diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 7f710b31b..546d1db53 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -69,7 +69,7 @@ jobs:
         cat circular-dependencies
         lines=$(cat circular-dependencies | wc -l)
         echo "Total circular dependencies: $lines"
-        test $lines -eq 130
+        test $lines -eq 90
     - name: JavaScript code compatibility
       run: |
         npx check-es-compat www/*.js --polyfills="\{Array,String,TypedArray\}.prototype.at,Object.hasOwn"
diff --git a/src/core/features/compile/services/compile.ts b/src/core/features/compile/services/compile.ts
index 8c9f316b9..688c75576 100644
--- a/src/core/features/compile/services/compile.ts
+++ b/src/core/features/compile/services/compile.ts
@@ -79,23 +79,30 @@ import { Md5 } from 'ts-md5/dist/md5';
 // Import core classes that can be useful for site plugins.
 import { CoreSyncBaseProvider } from '@classes/base-sync';
 import { CoreArray } from '@singletons/array';
+import { CoreCache } from '@classes/cache';
 import { CoreColors } from '@singletons/colors';
+import { CoreCountries } from '@singletons/countries';
+import { CoreDelegate } from '@classes/delegate';
 import { CoreDirectivesRegistry } from '@singletons/directives-registry';
 import { CoreDom } from '@singletons/dom';
+import { CoreFileUtils } from '@singletons/file-utils';
 import { CoreForms } from '@singletons/form';
+import { CoreGeolocationError, CoreGeolocationErrorReason } from '@services/geolocation';
 import { CoreKeyboard } from '@singletons/keyboard';
+import { CoreMedia } from '@singletons/media';
+import { CoreNetwork } from '@services/network';
 import { CoreObject } from '@singletons/object';
+import { CoreOpener } from '@singletons/opener';
 import { CorePath } from '@singletons/path';
+import { CorePromiseUtils } from '@singletons/promise-utils';
+import { CoreSSO } from '@singletons/sso';
 import { CoreText } from '@singletons/text';
 import { CoreTime } from '@singletons/time';
 import { CoreUrl } from '@singletons/url';
+import { CoreUtils } from '@singletons/utils';
 import { CoreWait } from '@singletons/wait';
 import { CoreWindow } from '@singletons/window';
-import { CoreCache } from '@classes/cache';
-import { CoreDelegate } from '@classes/delegate';
-import { CoreGeolocationError, CoreGeolocationErrorReason } from '@services/geolocation';
 import { getCoreErrorsExportedObjects } from '@classes/errors/errors';
-import { CoreNetwork } from '@services/network';
 
 // Import all core modules that define components, directives and pipes.
 import { CoreSharedModule } from '@/core/shared.module';
@@ -312,19 +319,26 @@ export class CoreCompileProvider {
          */
         instance['Network'] = CoreNetwork.instance;
         instance['CoreNetwork'] = CoreNetwork.instance;
-        instance['CorePlatform'] = CorePlatform.instance;
-        instance['CoreSyncBaseProvider'] = CoreSyncBaseProvider;
         instance['CoreArray'] = CoreArray;
         instance['CoreColors'] = CoreColors;
+        instance['CoreCountries'] = CoreCountries;
         instance['CoreDirectivesRegistry'] = CoreDirectivesRegistry;
         instance['CoreDom'] = CoreDom;
+        instance['CoreFileUtils'] = CoreFileUtils;
         instance['CoreForms'] = CoreForms;
         instance['CoreKeyboard'] = CoreKeyboard;
+        instance['CoreMedia'] = CoreMedia;
         instance['CoreObject'] = CoreObject;
+        instance['CoreOpener'] = CoreOpener;
         instance['CorePath'] = CorePath;
+        instance['CorePlatform'] = CorePlatform.instance;
+        instance['CorePromiseUtils'] = CorePromiseUtils;
+        instance['CoreSSO'] = CoreSSO;
+        instance['CoreSyncBaseProvider'] = CoreSyncBaseProvider;
         instance['CoreText'] = CoreText;
         instance['CoreTime'] = CoreTime;
         instance['CoreUrl'] = CoreUrl;
+        instance['CoreUtils'] = CoreUtils;
         instance['CoreWait'] = CoreWait;
         instance['CoreWindow'] = CoreWindow;
         instance['CoreCache'] = CoreCache; // @deprecated since 4.4, plugins should use plain objects instead.
diff --git a/src/core/singletons/browser.ts b/src/core/singletons/browser.ts
index 5ff1d3dde..30628431b 100644
--- a/src/core/singletons/browser.ts
+++ b/src/core/singletons/browser.ts
@@ -14,9 +14,16 @@
 
 /**
  * Helpers to interact with Browser APIs.
+ *
+ * This singleton is not necessary to be exported for site plugins.
  */
 export class CoreBrowser {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Check whether the given cookie is set.
      *
@@ -34,9 +41,9 @@ export class CoreBrowser {
      * @returns Whether the development setting is set.
      */
     static hasDevelopmentSetting(name: string): boolean {
-        const setting = this.getDevelopmentSettingKey(name);
+        const setting = CoreBrowser.getDevelopmentSettingKey(name);
 
-        return this.hasCookie(setting) || this.hasLocalStorage(setting);
+        return CoreBrowser.hasCookie(setting) || CoreBrowser.hasLocalStorage(setting);
     }
 
     /**
@@ -84,9 +91,9 @@ export class CoreBrowser {
      * @returns Development setting value.
      */
     static getDevelopmentSetting(name: string): string | null {
-        const setting = this.getDevelopmentSettingKey(name);
+        const setting = CoreBrowser.getDevelopmentSettingKey(name);
 
-        return this.getCookie(setting) ?? this.getLocalStorage(setting);
+        return CoreBrowser.getCookie(setting) ?? CoreBrowser.getLocalStorage(setting);
     }
 
     /**
@@ -96,7 +103,7 @@ export class CoreBrowser {
      * @param value Setting value.
      */
     static setDevelopmentSetting(name: string, value: string): void {
-        const setting = this.getDevelopmentSettingