CoreFilepoolComponentLink | undefined {
         if (typeof component != 'undefined' && component != null)  {
             return { component, componentId: this.fixComponentId(componentId) };
         }
-
-        return null;
     }
 
     /**
@@ -714,7 +758,7 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Links.
      */
-    protected createComponentLinks(component: string, componentId?: string | number): CoreFilepoolComponentLink[] {
+    protected createComponentLinks(component?: string, componentId?: string | number): CoreFilepoolComponentLink[] {
         const link = this.createComponentLink(component, componentId);
 
         return link ? [link] : [];
@@ -772,12 +816,18 @@ export class CoreFilepoolProvider {
      * @param poolFileObject When set, the object will be updated, a new entry will not be created.
      * @return Resolved with internal URL on success, rejected otherwise.
      */
-    protected async downloadForPoolByUrl(siteId: string, fileUrl: string, options: CoreFilepoolFileOptions = {}, filePath?: string,
-            onProgress?: CoreFilepoolOnProgressCallback, poolFileObject?: CoreFilepoolFileEntry): Promise<string> {
+    protected async downloadForPoolByUrl(
+        siteId: string,
+        fileUrl: string,
+        options: CoreFilepoolFileOptions = {},
+        filePath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+        poolFileObject?: CoreFilepoolFileEntry,
+    ): Promise<string> {
         const fileId = this.getFileIdByUrl(fileUrl);
         const extension = CoreMimetypeUtils.instance.guessExtensionFromUrl(fileUrl);
         const addExtension = typeof filePath == 'undefined';
-        filePath = filePath || (await this.getFilePath(siteId, fileId, extension));
+        const path = filePath || (await this.getFilePath(siteId, fileId, extension));
 
         if (poolFileObject && poolFileObject.fileId !== fileId) {
             this.logger.error('Invalid object to update passed');
@@ -785,7 +835,7 @@ export class CoreFilepoolProvider {
             throw new CoreError('Invalid object to update passed.');
         }
 
-        const downloadId = this.getFileDownloadId(fileUrl, filePath);
+        const downloadId = this.getFileDownloadId(fileUrl, path);
 
         if (this.filePromises[siteId] && this.filePromises[siteId][downloadId]) {
             // There's already a download ongoing for this file in this location, return the promise.
@@ -799,22 +849,21 @@ export class CoreFilepoolProvider {
                 throw new CoreError('Site doesn\'t allow downloading files.');
             }
 
-            const entry = await CoreWS.instance.downloadFile(fileUrl, filePath, addExtension, onProgress);
+            const entry = await CoreWS.instance.downloadFile(fileUrl, path, addExtension, onProgress);
             const fileEntry = entry;
             await CorePluginFile.instance.treatDownloadedFile(fileUrl, fileEntry, siteId, onProgress);
 
-            const data: CoreFilepoolFileEntry = poolFileObject || {};
-            data.downloadTime = Date.now();
-            data.stale = 0;
-            data.url = fileUrl;
-            data.revision = options.revision;
-            data.timemodified = options.timemodified;
-            data.isexternalfile = options.isexternalfile ? 1 : 0;
-            data.repositorytype = options.repositorytype;
-            data.path = fileEntry.path;
-            data.extension = fileEntry.extension;
-
-            await this.addFileToPool(siteId, fileId, data);
+            await this.addFileToPool(siteId, fileId, {
+                downloadTime: Date.now(),
+                stale: 0,
+                url: fileUrl,
+                revision: options.revision,
+                timemodified: options.timemodified,
+                isexternalfile: options.isexternalfile ? 1 : 0,
+                repositorytype: options.repositorytype,
+                path: fileEntry.path,
+                extension: fileEntry.extension,
+            });
 
             return fileEntry.toURL();
         }).finally(() => {
@@ -838,9 +887,16 @@ export class CoreFilepoolProvider {
      *                the files directly inside the filepool folder.
      * @return Resolved on success.
      */
-    downloadOrPrefetchFiles(siteId: string, files: CoreWSExternalFile[], prefetch: boolean, ignoreStale?: boolean,
-            component?: string, componentId?: string | number, dirPath?: string): Promise<void> {
-        const promises = [];
+    downloadOrPrefetchFiles(
+        siteId: string,
+        files: CoreWSExternalFile[],
+        prefetch: boolean,
+        ignoreStale?: boolean,
+        component?: string,
+        componentId?: string | number,
+        dirPath?: string,
+    ): Promise<void> {
+        const promises: Promise<unknown>[] = [];
 
         // Download files.
         files.forEach((file) => {
@@ -850,23 +906,31 @@ export class CoreFilepoolProvider {
                 isexternalfile: file.isexternalfile,
                 repositorytype: file.repositorytype,
             };
-            let path: string;
+            let path: string | undefined;
 
             if (dirPath) {
                 // Calculate the path to the file.
                 path = file.filename;
-                if (file.filepath !== '/') {
+                if (file.filepath && file.filepath !== '/') {
                     path = file.filepath.substr(1) + path;
                 }
-                path = CoreTextUtils.instance.concatenatePaths(dirPath, path);
+                path = CoreTextUtils.instance.concatenatePaths(dirPath, path!);
             }
 
             if (prefetch) {
-                promises.push(this.addToQueueByUrl(
-                    siteId, url, component, componentId, timemodified, path, undefined, 0, options));
+                promises.push(this.addToQueueByUrl(siteId, url, component, componentId, timemodified, path, undefined, 0, options));
             } else {
                 promises.push(this.downloadUrl(
-                    siteId, url, ignoreStale, component, componentId, timemodified, undefined, path, options));
+                    siteId,
+                    url,
+                    ignoreStale,
+                    component,
+                    componentId,
+                    timemodified,
+                    undefined,
+                    path,
+                    options,
+                ));
             }
         });
 
@@ -887,9 +951,16 @@ export class CoreFilepoolProvider {
      * @param onProgress Function to call on progress.
      * @return Promise resolved when the package is downloaded.
      */
-    protected downloadOrPrefetchPackage(siteId: string, fileList: CoreWSExternalFile[], prefetch?: boolean, component?: string,
-            componentId?: string | number, extra?: string, dirPath?: string, onProgress?: CoreFilepoolOnProgressCallback):
-            Promise<void> {
+    protected downloadOrPrefetchPackage(
+        siteId: string,
+        fileList: CoreWSExternalFile[],
+        prefetch: boolean,
+        component: string,
+        componentId?: string | number,
+        extra?: string,
+        dirPath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+    ): Promise<void> {
         const packageId = this.getPackageId(component, componentId);
 
         if (this.packagesPromises[siteId] && this.packagesPromises[siteId][packageId]) {
@@ -901,7 +972,7 @@ export class CoreFilepoolProvider {
 
         // Set package as downloading.
         const promise = this.storePackageStatus(siteId, CoreConstants.DOWNLOADING, component, componentId).then(async () => {
-            const promises = [];
+            const promises: Promise<string | void>[] = [];
             let packageLoaded = 0;
 
             fileList.forEach((file) => {
@@ -910,10 +981,10 @@ export class CoreFilepoolProvider {
                     isexternalfile: file.isexternalfile,
                     repositorytype: file.repositorytype,
                 };
-                let path: string;
+                let path: string | undefined;
                 let promise: Promise<string | void>;
                 let fileLoaded = 0;
-                let onFileProgress: (progress: ProgressEvent) => void;
+                let onFileProgress: ((progress: ProgressEvent) => void) | undefined;
 
                 if (onProgress) {
                     // There's a onProgress event, create a function to receive file download progress events.
@@ -934,18 +1005,36 @@ export class CoreFilepoolProvider {
                 if (dirPath) {
                     // Calculate the path to the file.
                     path = file.filename;
-                    if (file.filepath !== '/') {
+                    if (file.filepath && file.filepath !== '/') {
                         path = file.filepath.substr(1) + path;
                     }
-                    path = CoreTextUtils.instance.concatenatePaths(dirPath, path);
+                    path = CoreTextUtils.instance.concatenatePaths(dirPath, path!);
                 }
 
                 if (prefetch) {
                     promise = this.addToQueueByUrl(
-                        siteId, fileUrl, component, componentId, file.timemodified, path, undefined, 0, options);
+                        siteId,
+                        fileUrl,
+                        component,
+                        componentId,
+                        file.timemodified,
+                        path,
+                        undefined,
+                        0,
+                        options,
+                    );
                 } else {
                     promise = this.downloadUrl(
-                        siteId, fileUrl, false, component, componentId, file.timemodified, onFileProgress, path, options);
+                        siteId,
+                        fileUrl,
+                        false,
+                        component,
+                        componentId,
+                        file.timemodified,
+                        onFileProgress,
+                        path,
+                        options,
+                    );
                 }
 
                 // Using undefined for success & fail will pass the success/failure to the parent promise.
@@ -956,6 +1045,8 @@ export class CoreFilepoolProvider {
                 await Promise.all(promises);
                 // Success prefetching, store package as downloaded.
                 await this.storePackageStatus(siteId, CoreConstants.DOWNLOADED, component, componentId, extra);
+
+                return;
             } catch (error) {
                 // Error downloading, go back to previous status and reject the promise.
                 await this.setPackagePreviousStatus(siteId, component, componentId);
@@ -985,8 +1076,15 @@ export class CoreFilepoolProvider {
      * @param onProgress Function to call on progress.
      * @return Promise resolved when all files are downloaded.
      */
-    downloadPackage(siteId: string, fileList: CoreWSExternalFile[], component: string, componentId?: string | number,
-            extra?: string, dirPath?: string, onProgress?: CoreFilepoolOnProgressCallback): Promise<void> {
+    downloadPackage(
+        siteId: string,
+        fileList: CoreWSExternalFile[],
+        component: string,
+        componentId?: string | number,
+        extra?: string,
+        dirPath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+    ): Promise<void> {
         return this.downloadOrPrefetchPackage(siteId, fileList, false, component, componentId, extra, dirPath, onProgress);
     }
 
@@ -1010,10 +1108,18 @@ export class CoreFilepoolProvider {
      * not force a file to be re-downloaded if it is already part of the pool. You should mark a file as stale using
      * invalidateFileByUrl to trigger a download.
      */
-    async downloadUrl(siteId: string, fileUrl: string, ignoreStale?: boolean, component?: string, componentId?: string | number,
-            timemodified: number = 0, onProgress?: CoreFilepoolOnProgressCallback, filePath?: string,
-            options: CoreFilepoolFileOptions = {}, revision?: number): Promise<string> {
-        let promise: Promise<string>;
+    async downloadUrl(
+        siteId: string,
+        fileUrl: string,
+        ignoreStale?: boolean,
+        component?: string,
+        componentId?: string | number,
+        timemodified: number = 0,
+        onProgress?: CoreFilepoolOnProgressCallback,
+        filePath?: string,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+    ): Promise<string> {
         let alreadyDownloaded = true;
 
         if (!CoreFile.instance.isAvailable()) {
@@ -1031,47 +1137,9 @@ export class CoreFilepoolProvider {
 
         const links = this.createComponentLinks(component, componentId);
 
-        return this.hasFileInPool(siteId, fileId).then((fileObject) => {
-            if (typeof fileObject === 'undefined') {
-                // We do not have the file, download and add to pool.
-                this.notifyFileDownloading(siteId, fileId, links);
-                alreadyDownloaded = false;
-
-                return this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress);
-            } else if (this.isFileOutdated(fileObject, options.revision, options.timemodified) &&
-                    CoreApp.instance.isOnline() && !ignoreStale) {
-                // The file is outdated, force the download and update it.
-                this.notifyFileDownloading(siteId, fileId, links);
-                alreadyDownloaded = false;
-
-                return this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress, fileObject);
-            }
-
-            // Everything is fine, return the file on disk.
-            if (filePath) {
-                promise = this.getInternalUrlByPath(filePath);
-            } else {
-                promise = this.getInternalUrlById(siteId, fileId);
-            }
-
-            return promise.then((url) => url, () => {
-                // The file was not found in the pool, weird.
-                this.notifyFileDownloading(siteId, fileId, links);
-                alreadyDownloaded = false;
-
-                return this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress, fileObject);
-            });
-        }, () => {
-            // The file is not in the pool just yet.
-            this.notifyFileDownloading(siteId, fileId, links);
-            alreadyDownloaded = false;
-
-            return this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress);
-        }).then((url) => {
+        const finishSuccessfulDownload = (url: string): string => {
             if (typeof component != 'undefined') {
-                this.addFileLink(siteId, fileId, component, componentId).catch(() => {
-                    // Ignore errors.
-                });
+                CoreUtils.instance.ignoreErrors(this.addFileLink(siteId, fileId, component, componentId));
             }
 
             if (!alreadyDownloaded) {
@@ -1079,11 +1147,43 @@ export class CoreFilepoolProvider {
             }
 
             return url;
-        }, (err) => {
-            this.notifyFileDownloadError(siteId, fileId, links);
+        };
 
-            return Promise.reject(err);
-        });
+        try {
+            const fileObject = await this.hasFileInPool(siteId, fileId);
+            let url: string;
+
+            if (!fileObject ||
+                this.isFileOutdated(fileObject, options.revision, options.timemodified) &&
+                CoreApp.instance.isOnline() &&
+                !ignoreStale
+            ) {
+                throw new CoreError('Needs to be downloaded');
+            }
+
+            // File downloaded and not outdated, return the file from disk.
+            if (filePath) {
+                url = await this.getInternalUrlByPath(filePath);
+            } else {
+                url = await this.getInternalUrlById(siteId, fileId);
+            }
+
+            return finishSuccessfulDownload(url);
+        } catch (error) {
+            // The file is not downloaded or it's outdated.
+            this.notifyFileDownloading(siteId, fileId, links);
+            alreadyDownloaded = false;
+
+            try {
+                const url = await this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress);
+
+                return finishSuccessfulDownload(url);
+            } catch (error) {
+                this.notifyFileDownloadError(siteId, fileId, links);
+
+                throw error;
+            }
+        }
     }
 
     /**
@@ -1093,15 +1193,14 @@ export class CoreFilepoolProvider {
      * @return List of file urls.
      */
     extractDownloadableFilesFromHtml(html: string): string[] {
-        let urls = [];
+        let urls: string[] = [];
 
         const element = CoreDomUtils.instance.convertToElement(html);
-        const elements: (HTMLAnchorElement | HTMLImageElement | HTMLAudioElement | HTMLVideoElement | HTMLSourceElement |
-            HTMLTrackElement)[] = Array.from(element.querySelectorAll('a, img, audio, video, source, track'));
+        const elements: AnchorOrMediaElement[] = Array.from(element.querySelectorAll('a, img, audio, video, source, track'));
 
         for (let i = 0; i < elements.length; i++) {
             const element = elements[i];
-            let url = 'href' in element ? element.href : element.src;
+            const url = 'href' in element ? element.href : element.src;
 
             if (url && CoreUrlUtils.instance.isDownloadableUrl(url) && urls.indexOf(url) == -1) {
                 urls.push(url);
@@ -1109,9 +1208,9 @@ export class CoreFilepoolProvider {
 
             // Treat video poster.
             if (element.tagName == 'VIDEO' && element.getAttribute('poster')) {
-                url = element.getAttribute('poster');
-                if (url && CoreUrlUtils.instance.isDownloadableUrl(url) && urls.indexOf(url) == -1) {
-                    urls.push(url);
+                const poster = element.getAttribute('poster');
+                if (poster && CoreUrlUtils.instance.isDownloadableUrl(poster) && urls.indexOf(poster) == -1) {
+                    urls.push(poster);
                 }
             }
         }
@@ -1186,20 +1285,20 @@ export class CoreFilepoolProvider {
      * @param componentId The component ID.
      * @return The normalised component ID. -1 when undefined was passed.
      */
-    protected fixComponentId(componentId: string | number): string | number {
+    protected fixComponentId(componentId?: string | number): string | number {
         if (typeof componentId == 'number') {
             return componentId;
         }
 
+        if (typeof componentId == 'undefined' || componentId === null) {
+            return -1;
+        }
+
         // Try to convert it to a number.
         const id = parseInt(componentId, 10);
         if (isNaN(id)) {
             // Not a number.
-            if (typeof componentId == 'undefined' || componentId === null) {
-                return -1;
-            } else {
-                return componentId;
-            }
+            return componentId;
         }
 
         return id;
@@ -1230,8 +1329,11 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Promise resolved with the files.
      */
-    protected async getComponentFiles(db: SQLiteDB, component: string, componentId?: string | number):
-            Promise<CoreFilepoolLinksRecord[]> {
+    protected async getComponentFiles(
+        db: SQLiteDB,
+        component: string,
+        componentId?: string | number,
+    ): Promise<CoreFilepoolLinksRecord[]> {
         const conditions = {
             component,
             componentId: this.fixComponentId(componentId),
@@ -1420,25 +1522,24 @@ export class CoreFilepoolProvider {
     async getFilesByComponent(siteId: string, component: string, componentId?: string | number): Promise<CoreFilepoolFileEntry[]> {
         const db = await CoreSites.instance.getSiteDb(siteId);
         const items = await this.getComponentFiles(db, component, componentId);
-        const files = [];
+        const files: CoreFilepoolFileEntry[] = [];
+
+        await Promise.all(items.map(async (item) => {
+            try {
+                const fileEntry = await db.getRecord<CoreFilepoolFileEntry>(
+                    CoreFilepoolProvider.FILES_TABLE,
+                    { fileId: item.fileId },
+                );
 
-        const promises = items.map((item) =>
-            db.getRecord<CoreFilepoolFileEntry>(CoreFilepoolProvider.FILES_TABLE, { fileId: item.fileId }).then((fileEntry) => {
                 if (!fileEntry) {
                     return;
                 }
 
-                files.push({
-                    url: fileEntry.url,
-                    path: fileEntry.path,
-                    extension: fileEntry.extension,
-                    revision: fileEntry.revision,
-                    timemodified: fileEntry.timemodified,
-                });
-            }).catch(() => {
-            // File not found, ignore error.
-            }));
-        await Promise.all(promises);
+                files.push(fileEntry);
+            } catch (error) {
+                // File not found, ignore error.
+            }
+        }));
 
         return files;
     }
@@ -1451,21 +1552,22 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Promise resolved with the size on success.
      */
-    getFilesSizeByComponent(siteId: string, component: string, componentId?: string | number): Promise<number> {
-        return this.getFilesByComponent(siteId, component, componentId).then((files) => {
-            const promises = [];
-            let size = 0;
+    async getFilesSizeByComponent(siteId: string, component: string, componentId?: string | number): Promise<number> {
+        const files = await this.getFilesByComponent(siteId, component, componentId);
 
-            files.forEach((file) => {
-                promises.push(CoreFile.instance.getFileSize(file.path).then((fs) => {
-                    size += fs;
-                }).catch(() => {
-                    // Ignore failures, maybe some file was deleted.
-                }));
-            });
+        let size = 0;
 
-            return Promise.all(promises).then(() => size);
-        });
+        await Promise.all(files.map(async (file) => {
+            try {
+                const fileSize = await CoreFile.instance.getFileSize(file.path);
+
+                size += fileSize;
+            } catch (error) {
+                // Ignore failures, maybe some file was deleted.
+            }
+        }));
+
+        return size;
     }
 
     /**
@@ -1478,8 +1580,13 @@ export class CoreFilepoolProvider {
      * @param revision File revision. If not defined, it will be calculated using the URL.
      * @return Promise resolved with the file state.
      */
-    async getFileStateByUrl(siteId: string, fileUrl: string, timemodified: number = 0, filePath?: string, revision?: number):
-            Promise<string> {
+    async getFileStateByUrl(
+        siteId: string,
+        fileUrl: string,
+        timemodified: number = 0,
+        filePath?: string,
+        revision?: number,
+    ): Promise<string> {
         let file: CoreWSExternalFile;
 
         try {
@@ -1545,65 +1652,73 @@ export class CoreFilepoolProvider {
      * This handles the queue and validity of the file. If there is a local file and it's valid, return the local URL.
      * If the file isn't downloaded or it's outdated, return the online URL and add it to the queue to be downloaded later.
      */
-    protected async getFileUrlByUrl(siteId: string, fileUrl: string, component: string, componentId?: string | number,
-            mode: string = 'url', timemodified: number = 0, checkSize: boolean = true, downloadUnknown?: boolean,
-            options: CoreFilepoolFileOptions = {}, revision?: number): Promise<string> {
+    protected async getFileUrlByUrl(
+        siteId: string,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        mode: string = 'url',
+        timemodified: number = 0,
+        checkSize: boolean = true,
+        downloadUnknown?: boolean,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+    ): Promise<string> {
         const addToQueue = (fileUrl: string): void => {
             // Add the file to queue if needed and ignore errors.
-            this.addToQueueIfNeeded(siteId, fileUrl, component, componentId, timemodified, checkSize,
-                downloadUnknown, options, revision).catch(() => {
-                // Ignore errors.
-            });
+            CoreUtils.instance.ignoreErrors(this.addToQueueIfNeeded(
+                siteId,
+                fileUrl,
+                component,
+                componentId,
+                timemodified,
+                checkSize,
+                downloadUnknown,
+                options,
+                revision,
+            ));
         };
 
         const file = await this.fixPluginfileURL(siteId, fileUrl, timemodified);
+
         fileUrl = file.fileurl;
         timemodified = file.timemodified || timemodified;
         revision = revision || this.getRevisionFromUrl(fileUrl);
         const fileId = this.getFileIdByUrl(fileUrl);
 
-        return this.hasFileInPool(siteId, fileId).then(async (entry) => {
-            if (typeof entry === 'undefined') {
-                // We do not have the file, add it to the queue, and return real URL.
-                addToQueue(fileUrl);
+        try {
+            const entry = await this.hasFileInPool(siteId, fileId);
 
-                return fileUrl;
+            if (typeof entry === 'undefined') {
+                throw new CoreError('File not downloaded.');
             }
 
             if (this.isFileOutdated(entry, revision, timemodified) && CoreApp.instance.isOnline()) {
-                // The file is outdated, we add to the queue and return real URL.
-                addToQueue(fileUrl);
-
-                return fileUrl;
+                throw new CoreError('File is outdated');
             }
-
-            try {
-                // We found the file entry, now look for the file on disk.
-                if (mode === 'src') {
-                    return this.getInternalSrcById(siteId, fileId);
-                } else {
-                    return this.getInternalUrlById(siteId, fileId);
-                }
-            } catch (error) {
-                // The file is not on disk.
-                // We could not retrieve the file, delete the entries associated with that ID.
-                this.logger.debug('File ' + fileId + ' not found on disk');
-                this.removeFileById(siteId, fileId);
-                addToQueue(fileUrl);
-
-                if (CoreApp.instance.isOnline()) {
-                    // We still have a chance to serve the right content.
-                    return fileUrl;
-                }
-
-                throw new CoreError('File not found.');
-            }
-        }, () => {
-            // We do not have the file in store yet. Add to queue and return the fixed URL.
+        } catch (error) {
+            // The file is not downloaded or it's outdated. Add to queue and return the fixed URL.
             addToQueue(fileUrl);
 
             return fileUrl;
-        });
+        }
+
+        try {
+            // We found the file entry, now look for the file on disk.
+            if (mode === 'src') {
+                return await this.getInternalSrcById(siteId, fileId);
+            } else {
+                return await this.getInternalUrlById(siteId, fileId);
+            }
+        } catch (error) {
+            // The file is not on disk.
+            // We could not retrieve the file, delete the entries associated with that ID.
+            this.logger.debug('File ' + fileId + ' not found on disk');
+            this.removeFileById(siteId, fileId);
+            addToQueue(fileUrl);
+
+            return fileUrl;
+        }
     }
 
     /**
@@ -1770,7 +1885,7 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Download promise or undefined.
      */
-    getPackageDownloadPromise(siteId: string, component: string, componentId?: string | number): Promise<void> {
+    getPackageDownloadPromise(siteId: string, component: string, componentId?: string | number): Promise<void> | undefined {
         const packageId = this.getPackageId(component, componentId);
         if (this.packagesPromises[siteId] && this.packagesPromises[siteId][packageId]) {
             return this.packagesPromises[siteId][packageId];
@@ -1785,7 +1900,7 @@ export class CoreFilepoolProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @return Promise resolved with the extra data.
      */
-    getPackageExtra(siteId: string, component: string, componentId?: string | number): Promise<string> {
+    getPackageExtra(siteId: string, component: string, componentId?: string | number): Promise<string | undefined> {
         return this.getPackageData(siteId, component, componentId).then((entry) => entry.extra);
     }
 
@@ -1842,7 +1957,7 @@ export class CoreFilepoolProvider {
      * @param url URL to get the args.
      * @return The args found, undefined if not a pluginfile.
      */
-    protected getPluginFileArgs(url: string): string[] {
+    protected getPluginFileArgs(url: string): string[] | undefined {
         if (!CoreUrlUtils.instance.isPluginFileUrl(url)) {
             // Not pluginfile, return.
             return;
@@ -1868,8 +1983,12 @@ export class CoreFilepoolProvider {
      * @param onProgress Function to call on progress.
      * @return Deferred.
      */
-    protected getQueueDeferred(siteId: string, fileId: string, create: boolean = true, onProgress?: CoreFilepoolOnProgressCallback):
-            CoreFilepoolPromiseDefer {
+    protected getQueueDeferred(
+        siteId: string,
+        fileId: string,
+        create: boolean = true,
+        onProgress?: CoreFilepoolOnProgressCallback,
+    ): CoreFilepoolPromiseDefer | undefined {
         if (!this.queueDeferreds[siteId]) {
             if (!create) {
                 return;
@@ -1897,11 +2016,10 @@ export class CoreFilepoolProvider {
      * @param fileId The file ID.
      * @return On progress function, undefined if not found.
      */
-    protected getQueueOnProgress(siteId: string, fileId: string): CoreFilepoolOnProgressCallback {
+    protected getQueueOnProgress(siteId: string, fileId: string): CoreFilepoolOnProgressCallback | undefined {
         const deferred = this.getQueueDeferred(siteId, fileId, false);
-        if (deferred) {
-            return deferred.onProgress;
-        }
+
+        return deferred?.onProgress;
     }
 
     /**
@@ -1913,9 +2031,15 @@ export class CoreFilepoolProvider {
      * @param onProgress Function to call on progress.
      * @return Promise.
      */
-    protected getQueuePromise(siteId: string, fileId: string, create: boolean = true, onProgress?: CoreFilepoolOnProgressCallback):
-            Promise<void> {
-        return this.getQueueDeferred(siteId, fileId, create, onProgress).promise;
+    protected getQueuePromise(
+        siteId: string,
+        fileId: string,
+        create: boolean = true,
+        onProgress?: CoreFilepoolOnProgressCallback,
+    ): Promise<void> | undefined {
+        const deferred = this.getQueueDeferred(siteId, fileId, create, onProgress);
+
+        return deferred?.promise;
     }
 
     /**
@@ -1984,11 +2108,29 @@ export class CoreFilepoolProvider {
      * This will return a URL pointing to the content of the requested URL.
      * The URL returned is compatible to use with IMG tags.
      */
-    getSrcByUrl(siteId: string, fileUrl: string, component: string, componentId?: string | number, timemodified: number = 0,
-            checkSize: boolean = true, downloadUnknown?: boolean, options: CoreFilepoolFileOptions = {}, revision?: number):
-            Promise<string> {
-        return this.getFileUrlByUrl(siteId, fileUrl, component, componentId, 'src',
-            timemodified, checkSize, downloadUnknown, options, revision);
+    getSrcByUrl(
+        siteId: string,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified: number = 0,
+        checkSize: boolean = true,
+        downloadUnknown?: boolean,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+    ): Promise<string> {
+        return this.getFileUrlByUrl(
+            siteId,
+            fileUrl,
+            component,
+            componentId,
+            'src',
+            timemodified,
+            checkSize,
+            downloadUnknown,
+            options,
+            revision,
+        );
     }
 
     /**
@@ -2001,7 +2143,7 @@ export class CoreFilepoolProvider {
         let timemodified = 0;
 
         files.forEach((file) => {
-            if (file.timemodified > timemodified) {
+            if (file.timemodified && file.timemodified > timemodified) {
                 timemodified = file.timemodified;
             }
         });
@@ -2028,11 +2170,29 @@ export class CoreFilepoolProvider {
      * This will return a URL pointing to the content of the requested URL.
      * The URL returned is compatible to use with a local browser.
      */
-    getUrlByUrl(siteId: string, fileUrl: string, component: string, componentId?: string | number, timemodified: number = 0,
-            checkSize: boolean = true, downloadUnknown?: boolean, options: CoreFilepoolFileOptions = {}, revision?: number):
-            Promise<string> {
-        return this.getFileUrlByUrl(siteId, fileUrl, component, componentId, 'url',
-            timemodified, checkSize, downloadUnknown, options, revision);
+    getUrlByUrl(
+        siteId: string,
+        fileUrl: string,
+        component?: string,
+        componentId?: string | number,
+        timemodified: number = 0,
+        checkSize: boolean = true,
+        downloadUnknown?: boolean,
+        options: CoreFilepoolFileOptions = {},
+        revision?: number,
+    ): Promise<string> {
+        return this.getFileUrlByUrl(
+            siteId,
+            fileUrl,
+            component,
+            componentId,
+            'url',
+            timemodified,
+            checkSize,
+            downloadUnknown,
+            options,
+            revision,
+        );
     }
 
     /**
@@ -2071,7 +2231,7 @@ export class CoreFilepoolProvider {
 
         // If there are hashes in the URL, extract them.
         const index = filename.indexOf('#');
-        let hashes: string[];
+        let hashes: string[] | undefined;
 
         if (index != -1) {
             hashes = filename.split('#');
@@ -2127,7 +2287,7 @@ export class CoreFilepoolProvider {
             throw new CoreError('File not found in queue.');
         }
         // Convert the links to an object.
-        entry.linksUnserialized = <CoreFilepoolComponentLink[]> CoreTextUtils.instance.parseJSON(entry.links, []);
+        entry.linksUnserialized = <CoreFilepoolComponentLink[]> CoreTextUtils.instance.parseJSON(entry.links || '[]', []);
 
         return entry;
     }
@@ -2143,7 +2303,7 @@ export class CoreFilepoolProvider {
     async invalidateAllFiles(siteId: string, onlyUnknown: boolean = true): Promise<void> {
         const db = await CoreSites.instance.getSiteDb(siteId);
 
-        const where = onlyUnknown ? CoreFilepoolProvider.FILE_UPDATE_UNKNOWN_WHERE_CLAUSE : null;
+        const where = onlyUnknown ? CoreFilepoolProvider.FILE_UPDATE_UNKNOWN_WHERE_CLAUSE : undefined;
 
         await db.updateRecordsWhere(CoreFilepoolProvider.FILES_TABLE, { stale: 1 }, where);
     }
@@ -2179,8 +2339,12 @@ export class CoreFilepoolProvider {
      *                It is advised to set it to true to reduce the performance and data usage of the app.
      * @return Resolved when done.
      */
-    async invalidateFilesByComponent(siteId: string, component: string, componentId?: string | number, onlyUnknown: boolean = true):
-            Promise<void> {
+    async invalidateFilesByComponent(
+        siteId: string,
+        component: string,
+        componentId?: string | number,
+        onlyUnknown: boolean = true,
+    ): Promise<void> {
         const db = await CoreSites.instance.getSiteDb(siteId);
 
         const items = await this.getComponentFiles(db, component, componentId);
@@ -2223,8 +2387,13 @@ export class CoreFilepoolProvider {
      * @param revision File revision. If not defined, it will be calculated using the URL.
      * @return Promise resolved with a boolean: whether a file is downloadable.
      */
-    async isFileDownloadable(siteId: string, fileUrl: string, timemodified: number = 0, filePath?: string, revision?: number):
-            Promise<boolean> {
+    async isFileDownloadable(
+        siteId: string,
+        fileUrl: string,
+        timemodified: number = 0,
+        filePath?: string,
+        revision?: number,
+    ): Promise<boolean> {
         const state = await this.getFileStateByUrl(siteId, fileUrl, timemodified, filePath, revision);
 
         return state != CoreConstants.NOT_DOWNLOADABLE;
@@ -2253,7 +2422,9 @@ export class CoreFilepoolProvider {
      * @param Whether the file is outdated.
      */
     protected isFileOutdated(entry: CoreFilepoolFileEntry, revision?: number, timemodified?: number): boolean {
-        return !!entry.stale || revision > entry.revision || timemodified > entry.timemodified;
+        return !!entry.stale ||
+            (revision !== undefined && (entry.revision === undefined || revision > entry.revision)) ||
+            (timemodified !== undefined && (entry.timemodified === undefined || timemodified > entry.timemodified));
     }
 
     /**
@@ -2273,8 +2444,11 @@ export class CoreFilepoolProvider {
      * @param eventData The file event data.
      * @param links The links to the components.
      */
-    protected notifyFileActionToComponents(siteId: string, eventData: CoreFilepoolFileEventData,
-        links: CoreFilepoolComponentLink[]): void {
+    protected notifyFileActionToComponents(
+        siteId: string,
+        eventData: CoreFilepoolFileEventData,
+        links: CoreFilepoolComponentLink[],
+    ): void {
         links.forEach((link) => {
             const data: CoreFilepoolComponentFileEventData = Object.assign({
                 component: link.component,
@@ -2385,8 +2559,15 @@ export class CoreFilepoolProvider {
      * @param onProgress Function to call on progress.
      * @return Promise resolved when all files are downloaded.
      */
-    prefetchPackage(siteId: string, fileList: CoreWSExternalFile[], component: string, componentId?: string | number,
-            extra?: string, dirPath?: string, onProgress?: CoreFilepoolOnProgressCallback): Promise<void> {
+    prefetchPackage(
+        siteId: string,
+        fileList: CoreWSExternalFile[],
+        component: string,
+        componentId?: string | number,
+        extra?: string,
+        dirPath?: string,
+        onProgress?: CoreFilepoolOnProgressCallback,
+    ): Promise<void> {
         return this.downloadOrPrefetchPackage(siteId, fileList, true, component, componentId, extra, dirPath, onProgress);
     }
 
@@ -2397,24 +2578,17 @@ export class CoreFilepoolProvider {
      * This loops over itself to keep on processing the queue in the background.
      * The queue process is site agnostic.
      */
-    protected processQueue(): void {
-        let promise: Promise<void>;
+    protected async processQueue(): Promise<void> {
+        try {
+            if (this.queueState !== CoreFilepoolProvider.QUEUE_RUNNING) {
+                // Silently ignore, the queue is on pause.
+                throw CoreFilepoolProvider.ERR_QUEUE_ON_PAUSE;
+            } else if (!CoreFile.instance.isAvailable() || !CoreApp.instance.isOnline()) {
+                throw CoreFilepoolProvider.ERR_FS_OR_NETWORK_UNAVAILABLE;
+            }
 
-        if (this.queueState !== CoreFilepoolProvider.QUEUE_RUNNING) {
-            // Silently ignore, the queue is on pause.
-            promise = Promise.reject(CoreFilepoolProvider.ERR_QUEUE_ON_PAUSE);
-        } else if (!CoreFile.instance.isAvailable() || !CoreApp.instance.isOnline()) {
-            promise = Promise.reject(CoreFilepoolProvider.ERR_FS_OR_NETWORK_UNAVAILABLE);
-        } else {
-            promise = this.processImportantQueueItem();
-        }
-
-        promise.then(() => {
-            // All good, we schedule next execution.
-            setTimeout(() => {
-                this.processQueue();
-            }, CoreFilepoolProvider.QUEUE_PROCESS_INTERVAL);
-        }, (error) => {
+            await this.processImportantQueueItem();
+        } catch (error) {
             // We had an error, in which case we pause the processing.
             if (error === CoreFilepoolProvider.ERR_FS_OR_NETWORK_UNAVAILABLE) {
                 this.logger.debug('Filesysem or network unavailable, pausing queue processing.');
@@ -2423,7 +2597,14 @@ export class CoreFilepoolProvider {
             }
 
             this.queueState = CoreFilepoolProvider.QUEUE_PAUSED;
-        });
+
+            return;
+        }
+
+        // All good, we schedule next execution.
+        setTimeout(() => {
+            this.processQueue();
+        }, CoreFilepoolProvider.QUEUE_PROCESS_INTERVAL);
     }
 
     /**
@@ -2437,8 +2618,14 @@ export class CoreFilepoolProvider {
         let items: CoreFilepoolQueueEntry[];
 
         try {
-            items = await this.appDB.getRecords<CoreFilepoolQueueEntry>(CoreFilepoolProvider.QUEUE_TABLE, undefined,
-                'priority DESC, added ASC', undefined, 0, 1);
+            items = await this.appDB.getRecords<CoreFilepoolQueueEntry>(
+                CoreFilepoolProvider.QUEUE_TABLE,
+                undefined,
+                'priority DESC, added ASC',
+                undefined,
+                0,
+                1,
+            );
         } catch (err) {
             throw CoreFilepoolProvider.ERR_QUEUE_IS_EMPTY;
         }
@@ -2475,7 +2662,7 @@ export class CoreFilepoolProvider {
 
         this.logger.debug('Processing queue item: ' + siteId + ', ' + fileId);
 
-        let entry: CoreFilepoolFileEntry;
+        let entry: CoreFilepoolFileEntry | undefined;
 
         // Check if the file is already in pool.
         try {
@@ -2502,21 +2689,19 @@ export class CoreFilepoolProvider {
         // The file does not exist, or is stale, ... download it.
         const onProgress = this.getQueueOnProgress(siteId, fileId);
 
-        return this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress, entry).then(() => {
+        try {
+            await this.downloadForPoolByUrl(siteId, fileUrl, options, filePath, onProgress, entry);
+
             // Success, we add links and remove from queue.
-            this.addFileLinks(siteId, fileId, links).catch(() => {
-                // Ignore errors.
-            });
+            CoreUtils.instance.ignoreErrors(this.addFileLinks(siteId, fileId, links));
 
             this.treatQueueDeferred(siteId, fileId, true);
             this.notifyFileDownloaded(siteId, fileId, links);
 
             // Wait for the item to be removed from queue before resolving the promise.
             // If the item could not be removed from queue we still resolve the promise.
-            return this.removeFromQueue(siteId, fileId).catch(() => {
-                // Ignore errors.
-            });
-        }, (errorObject) => {
+            await CoreUtils.instance.ignoreErrors(this.removeFromQueue(siteId, fileId));
+        } catch (errorObject) {
             // Whoops, we have an error...
             let dropFromQueue = false;
 
@@ -2544,7 +2729,7 @@ export class CoreFilepoolProvider {
                 dropFromQueue = true;
             }
 
-            let errorMessage = null;
+            let errorMessage: string | undefined;
             // Some Android devices restrict the amount of usable storage using quotas.
             // If this quota would be exceeded by the download, it throws an exception.
             // We catch this exception here, and report a meaningful error message to the user.
@@ -2555,20 +2740,18 @@ export class CoreFilepoolProvider {
             if (dropFromQueue) {
                 this.logger.debug('Item dropped from queue due to error: ' + fileUrl, errorObject);
 
-                return this.removeFromQueue(siteId, fileId).catch(() => {
-                    // Consider this as a silent error, never reject the promise here.
-                }).then(() => {
-                    this.treatQueueDeferred(siteId, fileId, false, errorMessage);
-                    this.notifyFileDownloadError(siteId, fileId, links);
-                });
+                await CoreUtils.instance.ignoreErrors(this.removeFromQueue(siteId, fileId));
+
+                this.treatQueueDeferred(siteId, fileId, false, errorMessage);
+                this.notifyFileDownloadError(siteId, fileId, links);
             } else {
                 // We considered the file as legit but did not get it, failure.
                 this.treatQueueDeferred(siteId, fileId, false, errorMessage);
                 this.notifyFileDownloadError(siteId, fileId, links);
 
-                return Promise.reject(errorObject);
+                throw errorObject;
             }
-        });
+        }
     }
 
     /**
@@ -2596,12 +2779,12 @@ export class CoreFilepoolProvider {
         // Get the path to the file first since it relies on the file object stored in the pool.
         // Don't use getFilePath to prevent performing 2 DB requests.
         let path = this.getFilepoolFolderPath(siteId) + '/' + fileId;
-        let fileUrl: string;
+        let fileUrl: string | undefined;
 
         try {
             const entry = await this.hasFileInPool(siteId, fileId);
-            fileUrl = entry.url;
 
+            fileUrl = entry.url;
             if (entry.extension) {
                 path += '.' + entry.extension;
             }
@@ -2615,7 +2798,7 @@ export class CoreFilepoolProvider {
 
         // Get links to components to notify them after remove.
         const links = await this.getFileLinks(siteId, fileId);
-        const promises = [];
+        const promises: Promise<unknown>[] = [];
 
         // Remove entry from filepool store.
         promises.push(db.deleteRecords(CoreFilepoolProvider.FILES_TABLE, conditions));
@@ -2629,7 +2812,7 @@ export class CoreFilepoolProvider {
                 if (error && error.code == 1) {
                     // Not found, ignore error since maybe it was deleted already.
                 } else {
-                    return Promise.reject(error);
+                    throw error;
                 }
             }));
         }
@@ -2638,10 +2821,8 @@ export class CoreFilepoolProvider {
 
         this.notifyFileDeleted(siteId, fileId, links);
 
-        try {
-            await CorePluginFile.instance.fileDeleted(fileUrl, path, siteId);
-        } catch (error) {
-            // Ignore errors.
+        if (fileUrl) {
+            await CoreUtils.instance.ignoreErrors(CorePluginFile.instance.fileDeleted(fileUrl, path, siteId));
         }
     }
 
@@ -2720,7 +2901,7 @@ export class CoreFilepoolProvider {
 
         await site.getDb().updateRecords(CoreFilepoolProvider.PACKAGES_TABLE, newData, { id: packageId });
         // Success updating, trigger event.
-        this.triggerPackageStatusChanged(site.id, newData.status, component, componentId);
+        this.triggerPackageStatusChanged(site.id!, newData.status, component, componentId);
 
         return newData.status;
     }
@@ -2778,22 +2959,27 @@ export class CoreFilepoolProvider {
      * @param extra Extra data to store for the package. If you want to store more than 1 value, use JSON.stringify.
      * @return Promise resolved when status is stored.
      */
-    async storePackageStatus(siteId: string, status: string, component: string, componentId?: string | number, extra?: string):
-            Promise<void> {
+    async storePackageStatus(
+        siteId: string,
+        status: string,
+        component: string,
+        componentId?: string | number,
+        extra?: string,
+    ): Promise<void> {
         this.logger.debug(`Set status '${status}' for package ${component} ${componentId}`);
         componentId = this.fixComponentId(componentId);
 
         const site = await CoreSites.instance.getSite(siteId);
         const packageId = this.getPackageId(component, componentId);
-        let downloadTime: number;
-        let previousDownloadTime: number;
+        let downloadTime: number | undefined;
+        let previousDownloadTime: number | undefined;
 
         if (status == CoreConstants.DOWNLOADING) {
             // Set download time if package is now downloading.
             downloadTime = CoreTimeUtils.instance.timestamp();
         }
 
-        let previousStatus: string;
+        let previousStatus: string | undefined;
         // Search current status to set it as previous status.
         try {
             const entry = <CoreFilepoolPackageEntry> site.getDb().getRecord(CoreFilepoolProvider.PACKAGES_TABLE, { id: packageId });
@@ -2849,40 +3035,56 @@ export class CoreFilepoolProvider {
      * @param revision Revision to use in all files. If not defined, it will be calculated using the URL of each file.
      * @return Promise resolved with the CSS code.
      */
-    treatCSSCode(siteId: string, fileUrl: string, cssCode: string, component?: string, componentId?: string | number,
-        revision?: number): Promise<string> {
+    async treatCSSCode(
+        siteId: string,
+        fileUrl: string,
+        cssCode: string,
+        component?: string,
+        componentId?: string | number,
+        revision?: number,
+    ): Promise<string> {
         const urls = CoreDomUtils.instance.extractUrlsFromCSS(cssCode);
-        const promises = [];
-        let filePath: string;
         let updated = false;
 
         // Get the path of the CSS file.
-        promises.push(this.getFilePathByUrl(siteId, fileUrl).then((path) => {
-            filePath = path;
+        const filePath = await this.getFilePathByUrl(siteId, fileUrl);
+
+        // Download all files in the CSS.
+        await Promise.all(urls.map(async (url) => {
+            // Download the file only if it's an online URL.
+            if (CoreUrlUtils.instance.isLocalFileUrl(url)) {
+                return;
+            }
+
+            try {
+                const fileUrl = await this.downloadUrl(
+                    siteId,
+                    url,
+                    false,
+                    component,
+                    componentId,
+                    0,
+                    undefined,
+                    undefined,
+                    undefined,
+                    revision,
+                );
+
+                if (fileUrl != url) {
+                    cssCode = cssCode.replace(new RegExp(CoreTextUtils.instance.escapeForRegex(url), 'g'), fileUrl);
+                    updated = true;
+                }
+            } catch (error) {
+                this.logger.warn('Error treating file ', url, error);
+            }
         }));
 
-        urls.forEach((url) => {
-            // Download the file only if it's an online URL.
-            if (!CoreUrlUtils.instance.isLocalFileUrl(url)) {
-                promises.push(this.downloadUrl(siteId, url, false, component, componentId, 0, undefined, undefined, undefined,
-                    revision).then((fileUrl) => {
-                    if (fileUrl != url) {
-                        cssCode = cssCode.replace(new RegExp(CoreTextUtils.instance.escapeForRegex(url), 'g'), fileUrl);
-                        updated = true;
-                    }
-                }).catch((error) => {
-                    // It shouldn't happen. Ignore errors.
-                    this.logger.warn('Error treating file ', url, error);
-                }));
-            }
-        });
+        // All files downloaded. Store the result if it has changed.
+        if (updated) {
+            await CoreFile.instance.writeFile(filePath, cssCode);
+        }
 
-        return Promise.all(promises).then(() => {
-            // All files downloaded. Store the result if it has changed.
-            if (updated) {
-                return CoreFile.instance.writeFile(filePath, cssCode);
-            }
-        }).then(() => cssCode);
+        return cssCode;
     }
 
     /**
@@ -2912,7 +3114,7 @@ export class CoreFilepoolProvider {
      * @param component Package's component.
      * @param componentId An ID to use in conjunction with the component.
      */
-    protected triggerPackageStatusChanged(siteId: string, status: string, component: string, componentId?: string | number): void {
+    protected triggerPackageStatusChanged(siteId: string, status: string, component?: string, componentId?: string | number): void {
         const data = {
             component,
             componentId: this.fixComponentId(componentId),
@@ -2938,8 +3140,11 @@ export class CoreFilepoolProvider {
         const site = await CoreSites.instance.getSite(siteId);
         const packageId = this.getPackageId(component, componentId);
 
-        await site.getDb().updateRecords(CoreFilepoolProvider.PACKAGES_TABLE,
-            { downloadTime: CoreTimeUtils.instance.timestamp() }, { id: packageId });
+        await site.getDb().updateRecords(
+            CoreFilepoolProvider.PACKAGES_TABLE,
+            { downloadTime: CoreTimeUtils.instance.timestamp() },
+            { id: packageId },
+        );
     }
 
 }
@@ -2963,32 +3168,32 @@ export type CoreFilepoolFileEntry = CoreFilepoolFileOptions & {
     /**
      * The fileId to identify the file.
      */
-    fileId?: string;
+    fileId: string;
 
     /**
      * File's URL.
      */
-    url?: string;
+    url: string;
 
     /**
      * 1 if file is stale (needs to be updated), 0 otherwise.
      */
-    stale?: number;
+    stale: number;
 
     /**
      * Timestamp when this file was downloaded.
      */
-    downloadTime?: number;
+    downloadTime: number;
 
     /**
      * File's path.
      */
-    path?: string;
+    path: string;
 
     /**
      * File's extension.
      */
-    extension?: string;
+    extension: string;
 };
 
 /**
@@ -2998,27 +3203,27 @@ export type CoreFilepoolQueueDBEntry = CoreFilepoolFileOptions & {
     /**
      * The site the file belongs to.
      */
-    siteId?: string;
+    siteId: string;
 
     /**
      * The fileId to identify the file.
      */
-    fileId?: string;
+    fileId: string;
 
     /**
      * Timestamp when the file was added to the queue.
      */
-    added?: number;
+    added: number;
 
     /**
      * The priority of the file.
      */
-    priority?: number;
+    priority: number;
 
     /**
      * File's URL.
      */
-    url?: string;
+    url: string;
 
     /**
      * File's path.
@@ -3028,7 +3233,7 @@ export type CoreFilepoolQueueDBEntry = CoreFilepoolFileOptions & {
     /**
      * File links (to link the file to components and componentIds). Serialized to store on DB.
      */
-    links?: string;
+    links: string;
 };
 
 /**
@@ -3148,7 +3353,7 @@ export type CoreFilepoolComponentFileEventData = CoreFilepoolFileEventData & {
     /**
      * The component ID.
      */
-    componentId: string | number;
+    componentId?: string | number;
 };
 
 /**
@@ -3171,3 +3376,6 @@ type CoreFilepoolLinksRecord = {
     component: string; // Component name.
     componentId: number | string; // Component Id.
 };
+
+type AnchorOrMediaElement =
+    HTMLAnchorElement | HTMLImageElement | HTMLAudioElement | HTMLVideoElement | HTMLSourceElement | HTMLTrackElement;
diff --git a/src/app/services/local-notifications.ts b/src/app/services/local-notifications.ts
index 385837a89..9c2175d44 100644
--- a/src/app/services/local-notifications.ts
+++ b/src/app/services/local-notifications.ts
@@ -106,7 +106,7 @@ export class CoreLocalNotificationsProvider {
     protected cancelSubscription?: Subscription;
     protected addSubscription?: Subscription;
     protected updateSubscription?: Subscription;
-    protected queueRunner?: CoreQueueRunner; // Queue to decrease the number of concurrent calls to the plugin (see MOBILE-3477).
+    protected queueRunner: CoreQueueRunner; // Queue to decrease the number of concurrent calls to the plugin (see MOBILE-3477).
 
     constructor() {
         this.logger = CoreLogger.getInstance('CoreLocalNotificationsProvider');
@@ -116,46 +116,53 @@ export class CoreLocalNotificationsProvider {
             // Ignore errors.
         });
 
-        Platform.instance.ready().then(() => {
-            // Listen to events.
-            this.triggerSubscription = LocalNotifications.instance.on('trigger').subscribe((notification: ILocalNotification) => {
-                this.trigger(notification);
+        this.init();
+    }
 
-                this.handleEvent('trigger', notification);
-            });
+    /**
+     * Init some properties.
+     */
+    protected async init(): Promise<void> {
+        await Platform.instance.ready();
 
-            this.clickSubscription = LocalNotifications.instance.on('click').subscribe((notification: ILocalNotification) => {
-                this.handleEvent('click', notification);
-            });
+        // Listen to events.
+        this.triggerSubscription = LocalNotifications.instance.on('trigger').subscribe((notification: ILocalNotification) => {
+            this.trigger(notification);
 
-            this.clearSubscription = LocalNotifications.instance.on('clear').subscribe((notification: ILocalNotification) => {
-                this.handleEvent('clear', notification);
-            });
+            this.handleEvent('trigger', notification);
+        });
 
-            this.cancelSubscription = LocalNotifications.instance.on('cancel').subscribe((notification: ILocalNotification) => {
-                this.handleEvent('cancel', notification);
-            });
+        this.clickSubscription = LocalNotifications.instance.on('click').subscribe((notification: ILocalNotification) => {
+            this.handleEvent('click', notification);
+        });
 
-            this.addSubscription = LocalNotifications.instance.on('schedule').subscribe((notification: ILocalNotification) => {
-                this.handleEvent('schedule', notification);
-            });
+        this.clearSubscription = LocalNotifications.instance.on('clear').subscribe((notification: ILocalNotification) => {
+            this.handleEvent('clear', notification);
+        });
 
-            this.updateSubscription = LocalNotifications.instance.on('update').subscribe((notification: ILocalNotification) => {
-                this.handleEvent('update', notification);
-            });
+        this.cancelSubscription = LocalNotifications.instance.on('cancel').subscribe((notification: ILocalNotification) => {
+            this.handleEvent('cancel', notification);
+        });
 
-            // Create the default channel for local notifications.
+        this.addSubscription = LocalNotifications.instance.on('schedule').subscribe((notification: ILocalNotification) => {
+            this.handleEvent('schedule', notification);
+        });
+
+        this.updateSubscription = LocalNotifications.instance.on('update').subscribe((notification: ILocalNotification) => {
+            this.handleEvent('update', notification);
+        });
+
+        // Create the default channel for local notifications.
+        this.createDefaultChannel();
+
+        Translate.instance.onLangChange.subscribe(() => {
+            // Update the channel name.
             this.createDefaultChannel();
-
-            Translate.instance.onLangChange.subscribe(() => {
-                // Update the channel name.
-                this.createDefaultChannel();
-            });
         });
 
         CoreEvents.instance.on(CoreEventsProvider.SITE_DELETED, (site: CoreSite) => {
             if (site) {
-                this.cancelSiteNotifications(site.id);
+                this.cancelSiteNotifications(site.id!);
             }
         });
     }
@@ -193,13 +200,13 @@ export class CoreLocalNotificationsProvider {
 
         const scheduled = await this.getAllScheduled();
 
-        const ids = [];
+        const ids: number[] = [];
         const queueId = 'cancelSiteNotifications-' + siteId;
 
         scheduled.forEach((notif) => {
             notif.data = this.parseNotificationData(notif.data);
 
-            if (typeof notif.data == 'object' && notif.data.siteId === siteId) {
+            if (notif.id && typeof notif.data == 'object' && notif.data.siteId === siteId) {
                 ids.push(notif.id);
             }
         });
@@ -355,10 +362,9 @@ export class CoreLocalNotificationsProvider {
      * @return Whether local notifications plugin is installed.
      */
     isAvailable(): boolean {
-        const win = <any> window;
+        const win = <any> window; // eslint-disable-line @typescript-eslint/no-explicit-any
 
-        return CoreApp.instance.isDesktop() || !!(win.cordova && win.cordova.plugins && win.cordova.plugins.notification &&
-                win.cordova.plugins.notification.local);
+        return CoreApp.instance.isDesktop() || !!win.cordova?.plugins?.notification?.local;
     }
 
     /**
@@ -388,11 +394,11 @@ export class CoreLocalNotificationsProvider {
             if (useQueue) {
                 const queueId = 'isTriggered-' + notification.id;
 
-                return this.queueRunner.run(queueId, () => LocalNotifications.instance.isTriggered(notification.id), {
+                return this.queueRunner.run(queueId, () => LocalNotifications.instance.isTriggered(notification.id!), {
                     allowRepeated: true,
                 });
             } else {
-                return LocalNotifications.instance.isTriggered(notification.id);
+                return LocalNotifications.instance.isTriggered(notification.id || 0);
             }
         }
     }
@@ -446,9 +452,8 @@ export class CoreLocalNotificationsProvider {
     /**
      * Process the next request in queue.
      */
-    protected processNextRequest(): void {
+    protected async processNextRequest(): Promise<void> {
         const nextKey = Object.keys(this.codeRequestsQueue)[0];
-        let promise: Promise<void>;
 
         if (typeof nextKey == 'undefined') {
             // No more requests in queue, stop.
@@ -457,27 +462,27 @@ export class CoreLocalNotificationsProvider {
 
         const request = this.codeRequestsQueue[nextKey];
 
-        // Check if request is valid.
-        if (typeof request == 'object' && typeof request.table != 'undefined' && typeof request.id != 'undefined') {
-            // Get the code and resolve/reject all the promises of this request.
-            promise = this.getCode(request.table, request.id).then((code) => {
-                request.deferreds.forEach((p) => {
-                    p.resolve(code);
-                });
-            }).catch((error) => {
-                request.deferreds.forEach((p) => {
-                    p.reject(error);
-                });
-            });
-        } else {
-            promise = Promise.resolve();
-        }
+        try {
+            // Check if request is valid.
+            if (typeof request != 'object' || request.table === undefined || request.id === undefined) {
+                return;
+            }
 
-        // Once this item is treated, remove it and process next.
-        promise.finally(() => {
+            // Get the code and resolve/reject all the promises of this request.
+            const code = await this.getCode(request.table, request.id);
+
+            request.deferreds.forEach((p) => {
+                p.resolve(code);
+            });
+        } catch (error) {
+            request.deferreds.forEach((p) => {
+                p.reject(error);
+            });
+        } finally {
+            // Once this item is treated, remove it and process next.
             delete this.codeRequestsQueue[nextKey];
             this.processNextRequest();
-        });
+        }
     }
 
     /**
@@ -596,7 +601,7 @@ export class CoreLocalNotificationsProvider {
      */
     async schedule(notification: ILocalNotification, component: string, siteId: string, alreadyUnique?: boolean): Promise<void> {
         if (!alreadyUnique) {
-            notification.id = await this.getUniqueNotificationId(notification.id, component, siteId);
+            notification.id = await this.getUniqueNotificationId(notification.id || 0, component, siteId);
         }
 
         notification.data = notification.data || {};
@@ -663,7 +668,7 @@ export class CoreLocalNotificationsProvider {
                 }
 
                 if (!soundEnabled) {
-                    notification.sound = null;
+                    notification.sound = undefined;
                 } else {
                     delete notification.sound; // Use default value.
                 }
@@ -671,7 +676,7 @@ export class CoreLocalNotificationsProvider {
                 notification.foreground = true;
 
                 // Remove from triggered, since the notification could be in there with a different time.
-                this.removeTriggered(notification.id);
+                this.removeTriggered(notification.id || 0);
                 LocalNotifications.instance.schedule(notification);
             }
         });
diff --git a/src/app/services/plugin-file-delegate.ts b/src/app/services/plugin-file-delegate.ts
index 8621d13b8..572cc0913 100644
--- a/src/app/services/plugin-file-delegate.ts
+++ b/src/app/services/plugin-file-delegate.ts
@@ -206,7 +206,7 @@ export class CorePluginFileDelegate extends CoreDelegate {
             }
         }
 
-        return downloadableFile.filesize;
+        return downloadableFile.filesize || 0;
     }
 
     /**
@@ -215,7 +215,7 @@ export class CorePluginFileDelegate extends CoreDelegate {
      * @param file File data.
      * @return Handler.
      */
-    protected getHandlerForFile(file: CoreWSExternalFile): CorePluginFileHandler {
+    protected getHandlerForFile(file: CoreWSExternalFile): CorePluginFileHandler | undefined {
         for (const component in this.enabledHandlers) {
             const handler = <CorePluginFileHandler> this.enabledHandlers[component];
 
diff --git a/src/app/services/sites.ts b/src/app/services/sites.ts
index 004be6ac3..923803668 100644
--- a/src/app/services/sites.ts
+++ b/src/app/services/sites.ts
@@ -130,7 +130,7 @@ export class CoreSitesProvider {
 
                     // Move the records from the old table.
                     const sites = await db.getAllRecords<SiteDBEntry>(oldTable);
-                    const promises = [];
+                    const promises: Promise<number>[] = [];
 
                     sites.forEach((site) => {
                         promises.push(db.insertRecord(newTable, site));
@@ -153,12 +153,12 @@ export class CoreSitesProvider {
     protected readonly VALID_VERSION = 1;
     protected readonly INVALID_VERSION = -1;
 
-    protected isWPApp: boolean;
+    protected isWPApp = false;
 
     protected logger: CoreLogger;
     protected services = {};
     protected sessionRestored = false;
-    protected currentSite: CoreSite;
+    protected currentSite?: CoreSite;
     protected sites: { [s: string]: CoreSite } = {};
     protected appDB: SQLiteDB;
     protected dbReady: Promise<void>; // Promise resolved when the app DB is initialized.
@@ -249,7 +249,8 @@ export class CoreSitesProvider {
                 await db.execute(
                     'INSERT INTO ' + newTable + ' ' +
                     'SELECT id, data, key, expirationTime, NULL as component, NULL as componentId ' +
-                    'FROM ' + oldTable);
+                    'FROM ' + oldTable,
+                );
 
                 try {
                     await db.dropTable(oldTable);
@@ -276,7 +277,7 @@ export class CoreSitesProvider {
      * @param name Name of the site to check.
      * @return Site data if it's a demo site, undefined otherwise.
      */
-    getDemoSiteData(name: string): CoreSitesDemoSiteData {
+    getDemoSiteData(name: string): CoreSitesDemoSiteData | undefined {
         const demoSites = CoreConfigConstants.demo_sites;
         name = name.toLowerCase();
 
@@ -293,39 +294,43 @@ export class CoreSitesProvider {
      * @param protocol Protocol to use first.
      * @return A promise resolved when the site is checked.
      */
-    checkSite(siteUrl: string, protocol: string = 'https://'): Promise<CoreSiteCheckResponse> {
+    async checkSite(siteUrl: string, protocol: string = 'https://'): Promise<CoreSiteCheckResponse> {
         // The formatURL function adds the protocol if is missing.
         siteUrl = CoreUrlUtils.instance.formatURL(siteUrl);
 
         if (!CoreUrlUtils.instance.isHttpURL(siteUrl)) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.login.invalidsite')));
+            throw new CoreError(Translate.instance.instant('core.login.invalidsite'));
         } else if (!CoreApp.instance.isOnline()) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.networkerrormsg')));
-        } else {
-            return this.checkSiteWithProtocol(siteUrl, protocol).catch((error: CoreSiteError) => {
-                // Do not continue checking if a critical error happened.
-                if (error.critical) {
-                    return Promise.reject(error);
+            throw new CoreError(Translate.instance.instant('core.networkerrormsg'));
+        }
+
+        try {
+            return await this.checkSiteWithProtocol(siteUrl, protocol);
+        } catch (error) {
+            // Do not continue checking if a critical error happened.
+            if (error.critical) {
+                throw error;
+            }
+
+            // Retry with the other protocol.
+            protocol = protocol == 'https://' ? 'http://' : 'https://';
+
+            try {
+                return await this.checkSiteWithProtocol(siteUrl, protocol);
+            } catch (secondError) {
+                if (secondError.critical) {
+                    throw secondError;
                 }
 
-                // Retry with the other protocol.
-                protocol = protocol == 'https://' ? 'http://' : 'https://';
-
-                return this.checkSiteWithProtocol(siteUrl, protocol).catch((secondError: CoreSiteError) => {
-                    if (secondError.critical) {
-                        return Promise.reject(secondError);
-                    }
-
-                    // Site doesn't exist. Return the error message.
-                    if (CoreTextUtils.instance.getErrorMessageFromError(error)) {
-                        return Promise.reject(error);
-                    } else if (CoreTextUtils.instance.getErrorMessageFromError(secondError)) {
-                        return Promise.reject(secondError);
-                    } else {
-                        return Translate.instance.instant('core.cannotconnecttrouble');
-                    }
-                });
-            });
+                // Site doesn't exist. Return the error message.
+                if (CoreTextUtils.instance.getErrorMessageFromError(error)) {
+                    throw error;
+                } else if (CoreTextUtils.instance.getErrorMessageFromError(secondError)) {
+                    throw secondError;
+                } else {
+                    throw new CoreError(Translate.instance.instant('core.cannotconnecttrouble'));
+                }
+            }
         }
     }
 
@@ -336,121 +341,123 @@ export class CoreSitesProvider {
      * @param protocol Protocol to use.
      * @return A promise resolved when the site is checked.
      */
-    checkSiteWithProtocol(siteUrl: string, protocol: string): Promise<CoreSiteCheckResponse> {
-        let publicConfig: CoreSitePublicConfigResponse;
+    async checkSiteWithProtocol(siteUrl: string, protocol: string): Promise<CoreSiteCheckResponse> {
+        let publicConfig: CoreSitePublicConfigResponse | undefined;
 
         // Now, replace the siteUrl with the protocol.
         siteUrl = siteUrl.replace(/^https?:\/\//i, protocol);
 
-        return this.siteExists(siteUrl).catch((error: CoreSiteError) => {
+        try {
+            await this.siteExists(siteUrl);
+        } catch (error) {
             // Do not continue checking if WS are not enabled.
             if (error.errorcode == 'enablewsdescription') {
                 error.critical = true;
 
-                return Promise.reject(error);
+                throw error;
             }
 
             // Site doesn't exist. Try to add or remove 'www'.
             const treatedUrl = CoreUrlUtils.instance.addOrRemoveWWW(siteUrl);
 
-            return this.siteExists(treatedUrl).then(() => {
+            try {
+                await this.siteExists(treatedUrl);
+
                 // Success, use this new URL as site url.
                 siteUrl = treatedUrl;
-            }).catch((secondError: CoreSiteError) => {
+            } catch (secondError) {
                 // Do not continue checking if WS are not enabled.
                 if (secondError.errorcode == 'enablewsdescription') {
                     secondError.critical = true;
 
-                    return Promise.reject(secondError);
+                    throw secondError;
                 }
 
                 // Return the error.
                 if (CoreTextUtils.instance.getErrorMessageFromError(error)) {
-                    return Promise.reject(error);
+                    throw error;
                 } else {
-                    return Promise.reject(secondError);
+                    throw secondError;
                 }
+            }
+        }
+
+        // Site exists. Create a temporary site to check if local_mobile is installed.
+        const temporarySite = new CoreSite(undefined, siteUrl);
+        let data: LocalMobileResponse;
+
+        try {
+            data = await temporarySite.checkLocalMobilePlugin();
+        } catch (error) {
+            // Local mobile check returned an error. This only happens if the plugin is installed and it returns an error.
+            throw new CoreSiteError({
+                message: error.message,
+                critical: true,
             });
-        }).then(() => {
-            // Create a temporary site to check if local_mobile is installed.
-            const temporarySite = new CoreSite(undefined, siteUrl);
+        }
 
-            return temporarySite.checkLocalMobilePlugin().then((data) => {
-                data.service = data.service || CoreConfigConstants.wsservice;
-                this.services[siteUrl] = data.service; // No need to store it in DB.
+        data.service = data.service || CoreConfigConstants.wsservice;
+        this.services[siteUrl] = data.service; // No need to store it in DB.
 
-                if (data.coreSupported ||
-                    (data.code != CoreConstants.LOGIN_SSO_CODE && data.code != CoreConstants.LOGIN_SSO_INAPP_CODE)) {
-                    // SSO using local_mobile not needed, try to get the site public config.
-                    return temporarySite.getPublicConfig().then((config) => {
-                        publicConfig = config;
+        if (data.coreSupported || (data.code != CoreConstants.LOGIN_SSO_CODE && data.code != CoreConstants.LOGIN_SSO_INAPP_CODE)) {
+            // SSO using local_mobile not needed, try to get the site public config.
+            try {
+                const config = await temporarySite.getPublicConfig();
 
-                        // Check that the user can authenticate.
-                        if (!config.enablewebservices) {
-                            return Promise.reject(new CoreSiteError({
-                                message: Translate.instance.instant('core.login.webservicesnotenabled'),
-                            }));
-                        } else if (!config.enablemobilewebservice) {
-                            return Promise.reject(new CoreSiteError({
-                                message: Translate.instance.instant('core.login.mobileservicesnotenabled'),
-                            }));
-                        } else if (config.maintenanceenabled) {
-                            let message = Translate.instance.instant('core.sitemaintenance');
-                            if (config.maintenancemessage) {
-                                message += config.maintenancemessage;
-                            }
+                publicConfig = config;
 
-                            return Promise.reject(new CoreSiteError({
-                                message,
-                            }));
-                        }
+                // Check that the user can authenticate.
+                if (!config.enablewebservices) {
+                    throw new CoreSiteError({
+                        message: Translate.instance.instant('core.login.webservicesnotenabled'),
+                    });
+                } else if (!config.enablemobilewebservice) {
+                    throw new CoreSiteError({
+                        message: Translate.instance.instant('core.login.mobileservicesnotenabled'),
+                    });
+                } else if (config.maintenanceenabled) {
+                    let message = Translate.instance.instant('core.sitemaintenance');
+                    if (config.maintenancemessage) {
+                        message += config.maintenancemessage;
+                    }
 
-                        // Everything ok.
-                        if (data.code === 0) {
-                            data.code = config.typeoflogin;
-                        }
-
-                        return data;
-                    }, async (error) => {
-                        // Error, check if not supported.
-                        if (error.available === 1) {
-                            // Service supported but an error happened. Return error.
-                            if (error.errorcode == 'codingerror') {
-                                // This could be caused by a redirect. Check if it's the case.
-                                const redirect = await CoreUtils.instance.checkRedirect(siteUrl);
-
-                                if (redirect) {
-                                    error.error = Translate.instance.instant('core.login.sitehasredirect');
-                                } else {
-                                    // We can't be sure if there is a redirect or not. Display cannot connect error.
-                                    error.error = Translate.instance.instant('core.cannotconnecttrouble');
-                                }
-                            }
-
-                            return Promise.reject(new CoreSiteError({
-                                message: error.error,
-                                errorcode: error.errorcode,
-                                critical: true,
-                            }));
-                        }
-
-                        return data;
+                    throw new CoreSiteError({
+                        message,
                     });
                 }
 
-                return data;
-            }, (error: CoreError) =>
-                // Local mobile check returned an error. This only happens if the plugin is installed and it returns an error.
-                Promise.reject(new CoreSiteError({
-                    message: error.message,
-                    critical: true,
-                })),
-            ).then((data: LocalMobileResponse) => {
-                siteUrl = temporarySite.getURL();
+                // Everything ok.
+                if (data.code === 0) {
+                    data.code = config.typeoflogin;
+                }
+            } catch (error) {
+                // Error, check if not supported.
+                if (error.available === 1) {
+                    // Service supported but an error happened. Return error.
+                    if (error.errorcode == 'codingerror') {
+                        // This could be caused by a redirect. Check if it's the case.
+                        const redirect = await CoreUtils.instance.checkRedirect(siteUrl);
 
-                return { siteUrl, code: data.code, warning: data.warning, service: data.service, config: publicConfig };
-            });
-        });
+                        if (redirect) {
+                            error.error = Translate.instance.instant('core.login.sitehasredirect');
+                        } else {
+                            // We can't be sure if there is a redirect or not. Display cannot connect error.
+                            error.error = Translate.instance.instant('core.cannotconnecttrouble');
+                        }
+                    }
+
+                    throw new CoreSiteError({
+                        message: error.error,
+                        errorcode: error.errorcode,
+                        critical: true,
+                    });
+                }
+            }
+        }
+
+        siteUrl = temporarySite.getURL();
+
+        return { siteUrl, code: data.code, warning: data.warning, service: data.service, config: publicConfig };
     }
 
     /**
@@ -482,7 +489,7 @@ export class CoreSitesProvider {
         if (data.errorcode && (data.errorcode == 'enablewsdescription' || data.errorcode == 'requirecorrectaccess')) {
             throw new CoreSiteError({
                 errorcode: data.errorcode,
-                message: data.error,
+                message: data.error!,
             });
         }
 
@@ -506,10 +513,15 @@ export class CoreSitesProvider {
      * @param retry Whether we are retrying with a prefixed URL.
      * @return A promise resolved when the token is retrieved.
      */
-    getUserToken(siteUrl: string, username: string, password: string, service?: string, retry?: boolean):
-            Promise<CoreSiteUserTokenResponse> {
+    async getUserToken(
+        siteUrl: string,
+        username: string,
+        password: string,
+        service?: string,
+        retry?: boolean,
+    ): Promise<CoreSiteUserTokenResponse> {
         if (!CoreApp.instance.isOnline()) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.networkerrormsg')));
+            throw new CoreError(Translate.instance.instant('core.networkerrormsg'));
         }
 
         if (!service) {
@@ -522,47 +534,46 @@ export class CoreSitesProvider {
             service,
         };
         const loginUrl = siteUrl + '/login/token.php';
-        const promise = Http.instance.post(loginUrl, params).pipe(timeout(CoreWS.instance.getRequestTimeout())).toPromise();
+        let data: CoreSitesLoginTokenResponse;
 
-        return promise.then((data: CoreSitesLoginTokenResponse) => {
-            if (typeof data == 'undefined') {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.cannotconnecttrouble')));
+        try {
+            data = await Http.instance.post(loginUrl, params).pipe(timeout(CoreWS.instance.getRequestTimeout())).toPromise();
+        } catch (error) {
+            throw new CoreError(Translate.instance.instant('core.cannotconnecttrouble'));
+        }
+
+        if (typeof data == 'undefined') {
+            throw new CoreError(Translate.instance.instant('core.cannotconnecttrouble'));
+        } else {
+            if (typeof data.token != 'undefined') {
+                return { token: data.token, siteUrl, privateToken: data.privatetoken };
             } else {
-                if (typeof data.token != 'undefined') {
-                    return { token: data.token, siteUrl, privateToken: data.privatetoken };
-                } else {
-                    if (typeof data.error != 'undefined') {
-                        // We only allow one retry (to avoid loops).
-                        if (!retry && data.errorcode == 'requirecorrectaccess') {
-                            siteUrl = CoreUrlUtils.instance.addOrRemoveWWW(siteUrl);
+                if (typeof data.error != 'undefined') {
+                    // We only allow one retry (to avoid loops).
+                    if (!retry && data.errorcode == 'requirecorrectaccess') {
+                        siteUrl = CoreUrlUtils.instance.addOrRemoveWWW(siteUrl);
 
-                            return this.getUserToken(siteUrl, username, password, service, true);
-                        } else if (data.errorcode == 'missingparam') {
-                            // It seems the server didn't receive all required params, it could be due to a redirect.
-                            return CoreUtils.instance.checkRedirect(loginUrl).then((redirect) => {
-                                if (redirect) {
-                                    return Promise.reject(new CoreSiteError({
-                                        message: Translate.instance.instant('core.login.sitehasredirect'),
-                                    }));
-                                } else {
-                                    return Promise.reject(new CoreSiteError({
-                                        message: data.error,
-                                        errorcode: data.errorcode,
-                                    }));
-                                }
+                        return this.getUserToken(siteUrl, username, password, service, true);
+                    } else if (data.errorcode == 'missingparam') {
+                        // It seems the server didn't receive all required params, it could be due to a redirect.
+                        const redirect = await CoreUtils.instance.checkRedirect(loginUrl);
+
+                        if (redirect) {
+                            throw new CoreSiteError({
+                                message: Translate.instance.instant('core.login.sitehasredirect'),
                             });
-                        } else {
-                            return Promise.reject(new CoreSiteError({
-                                message: data.error,
-                                errorcode: data.errorcode,
-                            }));
                         }
-                    } else {
-                        return Promise.reject(new CoreError(Translate.instance.instant('core.login.invalidaccount')));
                     }
+
+                    throw new CoreSiteError({
+                        message: data.error,
+                        errorcode: data.errorcode,
+                    });
                 }
+
+                throw new CoreError(Translate.instance.instant('core.login.invalidaccount'));
             }
-        }, () => Promise.reject(new CoreError(Translate.instance.instant('core.cannotconnecttrouble'))));
+        }
     }
 
     /**
@@ -575,7 +586,13 @@ export class CoreSitesProvider {
      * @param oauthId OAuth ID. Only if the authentication was using an OAuth method.
      * @return A promise resolved with siteId when the site is added and the user is authenticated.
      */
-    newSite(siteUrl: string, token: string, privateToken: string = '', login: boolean = true, oauthId?: number): Promise<string> {
+    async newSite(
+        siteUrl: string,
+        token: string,
+        privateToken: string = '',
+        login: boolean = true,
+        oauthId?: number,
+    ): Promise<string> {
         if (typeof login != 'boolean') {
             login = true;
         }
@@ -584,74 +601,77 @@ export class CoreSitesProvider {
         let candidateSite = new CoreSite(undefined, siteUrl, token, undefined, privateToken, undefined, undefined);
         let isNewSite = true;
 
-        return candidateSite.fetchSiteInfo().then((info) => {
+        try {
+            const info = await candidateSite.fetchSiteInfo();
+
             const result = this.isValidMoodleVersion(info);
-            if (result == this.VALID_VERSION) {
-                const siteId = this.createSiteID(info.siteurl, info.username);
-
-                // Check if the site already exists.
-                return this.getSite(siteId).catch(() => {
-                    // Not exists.
-                }).then((site) => {
-                    if (site) {
-                        // Site already exists, update its data and use it.
-                        isNewSite = false;
-                        candidateSite = site;
-                        candidateSite.setToken(token);
-                        candidateSite.setPrivateToken(privateToken);
-                        candidateSite.setInfo(info);
-                        candidateSite.setOAuthId(oauthId);
-                        candidateSite.setLoggedOut(false);
-                    } else {
-                        // New site, set site ID and info.
-                        isNewSite = true;
-                        candidateSite.setId(siteId);
-                        candidateSite.setInfo(info);
-                        candidateSite.setOAuthId(oauthId);
-
-                        // Create database tables before login and before any WS call.
-                        return this.migrateSiteSchemas(candidateSite);
-                    }
-                }).then(() =>
-
-                    // Try to get the site config.
-                    this.getSiteConfig(candidateSite).catch((error) => {
-                        // Ignore errors if it's not a new site, we'll use the config already stored.
-                        if (isNewSite) {
-                            return Promise.reject(error);
-                        }
-                    }).then((config) => {
-                        if (typeof config != 'undefined') {
-                            candidateSite.setConfig(config);
-                        }
-
-                        // Add site to sites list.
-                        this.addSite(siteId, siteUrl, token, info, privateToken, config, oauthId);
-                        this.sites[siteId] = candidateSite;
-
-                        if (login) {
-                            // Turn candidate site into current site.
-                            this.currentSite = candidateSite;
-                            // Store session.
-                            this.login(siteId);
-                        }
-
-                        CoreEvents.instance.trigger(CoreEventsProvider.SITE_ADDED, info, siteId);
-
-                        return siteId;
-                    }),
-                );
+            if (result != this.VALID_VERSION) {
+                return this.treatInvalidAppVersion(result, siteUrl);
             }
 
-            return this.treatInvalidAppVersion(result, siteUrl);
-        }).catch((error) => {
+            const siteId = this.createSiteID(info.siteurl, info.username);
+
+            // Check if the site already exists.
+            const site = await CoreUtils.instance.ignoreErrors<CoreSite>(this.getSite(siteId));
+
+            if (site) {
+                // Site already exists, update its data and use it.
+                isNewSite = false;
+                candidateSite = site;
+                candidateSite.setToken(token);
+                candidateSite.setPrivateToken(privateToken);
+                candidateSite.setInfo(info);
+                candidateSite.setOAuthId(oauthId);
+                candidateSite.setLoggedOut(false);
+            } else {
+                // New site, set site ID and info.
+                isNewSite = true;
+                candidateSite.setId(siteId);
+                candidateSite.setInfo(info);
+                candidateSite.setOAuthId(oauthId);
+
+                // Create database tables before login and before any WS call.
+                await this.migrateSiteSchemas(candidateSite);
+            }
+
+            // Try to get the site config.
+            let config: CoreSiteConfig | undefined;
+
+            try {
+                config = await this.getSiteConfig(candidateSite);
+            } catch (error) {
+                // Ignore errors if it's not a new site, we'll use the config already stored.
+                if (isNewSite) {
+                    throw error;
+                }
+            }
+
+            if (typeof config != 'undefined') {
+                candidateSite.setConfig(config);
+            }
+
+            // Add site to sites list.
+            this.addSite(siteId, siteUrl, token, info, privateToken, config, oauthId);
+            this.sites[siteId] = candidateSite;
+
+            if (login) {
+                // Turn candidate site into current site.
+                this.currentSite = candidateSite;
+                // Store session.
+                this.login(siteId);
+            }
+
+            CoreEvents.instance.trigger(CoreEventsProvider.SITE_ADDED, info, siteId);
+
+            return siteId;
+        } catch (error) {
             // Error invaliddevice is returned by Workplace server meaning the same as connecttoworkplaceapp.
             if (error && error.errorcode == 'invaliddevice') {
                 return this.treatInvalidAppVersion(this.WORKPLACE_APP, siteUrl);
             }
 
-            return Promise.reject(error);
-        });
+            throw error;
+        }
     }
 
     /**
@@ -663,8 +683,8 @@ export class CoreSitesProvider {
      * @return A promise rejected with the error info.
      */
     protected async treatInvalidAppVersion(result: number, siteUrl: string, siteId?: string): Promise<never> {
-        let errorCode;
-        let errorKey;
+        let errorCode: string | undefined;
+        let errorKey: string | undefined;
         let translateParams;
 
         switch (result) {
@@ -816,8 +836,15 @@ export class CoreSitesProvider {
      * @param oauthId OAuth ID. Only if the authentication was using an OAuth method.
      * @return Promise resolved when done.
      */
-    async addSite(id: string, siteUrl: string, token: string, info: CoreSiteInfoResponse, privateToken: string = '',
-            config?: CoreSiteConfig, oauthId?: number): Promise<void> {
+    async addSite(
+        id: string,
+        siteUrl: string,
+        token: string,
+        info: CoreSiteInfoResponse,
+        privateToken: string = '',
+        config?: CoreSiteConfig,
+        oauthId?: number,
+    ): Promise<void> {
         await this.dbReady;
 
         const entry = {
@@ -850,47 +877,55 @@ export class CoreSitesProvider {
      * @param siteId ID of the site to check. Current site id will be used otherwise.
      * @return Resolved with  if meets the requirements, rejected otherwise.
      */
-    async checkRequiredMinimumVersion(config: CoreSitePublicConfigResponse, siteId?: string): Promise<void> {
-        if (config && config.tool_mobile_minimumversion) {
-            const requiredVersion = this.convertVersionName(config.tool_mobile_minimumversion);
-            const appVersion = this.convertVersionName(CoreConfigConstants.versionname);
+    async checkRequiredMinimumVersion(config?: CoreSitePublicConfigResponse, siteId?: string): Promise<void> {
+        if (!config || !config.tool_mobile_minimumversion) {
+            return;
+        }
 
-            if (requiredVersion > appVersion) {
-                const storesConfig: CoreStoreConfig = {
-                    android: config.tool_mobile_androidappid || null,
-                    ios: config.tool_mobile_iosappid || null,
-                    desktop: config.tool_mobile_setuplink || 'https://download.moodle.org/desktop/',
-                    mobile: config.tool_mobile_setuplink || 'https://download.moodle.org/mobile/',
-                    default: config.tool_mobile_setuplink,
-                };
+        const requiredVersion = this.convertVersionName(config.tool_mobile_minimumversion);
+        const appVersion = this.convertVersionName(CoreConfigConstants.versionname);
 
-                const downloadUrl = CoreApp.instance.getAppStoreUrl(storesConfig);
+        if (requiredVersion > appVersion) {
+            const storesConfig: CoreStoreConfig = {
+                android: config.tool_mobile_androidappid,
+                ios: config.tool_mobile_iosappid,
+                desktop: config.tool_mobile_setuplink || 'https://download.moodle.org/desktop/',
+                mobile: config.tool_mobile_setuplink || 'https://download.moodle.org/mobile/',
+                default: config.tool_mobile_setuplink,
+            };
 
-                siteId = siteId || this.getCurrentSiteId();
+            siteId = siteId || this.getCurrentSiteId();
 
+            const downloadUrl = CoreApp.instance.getAppStoreUrl(storesConfig);
+
+            if (downloadUrl != null) {
                 // Do not block interface.
                 CoreDomUtils.instance.showConfirm(
                     Translate.instance.instant('core.updaterequireddesc', { $a: config.tool_mobile_minimumversion }),
                     Translate.instance.instant('core.updaterequired'),
                     Translate.instance.instant('core.download'),
-                    Translate.instance.instant(siteId ? 'core.mainmenu.logout' : 'core.cancel')).then(() => {
-                    CoreUtils.instance.openInBrowser(downloadUrl);
-                }).catch(() => {
+                    Translate.instance.instant(siteId ? 'core.mainmenu.logout' : 'core.cancel'),
+                ).then(() => CoreUtils.instance.openInBrowser(downloadUrl)).catch(() => {
                     // Do nothing.
                 });
+            } else {
+                CoreDomUtils.instance.showAlert(
+                    Translate.instance.instant('core.updaterequired'),
+                    Translate.instance.instant('core.updaterequireddesc', { $a: config.tool_mobile_minimumversion }),
+                );
+            }
 
-                if (siteId) {
-                    // Logout if it's the currentSite.
-                    if (siteId == this.getCurrentSiteId()) {
-                        await this.logout();
-                    }
-
-                    // Always expire the token.
-                    await this.setSiteLoggedOut(siteId, true);
+            if (siteId) {
+                // Logout if it's the currentSite.
+                if (siteId == this.getCurrentSiteId()) {
+                    await this.logout();
                 }
 
-                throw new CoreError('Current app version is lower than required version.');
+                // Always expire the token.
+                await this.setSiteLoggedOut(siteId, true);
             }
+
+            throw new CoreError('Current app version is lower than required version.');
         }
     }
 
@@ -952,7 +987,7 @@ export class CoreSitesProvider {
 
             return false;
         } catch (error) {
-            let config: CoreSitePublicConfigResponse;
+            let config: CoreSitePublicConfigResponse | undefined;
 
             try {
                 config = await site.getPublicConfig();
@@ -979,7 +1014,7 @@ export class CoreSitesProvider {
      *
      * @return Current site.
      */
-    getCurrentSite(): CoreSite {
+    getCurrentSite(): CoreSite | undefined {
         return this.currentSite;
     }
 
@@ -1015,11 +1050,7 @@ export class CoreSitesProvider {
      * @return Current site User ID.
      */
     getCurrentSiteUserId(): number {
-        if (this.currentSite) {
-            return this.currentSite.getUserId();
-        } else {
-            return 0;
-        }
+        return this.currentSite?.getUserId() || 0;
     }
 
     /**
@@ -1150,7 +1181,7 @@ export class CoreSitesProvider {
      * @param siteId The site ID. If not defined, current site (if available).
      * @return Promise resolved with the database.
      */
-    getSiteDb(siteId: string): Promise<SQLiteDB> {
+    getSiteDb(siteId?: string): Promise<SQLiteDB> {
         return this.getSite(siteId).then((site) => site.getDb());
     }
 
@@ -1175,7 +1206,7 @@ export class CoreSitesProvider {
 
         const sites = await this.appDB.getAllRecords<SiteDBEntry>(SITES_TABLE);
 
-        const formattedSites = [];
+        const formattedSites: CoreSiteBasicInfo[] = [];
         sites.forEach((site) => {
             if (!ids || ids.indexOf(site.id) > -1) {
                 // Parse info.
@@ -1184,7 +1215,7 @@ export class CoreSitesProvider {
                     id: site.id,
                     siteUrl: site.siteUrl,
                     fullName: siteInfo?.fullname,
-                    siteName: CoreConfigConstants.sitename ? CoreConfigConstants.sitename : siteInfo?.sitename,
+                    siteName: CoreConfigConstants.sitename ?? siteInfo?.sitename,
                     avatar: siteInfo?.userpictureurl,
                     siteHomeId: siteInfo?.siteid || 1,
                 };
@@ -1206,19 +1237,23 @@ export class CoreSitesProvider {
             // Sort sites by url and ful lname.
             sites.sort((a, b) => {
                 // First compare by site url without the protocol.
-                let compareA = a.siteUrl.replace(/^https?:\/\//, '').toLowerCase();
-                let compareB = b.siteUrl.replace(/^https?:\/\//, '').toLowerCase();
-                const compare = compareA.localeCompare(compareB);
+                const urlA = a.siteUrl.replace(/^https?:\/\//, '').toLowerCase();
+                const urlB = b.siteUrl.replace(/^https?:\/\//, '').toLowerCase();
+                const compare = urlA.localeCompare(urlB);
 
                 if (compare !== 0) {
                     return compare;
                 }
 
                 // If site url is the same, use fullname instead.
-                compareA = a.fullName.toLowerCase().trim();
-                compareB = b.fullName.toLowerCase().trim();
+                const fullNameA = a.fullName?.toLowerCase().trim();
+                const fullNameB = b.fullName?.toLowerCase().trim();
 
-                return compareA.localeCompare(compareB);
+                if (!fullNameA || !fullNameB) {
+                    return 0;
+                }
+
+                return fullNameA.localeCompare(fullNameB);
             });
 
             return sites;
@@ -1279,10 +1314,10 @@ export class CoreSitesProvider {
         await this.dbReady;
 
         let siteId;
-        const promises = [];
+        const promises: Promise<unknown>[] = [];
 
         if (this.currentSite) {
-            const siteConfig = <CoreSiteConfig> this.currentSite.getStoredConfig();
+            const siteConfig = this.currentSite.getStoredConfig();
             siteId = this.currentSite.getId();
 
             this.currentSite = undefined;
@@ -1418,7 +1453,7 @@ export class CoreSitesProvider {
             }
 
             // Try to get the site config.
-            let config;
+            let config: CoreSiteConfig | undefined;
 
             try {
                 config = await this.getSiteConfig(site);
@@ -1426,10 +1461,9 @@ export class CoreSitesProvider {
                 // Error getting config, keep the current one.
             }
 
-            const newValues = {
+            const newValues: Record<string, string | number> = {
                 info: JSON.stringify(info),
                 loggedOut: site.isLoggedOut() ? 1 : 0,
-                config: undefined,
             };
 
             if (typeof config != 'undefined') {
@@ -1475,7 +1509,7 @@ export class CoreSitesProvider {
 
         // If prioritize is true, check current site first.
         if (prioritize && this.currentSite && this.currentSite.containsUrl(url)) {
-            if (!username || this.currentSite.getInfo().username == username) {
+            if (!username || this.currentSite?.getInfo()?.username == username) {
                 return [this.currentSite.getId()];
             }
         }
@@ -1498,8 +1532,8 @@ export class CoreSitesProvider {
 
         try {
             const siteEntries = await this.appDB.getAllRecords<SiteDBEntry>(SITES_TABLE);
-            const ids = [];
-            const promises = [];
+            const ids: string[] = [];
+            const promises: Promise<unknown>[] = [];
 
             siteEntries.forEach((site) => {
                 if (!this.sites[site.id]) {
@@ -1507,7 +1541,7 @@ export class CoreSitesProvider {
                 }
 
                 if (this.sites[site.id].containsUrl(url)) {
-                    if (!username || this.sites[site.id].getInfo().username == username) {
+                    if (!username || this.sites[site.id].getInfo()?.username == username) {
                         ids.push(site.id);
                     }
                 }
@@ -1553,15 +1587,13 @@ export class CoreSitesProvider {
      * @param site The site to get the config.
      * @return Promise resolved with config if available.
      */
-    protected async getSiteConfig(site: CoreSite): Promise<CoreSiteConfig> {
+    protected async getSiteConfig(site: CoreSite): Promise<CoreSiteConfig | undefined> {
         if (!site.wsAvailable('tool_mobile_get_config')) {
             // WS not available, cannot get config.
             return;
         }
 
-        const config = <CoreSiteConfig> await site.getConfig(undefined, true);
-
-        return config;
+        return await site.getConfig(undefined, true);
     }
 
     /**
@@ -1611,7 +1643,7 @@ export class CoreSitesProvider {
     wsAvailableInCurrentSite(method: string, checkPrefix: boolean = true): boolean {
         const site = this.getCurrentSite();
 
-        return site && site.wsAvailable(method, checkPrefix);
+        return site ? site.wsAvailable(method, checkPrefix) : false;
     }
 
     /**
@@ -1659,6 +1691,10 @@ export class CoreSitesProvider {
      * @return Promise resolved when done.
      */
     migrateSiteSchemas(site: CoreSite): Promise<void> {
+        if (!site.id) {
+            return Promise.resolve();
+        }
+
         if (this.siteSchemasMigration[site.id]) {
             return this.siteSchemasMigration[site.id];
         }
@@ -1672,7 +1708,7 @@ export class CoreSitesProvider {
         this.siteSchemasMigration[site.id] = promise;
 
         return promise.finally(() => {
-            delete this.siteSchemasMigration[site.id];
+            delete this.siteSchemasMigration[site.id!];
         });
     }
 
@@ -1694,7 +1730,7 @@ export class CoreSitesProvider {
             versions[record.name] = record.version;
         });
 
-        const promises = [];
+        const promises: Promise<void>[] = [];
         for (const name in schemas) {
             const schema = schemas[name];
             const oldVersion = versions[name] || 0;
@@ -1720,6 +1756,10 @@ export class CoreSitesProvider {
      * @return Promise resolved when done.
      */
     protected async applySiteSchema(site: CoreSite, schema: CoreRegisteredSiteSchema, oldVersion: number): Promise<void> {
+        if (!site.id) {
+            return;
+        }
+
         const db = site.getDb();
 
         if (schema.tables) {
@@ -1741,31 +1781,31 @@ export class CoreSitesProvider {
      * @return Promise resolved with site to use and the list of sites that have
      *         the URL. Site will be undefined if it isn't the root URL of any stored site.
      */
-    isStoredRootURL(url: string, username?: string): Promise<{site: CoreSite; siteIds: string[]}> {
+    async isStoredRootURL(url: string, username?: string): Promise<{site?: CoreSite; siteIds: string[]}> {
         // Check if the site is stored.
-        return this.getSiteIdsFromUrl(url, true, username).then((siteIds) => {
-            const result = {
-                siteIds,
-                site: undefined,
-            };
+        const siteIds = await this.getSiteIdsFromUrl(url, true, username);
 
-            if (siteIds.length > 0) {
-                // If more than one site is returned it usually means there are different users stored. Use any of them.
-                return this.getSite(siteIds[0]).then((site) => {
-                    const siteUrl = CoreTextUtils.instance.removeEndingSlash(
-                        CoreUrlUtils.instance.removeProtocolAndWWW(site.getURL()));
-                    const treatedUrl = CoreTextUtils.instance.removeEndingSlash(CoreUrlUtils.instance.removeProtocolAndWWW(url));
-
-                    if (siteUrl == treatedUrl) {
-                        result.site = site;
-                    }
-
-                    return result;
-                });
-            }
+        const result: {site?: CoreSite; siteIds: string[]} = {
+            siteIds,
+        };
 
+        if (!siteIds.length) {
             return result;
-        });
+        }
+
+        // If more than one site is returned it usually means there are different users stored. Use any of them.
+        const site = await this.getSite(siteIds[0]);
+
+        const siteUrl = CoreTextUtils.instance.removeEndingSlash(
+            CoreUrlUtils.instance.removeProtocolAndWWW(site.getURL()),
+        );
+        const treatedUrl = CoreTextUtils.instance.removeEndingSlash(CoreUrlUtils.instance.removeProtocolAndWWW(url));
+
+        if (siteUrl == treatedUrl) {
+            result.site = site;
+        }
+
+        return result;
     }
 
     /**
@@ -1775,12 +1815,12 @@ export class CoreSitesProvider {
      * @return Name of the site schemas.
      */
     getSiteTableSchemasToClear(site: CoreSite): string[] {
-        let reset = [];
+        let reset: string[] = [];
         for (const name in this.siteSchemas) {
             const schema = this.siteSchemas[name];
 
             if (schema.canBeCleared && (!schema.siteId || site.getId() == schema.siteId)) {
-                reset = reset.concat(this.siteSchemas[name].canBeCleared);
+                reset = reset.concat(schema.canBeCleared);
             }
         }
 
@@ -1900,17 +1940,17 @@ export type CoreSiteBasicInfo = {
     /**
      * User's full name.
      */
-    fullName: string;
+    fullName?: string;
 
     /**
      * Site's name.
      */
-    siteName: string;
+    siteName?: string;
 
     /**
      * User's avatar.
      */
-    avatar: string;
+    avatar?: string;
 
     /**
      * Badge to display in the site.
diff --git a/src/app/services/utils/dom.ts b/src/app/services/utils/dom.ts
index 97b4e3472..b2e617bb6 100644
--- a/src/app/services/utils/dom.ts
+++ b/src/app/services/utils/dom.ts
@@ -30,6 +30,7 @@ import { CoreConstants } from '@core/constants';
 import { CoreIonLoadingElement } from '@classes/ion-loading';
 import { CoreCanceledError } from '@classes/errors/cancelederror';
 import { CoreError } from '@classes/errors/error';
+import { CoreSilentError } from '@classes/errors/silenterror';
 
 import { makeSingleton, Translate, AlertController, LoadingController, ToastController } from '@singletons/core.singletons';
 import { CoreLogger } from '@singletons/logger';
@@ -40,14 +41,15 @@ import { CoreLogger } from '@singletons/logger';
 @Injectable()
 export class CoreDomUtilsProvider {
 
+    protected readonly INSTANCE_ID_ATTR_NAME = 'core-instance-id';
+
     // List of input types that support keyboard.
     protected readonly INPUT_SUPPORT_KEYBOARD: string[] = ['date', 'datetime', 'datetime-local', 'email', 'month', 'number',
         'password', 'search', 'tel', 'text', 'time', 'url', 'week'];
-    protected readonly INSTANCE_ID_ATTR_NAME: string = 'core-instance-id';
 
     protected template: HTMLTemplateElement = document.createElement('template'); // A template element to convert HTML to element.
 
-    protected matchesFn: string; // Name of the "matches" function to use when simulating a closest call.
+    protected matchesFunctionName?: string; // Name of the "matches" function to use when simulating a closest call.
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected instances: {[id: string]: any} = {}; // Store component/directive instances by id.
     protected lastInstanceId = 0;
@@ -58,10 +60,17 @@ export class CoreDomUtilsProvider {
     constructor(protected domSanitizer: DomSanitizer) {
         this.logger = CoreLogger.getInstance('CoreDomUtilsProvider');
 
+        this.init();
+    }
+
+    /**
+     * Init some properties.
+     */
+    protected async init(): Promise<void> {
         // Check if debug messages should be displayed.
-        CoreConfig.instance.get(CoreConstants.SETTINGS_DEBUG_DISPLAY, false).then((debugDisplay) => {
-            this.debugDisplay = !!debugDisplay;
-        });
+        const debugDisplay = await CoreConfig.instance.get<number>(CoreConstants.SETTINGS_DEBUG_DISPLAY, 0);
+
+        this.debugDisplay = debugDisplay != 0;
     }
 
     /**
@@ -73,17 +82,21 @@ export class CoreDomUtilsProvider {
      * @param selector Selector to search.
      * @return Closest ancestor.
      */
-    closest(element: Element, selector: string): Element {
+    closest(element: Element | undefined | null, selector: string): Element | null {
+        if (!element) {
+            return null;
+        }
+    
         // Try to use closest if the browser supports it.
         if (typeof element.closest == 'function') {
             return element.closest(selector);
         }
 
-        if (!this.matchesFn) {
+        if (!this.matchesFunctionName) {
             // Find the matches function supported by the browser.
             ['matches', 'webkitMatchesSelector', 'mozMatchesSelector', 'msMatchesSelector', 'oMatchesSelector'].some((fn) => {
                 if (typeof document.body[fn] == 'function') {
-                    this.matchesFn = fn;
+                    this.matchesFunctionName = fn;
 
                     return true;
                 }
@@ -91,18 +104,22 @@ export class CoreDomUtilsProvider {
                 return false;
             });
 
-            if (!this.matchesFn) {
-                return;
+            if (!this.matchesFunctionName) {
+                return null;
             }
         }
 
         // Traverse parents.
-        while (element) {
-            if (element[this.matchesFn](selector)) {
-                return element;
+        let elementToTreat: Element | null = element;
+
+        while (elementToTreat) {
+            if (elementToTreat[this.matchesFunctionName](selector)) {
+                return elementToTreat;
             }
-            element = element.parentElement;
+            elementToTreat = elementToTreat.parentElement;
         }
+
+        return null;
     }
 
     /**
@@ -116,7 +133,7 @@ export class CoreDomUtilsProvider {
      * @param alwaysConfirm True to show a confirm even if the size isn't high, false otherwise.
      * @return Promise resolved when the user confirms or if no confirm needed.
      */
-    confirmDownloadSize(
+    async confirmDownloadSize(
         size: {size: number; total: boolean},
         message?: string,
         unknownMessage?: string,
@@ -126,73 +143,88 @@ export class CoreDomUtilsProvider {
     ): Promise<void> {
         const readableSize = CoreTextUtils.instance.bytesToSize(size.size, 2);
 
-        const getAvailableBytes = new Promise((resolve): void => {
+        const getAvailableBytes = async (): Promise<number | null> => {
             if (CoreApp.instance.isDesktop()) {
                 // Free space calculation is not supported on desktop.
-                resolve(null);
-            } else {
-                CoreFile.instance.calculateFreeSpace().then((availableBytes) => {
-                    if (CoreApp.instance.isAndroid()) {
-                        return availableBytes;
-                    } else {
-                        // Space calculation is not accurate on iOS, but it gets more accurate when space is lower.
-                        // We'll only use it when space is <500MB, or we're downloading more than twice the reported space.
-                        if (availableBytes < CoreConstants.IOS_FREE_SPACE_THRESHOLD || size.size > availableBytes / 2) {
-                            return availableBytes;
-                        } else {
-                            return null;
-                        }
-                    }
-                }).then((availableBytes) => {
-                    resolve(availableBytes);
-                });
+                return null;
             }
-        });
 
-        const getAvailableSpace = getAvailableBytes.then((availableBytes: number) => {
+            const availableBytes = await CoreFile.instance.calculateFreeSpace();
+
+            if (CoreApp.instance.isAndroid()) {
+                return availableBytes;
+            } else {
+                // Space calculation is not accurate on iOS, but it gets more accurate when space is lower.
+                // We'll only use it when space is <500MB, or we're downloading more than twice the reported space.
+                if (availableBytes < CoreConstants.IOS_FREE_SPACE_THRESHOLD || size.size > availableBytes / 2) {
+                    return availableBytes;
+                } else {
+                    return null;
+                }
+            }
+        };
+
+        const getAvailableSpace = (availableBytes: number | null): string => {
             if (availableBytes === null) {
                 return '';
             } else {
                 const availableSize = CoreTextUtils.instance.bytesToSize(availableBytes, 2);
+
                 if (CoreApp.instance.isAndroid() && size.size > availableBytes - CoreConstants.MINIMUM_FREE_SPACE) {
-                    return Promise.reject(new CoreError(Translate.instance.instant('core.course.insufficientavailablespace',
-                        { size: readableSize })));
+                    throw new CoreError(
+                        Translate.instance.instant(
+                            'core.course.insufficientavailablespace',
+                            { size: readableSize },
+                        ),
+                    );
                 }
 
                 return Translate.instance.instant('core.course.availablespace', { available: availableSize });
             }
-        });
+        };
 
-        return getAvailableSpace.then((availableSpace) => {
-            wifiThreshold = typeof wifiThreshold == 'undefined' ? CoreConstants.WIFI_DOWNLOAD_THRESHOLD : wifiThreshold;
-            limitedThreshold = typeof limitedThreshold == 'undefined' ? CoreConstants.DOWNLOAD_THRESHOLD : limitedThreshold;
+        const availableBytes = await getAvailableBytes();
 
-            let wifiPrefix = '';
-            if (CoreApp.instance.isNetworkAccessLimited()) {
-                wifiPrefix = Translate.instance.instant('core.course.confirmlimiteddownload');
-            }
+        const availableSpace = getAvailableSpace(availableBytes);
 
-            if (size.size < 0 || (size.size == 0 && !size.total)) {
-                // Seems size was unable to be calculated. Show a warning.
-                unknownMessage = unknownMessage || 'core.course.confirmdownloadunknownsize';
+        wifiThreshold = typeof wifiThreshold == 'undefined' ? CoreConstants.WIFI_DOWNLOAD_THRESHOLD : wifiThreshold;
+        limitedThreshold = typeof limitedThreshold == 'undefined' ? CoreConstants.DOWNLOAD_THRESHOLD : limitedThreshold;
 
-                return this.showConfirm(wifiPrefix + Translate.instance.instant(
-                    unknownMessage, { availableSpace: availableSpace }));
-            } else if (!size.total) {
-                // Filesize is only partial.
+        let wifiPrefix = '';
+        if (CoreApp.instance.isNetworkAccessLimited()) {
+            wifiPrefix = Translate.instance.instant('core.course.confirmlimiteddownload');
+        }
 
-                return this.showConfirm(wifiPrefix + Translate.instance.instant('core.course.confirmpartialdownloadsize',
-                    { size: readableSize, availableSpace: availableSpace }));
-            } else if (alwaysConfirm || size.size >= wifiThreshold ||
+        if (size.size < 0 || (size.size == 0 && !size.total)) {
+            // Seems size was unable to be calculated. Show a warning.
+            unknownMessage = unknownMessage || 'core.course.confirmdownloadunknownsize';
+
+            return this.showConfirm(
+                wifiPrefix + Translate.instance.instant(
+                    unknownMessage,
+                    { availableSpace: availableSpace },
+                ),
+            );
+        } else if (!size.total) {
+            // Filesize is only partial.
+
+            return this.showConfirm(
+                wifiPrefix + Translate.instance.instant(
+                    'core.course.confirmpartialdownloadsize',
+                    { size: readableSize, availableSpace: availableSpace },
+                ),
+            );
+        } else if (alwaysConfirm || size.size >= wifiThreshold ||
                 (CoreApp.instance.isNetworkAccessLimited() && size.size >= limitedThreshold)) {
-                message = message || (size.size === 0 ? 'core.course.confirmdownloadzerosize' : 'core.course.confirmdownload');
+            message = message || (size.size === 0 ? 'core.course.confirmdownloadzerosize' : 'core.course.confirmdownload');
 
-                return this.showConfirm(wifiPrefix + Translate.instance.instant(message,
-                    { size: readableSize, availableSpace: availableSpace }));
-            }
-
-            return Promise.resolve();
-        });
+            return this.showConfirm(
+                wifiPrefix + Translate.instance.instant(
+                    message,
+                    { size: readableSize, availableSpace: availableSpace },
+                ),
+            );
+        }
     }
 
     /**
@@ -255,11 +287,10 @@ export class CoreDomUtilsProvider {
         this.logger.error('The function extractDownloadableFilesFromHtml has been moved to CoreFilepoolProvider.' +
                 ' Please use that function instead of this one.');
 
-        const urls = [];
+        const urls: string[] = [];
 
         const element = this.convertToElement(html);
-        const elements: (HTMLAnchorElement | HTMLImageElement | HTMLAudioElement | HTMLVideoElement | HTMLSourceElement |
-            HTMLTrackElement)[] = Array.from(element.querySelectorAll('a, img, audio, video, source, track'));
+        const elements: AnchorOrMediaElement[] = Array.from(element.querySelectorAll('a, img, audio, video, source, track'));
 
         for (let i = 0; i < elements.length; i++) {
             const element = elements[i];
@@ -271,7 +302,7 @@ export class CoreDomUtilsProvider {
 
             // Treat video poster.
             if (element.tagName == 'VIDEO' && element.getAttribute('poster')) {
-                url = element.getAttribute('poster');
+                url = element.getAttribute('poster') || '';
                 if (url && CoreUrlUtils.instance.isDownloadableUrl(url) && urls.indexOf(url) == -1) {
                     urls.push(url);
                 }
@@ -305,7 +336,7 @@ export class CoreDomUtilsProvider {
      */
     extractUrlsFromCSS(code: string): string[] {
         // First of all, search all the url(...) occurrences that don't include "data:".
-        const urls = [];
+        const urls: string[] = [];
         const matches = code.match(/url\(\s*["']?(?!data:)([^)]+)\)/igm);
 
         if (!matches) {
@@ -394,7 +425,7 @@ export class CoreDomUtilsProvider {
      * @param selector Selector to search.
      * @return Selection contents. Undefined if not found.
      */
-    getContentsOfElement(element: HTMLElement, selector: string): string {
+    getContentsOfElement(element: HTMLElement, selector: string): string | undefined {
         if (element) {
             const selected = element.querySelector(selector);
             if (selected) {
@@ -447,7 +478,7 @@ export class CoreDomUtilsProvider {
      * @param attribute Attribute to get.
      * @return Attribute value.
      */
-    getHTMLElementAttribute(html: string, attribute: string): string {
+    getHTMLElementAttribute(html: string, attribute: string): string | null {
         return this.convertToElement(html).children[0].getAttribute(attribute);
     }
 
@@ -584,8 +615,8 @@ export class CoreDomUtilsProvider {
      * @param positionParentClass Parent Class where to stop calculating the position. Default inner-scroll.
      * @return positionLeft, positionTop of the element relative to.
      */
-    getElementXY(container: HTMLElement, selector?: string, positionParentClass?: string): number[] {
-        let element: HTMLElement = <HTMLElement> (selector ? container.querySelector(selector) : container);
+    getElementXY(container: HTMLElement, selector?: string, positionParentClass?: string): number[] | null {
+        let element: HTMLElement | null = <HTMLElement> (selector ? container.querySelector(selector) : container);
         let positionTop = 0;
         let positionLeft = 0;
 
@@ -645,9 +676,9 @@ export class CoreDomUtilsProvider {
      * @param needsTranslate Whether the error needs to be translated.
      * @return Error message, null if no error should be displayed.
      */
-    getErrorMessage(error: CoreError | CoreTextErrorObject | string, needsTranslate?: boolean): string {
+    getErrorMessage(error: CoreError | CoreTextErrorObject | string, needsTranslate?: boolean): string | null {
         let extraInfo = '';
-        let errorMessage: string;
+        let errorMessage: string | undefined;
 
         if (typeof error == 'object') {
             if (this.debugDisplay) {
@@ -657,19 +688,21 @@ export class CoreDomUtilsProvider {
                 }
                 if ('backtrace' in error && error.backtrace) {
                     extraInfo += '<br><br>' + CoreTextUtils.instance.replaceNewLines(
-                        CoreTextUtils.instance.escapeHTML(error.backtrace, false), '<br>');
+                        CoreTextUtils.instance.escapeHTML(error.backtrace, false),
+                        '<br>',
+                    );
                 }
 
                 // eslint-disable-next-line no-console
                 console.error(error);
             }
 
-            // We received an object instead of a string. Search for common properties.
-            if (this.isCanceledError(error)) {
-                // It's a canceled error, don't display an error.
+            if (this.isSilentError(error)) {
+                // It's a silent error, don't display an error.
                 return null;
             }
 
+            // We received an object instead of a string. Search for common properties.
             errorMessage = CoreTextUtils.instance.getErrorMessageFromError(error);
             if (!errorMessage) {
                 // No common properties found, just stringify it.
@@ -712,7 +745,7 @@ export class CoreDomUtilsProvider {
     getInstanceByElement(element: Element): any {
         const id = element.getAttribute(this.INSTANCE_ID_ATTR_NAME);
 
-        return this.instances[id];
+        return id && this.instances[id];
     }
 
     /**
@@ -725,6 +758,16 @@ export class CoreDomUtilsProvider {
         return error instanceof CoreCanceledError;
     }
 
+    /**
+     * Check whether an error is an error caused because the user canceled a showConfirm.
+     *
+     * @param error Error to check.
+     * @return Whether it's a canceled error.
+     */
+    isSilentError(error: CoreError | CoreTextErrorObject | string): boolean {
+        return error instanceof CoreSilentError;
+    }
+
     /**
      * Wait an element to exists using the findFunction.
      *
@@ -898,7 +941,7 @@ export class CoreDomUtilsProvider {
      */
     removeInstanceByElement(element: Element): void {
         const id = element.getAttribute(this.INSTANCE_ID_ATTR_NAME);
-        delete this.instances[id];
+        id && delete this.instances[id];
     }
 
     /**
@@ -946,7 +989,8 @@ export class CoreDomUtilsProvider {
         // Treat elements with src (img, audio, video, ...).
         const media = Array.from(element.querySelectorAll('img, video, audio, source, track'));
         media.forEach((media: HTMLElement) => {
-            let newSrc = paths[CoreTextUtils.instance.decodeURIComponent(media.getAttribute('src'))];
+            const currentSrc = media.getAttribute('src');
+            const newSrc = currentSrc ? paths[CoreTextUtils.instance.decodeURIComponent(currentSrc)] : undefined;
 
             if (typeof newSrc != 'undefined') {
                 media.setAttribute('src', newSrc);
@@ -954,9 +998,10 @@ export class CoreDomUtilsProvider {
 
             // Treat video posters.
             if (media.tagName == 'VIDEO' && media.getAttribute('poster')) {
-                newSrc = paths[CoreTextUtils.instance.decodeURIComponent(media.getAttribute('poster'))];
-                if (typeof newSrc !== 'undefined') {
-                    media.setAttribute('poster', newSrc);
+                const currentPoster = media.getAttribute('poster');
+                const newPoster = paths[CoreTextUtils.instance.decodeURIComponent(currentPoster!)];
+                if (typeof newPoster !== 'undefined') {
+                    media.setAttribute('poster', newPoster);
                 }
             }
         });
@@ -964,14 +1009,14 @@ export class CoreDomUtilsProvider {
         // Now treat links.
         const anchors = Array.from(element.querySelectorAll('a'));
         anchors.forEach((anchor: HTMLElement) => {
-            const href = CoreTextUtils.instance.decodeURIComponent(anchor.getAttribute('href'));
-            const newUrl = paths[href];
+            const currentHref = anchor.getAttribute('href');
+            const newHref = currentHref ? paths[CoreTextUtils.instance.decodeURIComponent(currentHref)] : undefined;
 
-            if (typeof newUrl != 'undefined') {
-                anchor.setAttribute('href', newUrl);
+            if (typeof newHref != 'undefined') {
+                anchor.setAttribute('href', newHref);
 
                 if (typeof anchorFn == 'function') {
-                    anchorFn(anchor, href);
+                    anchorFn(anchor, newHref);
                 }
             }
         });
@@ -990,7 +1035,7 @@ export class CoreDomUtilsProvider {
      * @deprecated since 3.9.5. Use directly the IonContent class.
      */
     scrollTo(content: IonContent, x: number, y: number, duration?: number): Promise<void> {
-        return content?.scrollByPoint(x, y, duration);
+        return content?.scrollByPoint(x, y, duration || 0);
     }
 
     /**
@@ -1080,7 +1125,7 @@ export class CoreDomUtilsProvider {
             return false;
         }
 
-        content?.scrollByPoint(position[0], position[1], duration);
+        content?.scrollByPoint(position[0], position[1], duration || 0);
 
         return true;
     }
@@ -1108,7 +1153,7 @@ export class CoreDomUtilsProvider {
                 return false;
             }
 
-            content?.scrollByPoint(position[0], position[1], duration);
+            content?.scrollByPoint(position[0], position[1], duration || 0);
 
             return true;
         } catch (error) {
@@ -1186,31 +1231,36 @@ export class CoreDomUtilsProvider {
 
         const alert = await AlertController.instance.create(options);
 
+        // eslint-disable-next-line promise/catch-or-return
         alert.present().then(() => {
             if (hasHTMLTags) {
                 // Treat all anchors so they don't override the app.
-                const alertMessageEl: HTMLElement = alert.querySelector('.alert-message');
-                this.treatAnchors(alertMessageEl);
+                const alertMessageEl: HTMLElement | null = alert.querySelector('.alert-message');
+                alertMessageEl && this.treatAnchors(alertMessageEl);
             }
+
+            return;
         });
 
         // Store the alert and remove it when dismissed.
         this.displayedAlerts[alertId] = alert;
 
         // // Set the callbacks to trigger an observable event.
+        // eslint-disable-next-line promise/catch-or-return, promise/always-return
         alert.onDidDismiss().then(() => {
             delete this.displayedAlerts[alertId];
         });
 
-        if (autocloseTime > 0) {
+        if (autocloseTime && autocloseTime > 0) {
             setTimeout(async () => {
                 await alert.dismiss();
 
                 if (options.buttons) {
                     // Execute dismiss function if any.
-                    const cancelButton = <AlertButton> options.buttons.find((button) => typeof button != 'string' &&
-                        typeof button.handler != 'undefined' && button.role == 'cancel');
-                    cancelButton?.handler(null);
+                    const cancelButton = <AlertButton> options.buttons.find(
+                        (button) => typeof button != 'string' && typeof button.handler != 'undefined' && button.role == 'cancel',
+                    );
+                    cancelButton.handler?.(null);
                 }
             }, autocloseTime);
         }
@@ -1248,8 +1298,13 @@ export class CoreDomUtilsProvider {
         translateArgs: Record<string, string> = {},
         options?: AlertOptions,
     ): Promise<void> {
-        return this.showConfirm(Translate.instance.instant(translateMessage, translateArgs), undefined,
-            Translate.instance.instant('core.delete'), undefined, options);
+        return this.showConfirm(
+            Translate.instance.instant(translateMessage, translateArgs),
+            undefined,
+            Translate.instance.instant('core.delete'),
+            undefined,
+            options,
+        );
     }
 
     /**
@@ -1306,7 +1361,7 @@ export class CoreDomUtilsProvider {
     ): Promise<HTMLIonAlertElement | null> {
         if (this.isCanceledError(error)) {
             // It's a canceled error, don't display an error.
-            return null;
+            return Promise.resolve(null);
         }
 
         const message = this.getErrorMessage(error, needsTranslate);
@@ -1339,7 +1394,7 @@ export class CoreDomUtilsProvider {
             return null;
         }
 
-        let errorMessage = error;
+        let errorMessage = error || undefined;
 
         if (error && typeof error != 'string') {
             errorMessage = CoreTextUtils.instance.getErrorMessageFromError(error);
@@ -1428,8 +1483,8 @@ export class CoreDomUtilsProvider {
         const isDevice = CoreApp.instance.isAndroid() || CoreApp.instance.isIOS();
         if (!isDevice) {
             // Treat all anchors so they don't override the app.
-            const alertMessageEl: HTMLElement = alert.querySelector('.alert-message');
-            this.treatAnchors(alertMessageEl);
+            const alertMessageEl: HTMLElement | null = alert.querySelector('.alert-message');
+            alertMessageEl && this.treatAnchors(alertMessageEl);
         }
     }
 
@@ -1448,8 +1503,7 @@ export class CoreDomUtilsProvider {
         header?: string,
         placeholder?: string,
         type: TextFieldTypes | 'checkbox' | 'radio' | 'textarea' = 'password',
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    ): Promise<any> {
+    ): Promise<any> { // eslint-disable-line @typescript-eslint/no-explicit-any
         return new Promise((resolve, reject) => {
             placeholder = placeholder ?? Translate.instance.instant('core.login.password');
 
@@ -1537,7 +1591,7 @@ export class CoreDomUtilsProvider {
      * @param instance The instance to store.
      * @return ID to identify the instance.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     storeInstanceByElement(element: Element, instance: any): string {
         const id = String(this.lastInstanceId++);
 
@@ -1607,7 +1661,7 @@ export class CoreDomUtilsProvider {
      * @param componentId An ID to use in conjunction with the component.
      * @param fullScreen Whether the modal should be full screen.
      */
-    viewImage(image: string, title?: string, component?: string, componentId?: string | number, fullScreen?: boolean): void {
+    viewImage(image: string, title?: string | null, component?: string, componentId?: string | number, fullScreen?: boolean): void {
         // @todo
     }
 
@@ -1619,7 +1673,7 @@ export class CoreDomUtilsProvider {
      */
     waitForImages(element: HTMLElement): Promise<boolean> {
         const imgs = Array.from(element.querySelectorAll('img'));
-        const promises = [];
+        const promises: Promise<void>[] = [];
         let hasImgToLoad = false;
 
         imgs.forEach((img) => {
@@ -1651,7 +1705,7 @@ export class CoreDomUtilsProvider {
      */
     wrapElement(el: HTMLElement, wrapper: HTMLElement): void {
         // Insert the wrapper before the element.
-        el.parentNode.insertBefore(wrapper, el);
+        el.parentNode?.insertBefore(wrapper, el);
         // Now move the element into the wrapper.
         wrapper.appendChild(el);
     }
@@ -1680,7 +1734,7 @@ export class CoreDomUtilsProvider {
      * @param online Whether the action was done in offline or not.
      * @param siteId The site affected. If not provided, no site affected.
      */
-    triggerFormSubmittedEvent(formRef: ElementRef, online?: boolean, siteId?: string): void {
+    triggerFormSubmittedEvent(formRef: ElementRef | undefined, online?: boolean, siteId?: string): void {
         if (!formRef) {
             return;
         }
@@ -1695,3 +1749,6 @@ export class CoreDomUtilsProvider {
 }
 
 export class CoreDomUtils extends makeSingleton(CoreDomUtilsProvider) {}
+
+type AnchorOrMediaElement =
+    HTMLAnchorElement | HTMLImageElement | HTMLAudioElement | HTMLVideoElement | HTMLSourceElement | HTMLTrackElement;
diff --git a/src/app/services/utils/iframe.ts b/src/app/services/utils/iframe.ts
index ed8f61b72..eae0e490b 100644
--- a/src/app/services/utils/iframe.ts
+++ b/src/app/services/utils/iframe.ts
@@ -423,7 +423,7 @@ export class CoreIframeUtilsProvider {
             if (!CoreSites.instance.isLoggedIn()) {
                 CoreUtils.instance.openInBrowser(link.href);
             } else {
-                await CoreSites.instance.getCurrentSite().openInBrowserWithAutoLoginIfSameSite(link.href);
+                await CoreSites.instance.getCurrentSite()!.openInBrowserWithAutoLoginIfSameSite(link.href);
             }
         } else if (link.target == '_parent' || link.target == '_top' || link.target == '_blank') {
             // Opening links with _parent, _top or _blank can break the app. We'll open it in InAppBrowser.
diff --git a/src/app/services/utils/mimetype.ts b/src/app/services/utils/mimetype.ts
index d6b0e0767..63414cbd8 100644
--- a/src/app/services/utils/mimetype.ts
+++ b/src/app/services/utils/mimetype.ts
@@ -401,7 +401,7 @@ export class CoreMimetypeUtilsProvider {
      * @param capitalise If true, capitalises first character of result.
      * @return Type description.
      */
-    getMimetypeDescription(obj: FileEntry | { filename: string; mimetype: string } | string, capitalise?: boolean): string {
+    getMimetypeDescription(obj: FileEntry | CoreWSExternalFile | string, capitalise?: boolean): string {
         const langPrefix = 'assets.mimetypes.';
         let filename: string | undefined = '';
         let mimetype: string | undefined = '';
diff --git a/src/app/services/utils/text.ts b/src/app/services/utils/text.ts
index dd202be38..2a3984044 100644
--- a/src/app/services/utils/text.ts
+++ b/src/app/services/utils/text.ts
@@ -417,7 +417,7 @@ export class CoreTextUtilsProvider {
      * @param doubleEncode If false, it will not convert existing html entities. Defaults to true.
      * @return Escaped text.
      */
-    escapeHTML(text: string | number, doubleEncode: boolean = true): string {
+    escapeHTML(text?: string | number | null, doubleEncode: boolean = true): string {
         if (typeof text == 'undefined' || text === null || (typeof text == 'number' && isNaN(text))) {
             return '';
         } else if (typeof text != 'string') {
@@ -670,7 +670,7 @@ export class CoreTextUtilsProvider {
      * @param text Text to treat.
      * @return Treated text.
      */
-    removeEndingSlash(text: string): string {
+    removeEndingSlash(text?: string): string {
         if (!text) {
             return '';
         }
diff --git a/src/app/services/ws.ts b/src/app/services/ws.ts
index a97eccea7..b1952f63b 100644
--- a/src/app/services/ws.ts
+++ b/src/app/services/ws.ts
@@ -44,7 +44,7 @@ import { CoreAjaxWSError } from '@classes/errors/ajaxwserror';
 export class CoreWSProvider {
 
     protected logger: CoreLogger;
-    protected mimeTypeCache: {[url: string]: string} = {}; // A "cache" to store file mimetypes to decrease HEAD requests.
+    protected mimeTypeCache: {[url: string]: string | null} = {}; // A "cache" to store file mimetypes to decrease HEAD requests.
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
     protected ongoingCalls: {[queueItemId: string]: Promise<any>} = {};
     protected retryCalls: RetryCall[] = [];
@@ -53,11 +53,18 @@ export class CoreWSProvider {
     constructor() {
         this.logger = CoreLogger.getInstance('CoreWSProvider');
 
-        Platform.instance.ready().then(() => {
-            if (CoreApp.instance.isIOS()) {
-                NativeHttp.instance.setHeader('*', 'User-Agent', navigator.userAgent);
-            }
-        });
+        this.init();
+    }
+
+    /**
+     * Initialize some data.
+     */
+    protected async init(): Promise<void> {
+        await Platform.instance.ready();
+
+        if (CoreApp.instance.isIOS()) {
+            NativeHttp.instance.setHeader('*', 'User-Agent', navigator.userAgent);
+        }
     }
 
     /**
@@ -67,8 +74,7 @@ export class CoreWSProvider {
      * @param siteUrl Complete site url to perform the call.
      * @param ajaxData Arguments to pass to the method.
      * @param preSets Extra settings and information.
-     * @return Deferred promise resolved with the response data in success and rejected with the error message
-     *         if it fails.
+     * @return Deferred promise resolved with the response data in success and rejected with the error if it fails.
      */
     protected addToRetryQueue<T = unknown>(method: string, siteUrl: string, data: unknown, preSets: CoreWSPreSets): Promise<T> {
         const call = {
@@ -94,9 +100,9 @@ export class CoreWSProvider {
      */
     call<T = unknown>(method: string, data: unknown, preSets: CoreWSPreSets): Promise<T> {
         if (!preSets) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.unexpectederror')));
+            throw new CoreError(Translate.instance.instant('core.unexpectederror'));
         } else if (!CoreApp.instance.isOnline()) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.networkerrormsg')));
+            throw new CoreError(Translate.instance.instant('core.networkerrormsg'));
         }
 
         preSets.typeExpected = preSets.typeExpected || 'object';
@@ -126,10 +132,7 @@ export class CoreWSProvider {
      * @param method The WebService method to be called.
      * @param data Arguments to pass to the method.
      * @param preSets Extra settings and information. Only some
-     * @return Promise resolved with the response data in success and rejected with an object containing:
-     *         - error: Error message.
-     *         - errorcode: Error code returned by the site (if any).
-     *         - available: 0 if unknown, 1 if available, -1 if not available.
+     * @return Promise resolved with the response data in success and rejected with CoreAjaxError.
      */
     callAjax<T = unknown>(method: string, data: Record<string, unknown>, preSets: CoreWSAjaxPreSets): Promise<T> {
         const cacheParams = {
@@ -155,7 +158,7 @@ export class CoreWSProvider {
      * @param stripUnicode If Unicode long chars need to be stripped.
      * @return The cleaned object or null if some strings becomes empty after stripping Unicode.
      */
-    // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     convertValuesToString(data: any, stripUnicode?: boolean): any {
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         const result: any = Array.isArray(data) ? [] : {};
@@ -232,8 +235,12 @@ export class CoreWSProvider {
      * @param onProgress Function to call on progress.
      * @return Promise resolved with the downloaded file.
      */
-    async downloadFile(url: string, path: string, addExtension?: boolean, onProgress?: (event: ProgressEvent) => void):
-            Promise<CoreWSDownloadedFileEntry> {
+    async downloadFile(
+        url: string,
+        path: string,
+        addExtension?: boolean,
+        onProgress?: (event: ProgressEvent) => void,
+    ): Promise<CoreWSDownloadedFileEntry> {
         this.logger.debug('Downloading file', url, path, addExtension);
 
         if (!CoreApp.instance.isOnline()) {
@@ -249,7 +256,7 @@ export class CoreWSProvider {
             const fileEntry = await CoreFile.instance.createFile(tmpPath);
 
             const transfer = FileTransfer.instance.create();
-            transfer.onProgress(onProgress);
+            onProgress && transfer.onProgress(onProgress);
 
             // Download the file in the tmp file.
             await transfer.download(url, fileEntry.toURL(), true);
@@ -257,7 +264,7 @@ export class CoreWSProvider {
             let extension = '';
 
             if (addExtension) {
-                extension = CoreMimetypeUtils.instance.getFileExtension(path);
+                extension = CoreMimetypeUtils.instance.getFileExtension(path) || '';
 
                 // Google Drive extensions will be considered invalid since Moodle usually converts them.
                 if (!extension || CoreArray.contains(['gdoc', 'gsheet', 'gslides', 'gdraw', 'php'], extension)) {
@@ -281,14 +288,15 @@ export class CoreWSProvider {
             }
 
             // Move the file to the final location.
-            const movedEntry: CoreWSDownloadedFileEntry = await CoreFile.instance.moveFile(tmpPath, path);
+            const movedEntry = await CoreFile.instance.moveFile(tmpPath, path);
 
-            // Save the extension.
-            movedEntry.extension = extension;
-            movedEntry.path = path;
             this.logger.debug(`Success downloading file ${url} to ${path} with extension ${extension}`);
 
-            return movedEntry;
+            // Also return the extension and path.
+            return <CoreWSDownloadedFileEntry> Object.assign(movedEntry, {
+                extension: extension,
+                path: path,
+            });
         } catch (error) {
             this.logger.error(`Error downloading ${url} to ${path}`, error);
 
@@ -303,7 +311,7 @@ export class CoreWSProvider {
      * @param url Base URL of the HTTP request.
      * @param params Params of the HTTP request.
      */
-    protected getPromiseHttp<T = unknown>(method: string, url: string, params?: Record<string, unknown>): Promise<T> {
+    protected getPromiseHttp<T = unknown>(method: string, url: string, params?: Record<string, unknown>): Promise<T> | undefined {
         const queueItemId = this.getQueueItemId(method, url, params);
         if (typeof this.ongoingCalls[queueItemId] != 'undefined') {
             return this.ongoingCalls[queueItemId];
@@ -317,12 +325,14 @@ export class CoreWSProvider {
      * @param ignoreCache True to ignore cache, false otherwise.
      * @return Promise resolved with the mimetype or '' if failure.
      */
-    getRemoteFileMimeType(url: string, ignoreCache?: boolean): Promise<string> {
+    async getRemoteFileMimeType(url: string, ignoreCache?: boolean): Promise<string> {
         if (this.mimeTypeCache[url] && !ignoreCache) {
-            return Promise.resolve(this.mimeTypeCache[url]);
+            return this.mimeTypeCache[url]!;
         }
 
-        return this.performHead(url).then((response) => {
+        try {
+            const response = await this.performHead(url);
+
             let mimeType = response.headers.get('Content-Type');
             if (mimeType) {
                 // Remove "parameters" like charset.
@@ -331,10 +341,10 @@ export class CoreWSProvider {
             this.mimeTypeCache[url] = mimeType;
 
             return mimeType || '';
-        }).catch(() =>
+        } catch (error) {
             // Error, resolve with empty mimetype.
-            '',
-        );
+            return '';
+        }
     }
 
     /**
@@ -345,17 +355,15 @@ export class CoreWSProvider {
      */
     getRemoteFileSize(url: string): Promise<number> {
         return this.performHead(url).then((response) => {
-            const size = parseInt(response.headers.get('Content-Length'), 10);
+            const contentLength = response.headers.get('Content-Length');
+            const size = contentLength ? parseInt(contentLength, 10) : 0;
 
             if (size) {
                 return size;
             }
 
             return -1;
-        }).catch(() =>
-            // Error, return -1.
-            -1,
-        );
+        }).catch(() => -1);
     }
 
     /**
@@ -389,19 +397,16 @@ export class CoreWSProvider {
      * @param method The WebService method to be called.
      * @param data Arguments to pass to the method.
      * @param preSets Extra settings and information. Only some
-     * @return Promise resolved with the response data in success and rejected with an object containing:
-     *         - error: Error message.
-     *         - errorcode: Error code returned by the site (if any).
-     *         - available: 0 if unknown, 1 if available, -1 if not available.
+     * @return Promise resolved with the response data in success and rejected with CoreAjaxError.
      */
     protected performAjax<T = unknown>(method: string, data: Record<string, unknown>, preSets: CoreWSAjaxPreSets): Promise<T> {
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         let promise: Promise<HttpResponse<any>>;
 
         if (typeof preSets.siteUrl == 'undefined') {
-            return Promise.reject(new CoreAjaxError(Translate.instance.instant('core.unexpectederror')));
+            throw new CoreAjaxError(Translate.instance.instant('core.unexpectederror'));
         } else if (!CoreApp.instance.isOnline()) {
-            return Promise.reject(new CoreAjaxError(Translate.instance.instant('core.networkerrormsg')));
+            throw new CoreAjaxError(Translate.instance.instant('core.networkerrormsg'));
         }
 
         if (typeof preSets.responseExpected == 'undefined') {
@@ -446,23 +451,23 @@ export class CoreWSProvider {
 
             // Check if error. Ajax layer should always return an object (if error) or an array (if success).
             if (!data || typeof data != 'object') {
-                return Promise.reject(new CoreAjaxError(Translate.instance.instant('core.serverconnection')));
+                throw new CoreAjaxError(Translate.instance.instant('core.serverconnection'));
             } else if (data.error) {
-                return Promise.reject(new CoreAjaxWSError(data));
+                throw new CoreAjaxWSError(data);
             }
 
             // Get the first response since only one request was done.
             data = data[0];
 
             if (data.error) {
-                return Promise.reject(new CoreAjaxWSError(data.exception));
+                throw new CoreAjaxWSError(data.exception);
             }
 
             return data.data;
         }, (data) => {
             const available = data.status == 404 ? -1 : 0;
 
-            return Promise.reject(new CoreAjaxError(Translate.instance.instant('core.serverconnection'), available));
+            throw new CoreAjaxError(Translate.instance.instant('core.serverconnection'), available);
         });
     }
 
@@ -522,7 +527,7 @@ export class CoreWSProvider {
             }
 
             if (!data) {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.serverconnection')));
+                throw new CoreError(Translate.instance.instant('core.serverconnection'));
             } else if (typeof data != preSets.typeExpected) {
                 // If responseType is text an string will be returned, parse before returning.
                 if (typeof data == 'string') {
@@ -531,7 +536,7 @@ export class CoreWSProvider {
                         if (isNaN(data)) {
                             this.logger.warn(`Response expected type "${preSets.typeExpected}" cannot be parsed to number`);
 
-                            return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                            throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
                         }
                     } else if (preSets.typeExpected == 'boolean') {
                         if (data === 'true') {
@@ -541,17 +546,17 @@ export class CoreWSProvider {
                         } else {
                             this.logger.warn(`Response expected type "${preSets.typeExpected}" is not true or false`);
 
-                            return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                            throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
                         }
                     } else {
                         this.logger.warn('Response of type "' + typeof data + `" received, expecting "${preSets.typeExpected}"`);
 
-                        return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                        throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
                     }
                 } else {
                     this.logger.warn('Response of type "' + typeof data + `" received, expecting "${preSets.typeExpected}"`);
 
-                    return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                    throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
                 }
             }
 
@@ -561,11 +566,11 @@ export class CoreWSProvider {
                     this.logger.error('Error calling WS', method, data);
                 }
 
-                return Promise.reject(new CoreWSError(data));
+                throw new CoreWSError(data);
             }
 
             if (typeof data.debuginfo != 'undefined') {
-                return Promise.reject(new CoreError('Error. ' + data.message));
+                throw new CoreError('Error. ' + data.message);
             }
 
             return data;
@@ -593,7 +598,7 @@ export class CoreWSProvider {
                 return retryPromise;
             }
 
-            return Promise.reject(new CoreError(Translate.instance.instant('core.serverconnection')));
+            throw new CoreError(Translate.instance.instant('core.serverconnection'));
         });
     }
 
@@ -606,7 +611,7 @@ export class CoreWSProvider {
             const call = this.retryCalls.shift();
             // Add a delay between calls.
             setTimeout(() => {
-                call.deferred.resolve(this.performPost(call.method, call.siteUrl, call.data, call.preSets));
+                call!.deferred.resolve(this.performPost(call!.method, call!.siteUrl, call!.data, call!.preSets));
                 this.processRetryQueue();
             }, 200);
         } else {
@@ -623,8 +628,12 @@ export class CoreWSProvider {
      * @param params Params of the HTTP request.
      * @return The promise saved.
      */
-    protected setPromiseHttp<T = unknown>(promise: Promise<T>, method: string, url: string, params?: Record<string, unknown>):
-            Promise<T> {
+    protected setPromiseHttp<T = unknown>(
+        promise: Promise<T>,
+        method: string,
+        url: string,
+        params?: Record<string, unknown>,
+    ): Promise<T> {
         const queueItemId = this.getQueueItemId(method, url, params);
 
         this.ongoingCalls[queueItemId] = promise;
@@ -652,7 +661,7 @@ export class CoreWSProvider {
      * @return Promise resolved with the response data in success and rejected with the error message if it fails.
      * @return Request response.
      */
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any, @typescript-eslint/explicit-module-boundary-types
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
     syncCall<T = unknown>(method: string, data: any, preSets: CoreWSPreSets): T {
         if (!preSets) {
             throw new CoreError(Translate.instance.instant('core.unexpectederror'));
@@ -728,22 +737,26 @@ export class CoreWSProvider {
      * @param onProgress Function to call on progress.
      * @return Promise resolved when uploaded.
      */
-    uploadFile<T = unknown>(filePath: string, options: CoreWSFileUploadOptions, preSets: CoreWSPreSets,
-            onProgress?: (event: ProgressEvent) => void): Promise<T> {
+    async uploadFile<T = unknown>(
+        filePath: string,
+        options: CoreWSFileUploadOptions,
+        preSets: CoreWSPreSets,
+        onProgress?: (event: ProgressEvent) => void,
+    ): Promise<T> {
         this.logger.debug(`Trying to upload file: ${filePath}`);
 
         if (!filePath || !options || !preSets) {
-            return Promise.reject(new CoreError('Invalid options passed to upload file.'));
+            throw new CoreError('Invalid options passed to upload file.');
         }
 
         if (!CoreApp.instance.isOnline()) {
-            return Promise.reject(new CoreError(Translate.instance.instant('core.networkerrormsg')));
+            throw new CoreError(Translate.instance.instant('core.networkerrormsg'));
         }
 
         const uploadUrl = preSets.siteUrl + '/webservice/upload.php';
         const transfer = FileTransfer.instance.create();
 
-        transfer.onProgress(onProgress);
+        onProgress && transfer.onProgress(onProgress);
 
         options.httpMethod = 'POST';
         options.params = {
@@ -755,45 +768,51 @@ export class CoreWSProvider {
         options.headers = {};
         options['Connection'] = 'close';
 
-        return transfer.upload(filePath, uploadUrl, options, true).then((success) => {
-            const data = CoreTextUtils.instance.parseJSON(success.response, null,
-                this.logger.error.bind(this.logger, 'Error parsing response from upload', success.response));
+        try {
+            const success = await transfer.upload(filePath, uploadUrl, options, true);
+
+            // eslint-disable-next-line @typescript-eslint/no-explicit-any
+            const data = CoreTextUtils.instance.parseJSON<any>(
+                success.response,
+                null,
+                this.logger.error.bind(this.logger, 'Error parsing response from upload', success.response),
+            );
 
             if (data === null) {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
             }
 
             if (!data) {
-                return Promise.reject(new CoreError(Translate.instance.instant('core.serverconnection')));
+                throw new CoreError(Translate.instance.instant('core.serverconnection'));
             } else if (typeof data != 'object') {
                 this.logger.warn('Upload file: Response of type "' + typeof data + '" received, expecting "object"');
 
-                return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
+                throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
             }
 
             if (typeof data.exception !== 'undefined') {
-                return Promise.reject(new CoreWSError(data));
+                throw new CoreWSError(data);
             } else if (typeof data.error !== 'undefined') {
-                return Promise.reject(new CoreWSError({
+                throw new CoreWSError({
                     errorcode: data.errortype,
                     message: data.error,
-                }));
+                });
             } else if (data[0] && typeof data[0].error !== 'undefined') {
-                return Promise.reject(new CoreWSError({
+                throw new CoreWSError({
                     errorcode: data[0].errortype,
                     message: data[0].error,
-                }));
+                });
             }
 
             // We uploaded only 1 file, so we only return the first file returned.
             this.logger.debug('Successfully uploaded file', filePath);
 
             return data[0];
-        }).catch((error) => {
+        } catch (error) {
             this.logger.error('Error while uploading file', filePath, error);
 
-            return Promise.reject(new CoreError(Translate.instance.instant('core.errorinvalidresponse')));
-        });
+            throw new CoreError(Translate.instance.instant('core.errorinvalidresponse'));
+        }
     }
 
     /**
@@ -842,7 +861,7 @@ export class CoreWSProvider {
 
                 return new HttpResponse<T>({
                     body: <T> content,
-                    headers: null,
+                    headers: undefined,
                     status: 200,
                     statusText: 'OK',
                     url,
@@ -890,7 +909,7 @@ export class CoreWSProvider {
                     break;
 
                 default:
-                    return Promise.reject(new CoreError('Method not implemented yet.'));
+                    throw new CoreError('Method not implemented yet.');
             }
 
             if (angularOptions.timeout) {
@@ -966,6 +985,11 @@ export type CoreWSExternalWarning = {
  * Structure of files returned by WS.
  */
 export type CoreWSExternalFile = {
+    /**
+     * Downloadable file url.
+     */
+    fileurl: string;
+
     /**
      * File name.
      */
@@ -981,11 +1005,6 @@ export type CoreWSExternalFile = {
      */
     filesize?: number;
 
-    /**
-     * Downloadable file url.
-     */
-    fileurl?: string;
-
     /**
      * Time modified.
      */
@@ -1108,7 +1127,7 @@ export type HttpRequestOptions = {
     /**
      * Timeout for the request in seconds. If undefined, the default value will be used. If null, no timeout.
      */
-    timeout?: number | null;
+    timeout?: number;
 
     /**
      * Serializer to use. Defaults to 'urlencoded'. Only for mobile environments.
@@ -1162,6 +1181,6 @@ type RetryCall = {
  * Downloaded file entry. It includes some calculated data.
  */
 export type CoreWSDownloadedFileEntry = FileEntry & {
-    extension?: string; // File extension.
-    path?: string; // File path.
+    extension: string; // File extension.
+    path: string; // File path.
 };
diff --git a/src/app/singletons/array.ts b/src/app/singletons/array.ts
index 1e3da6b62..7f31bafc7 100644
--- a/src/app/singletons/array.ts
+++ b/src/app/singletons/array.ts
@@ -41,7 +41,7 @@ export class CoreArray {
             return (arr as any).flat(); // eslint-disable-line @typescript-eslint/no-explicit-any
         }
 
-        return [].concat(...arr);
+        return (<T[]> []).concat(...arr);
     }
 
     /**
diff --git a/src/app/singletons/locutus.ts b/src/app/singletons/locutus.ts
index 8f11cc7a1..c39484399 100644
--- a/src/app/singletons/locutus.ts
+++ b/src/app/singletons/locutus.ts
@@ -5,7 +5,7 @@
  */
 
 function initCache () {
-  const store = []
+  const store: any[] = []
   // cache only first element, second is length to jump ahead for the parser
   const cache = function cache (value) {
     store.push(value[0])
@@ -316,7 +316,7 @@ function expectArrayItems (str, expectedItems = 0, cache) {
   let hasStringKeys = false
   let item
   let totalOffset = 0
-  let items = []
+  let items: any[] = []
   cache([items])
 
   for (let i = 0; i < expectedItems; i++) {
diff --git a/src/app/singletons/url.ts b/src/app/singletons/url.ts
index d17af5bc6..3cb945572 100644
--- a/src/app/singletons/url.ts
+++ b/src/app/singletons/url.ts
@@ -141,7 +141,7 @@ export class CoreUrl {
         // If nothing else worked, parse the domain.
         const urlParts = CoreUrl.parse(url);
 
-        return urlParts && urlParts.domain ? urlParts.domain : null;
+        return urlParts?.domain ? urlParts.domain : null;
     }
 
     /**
@@ -196,8 +196,8 @@ export class CoreUrl {
         const partsA = CoreUrl.parse(urlA);
         const partsB = CoreUrl.parse(urlB);
 
-        return partsA.domain == partsB.domain &&
-                CoreTextUtils.instance.removeEndingSlash(partsA.path) == CoreTextUtils.instance.removeEndingSlash(partsB.path);
+        return partsA?.domain == partsB?.domain &&
+            CoreTextUtils.instance.removeEndingSlash(partsA?.path) == CoreTextUtils.instance.removeEndingSlash(partsB?.path);
     }
 
 }
diff --git a/src/app/singletons/window.ts b/src/app/singletons/window.ts
index 59b6542e6..c3a5762e2 100644
--- a/src/app/singletons/window.ts
+++ b/src/app/singletons/window.ts
@@ -60,7 +60,7 @@ export class CoreWindow {
 
             await CoreUtils.instance.openFile(url);
         } else {
-            let treated: boolean;
+            let treated = false;
             // eslint-disable-next-line @typescript-eslint/no-unused-vars
             options = options || {};
 
@@ -76,7 +76,7 @@ export class CoreWindow {
                     // Not logged in, cannot auto-login.
                     CoreUtils.instance.openInBrowser(url);
                 } else {
-                    await CoreSites.instance.getCurrentSite().openInBrowserWithAutoLoginIfSameSite(url);
+                    await CoreSites.instance.getCurrentSite()!.openInBrowserWithAutoLoginIfSameSite(url);
                 }
             }
         }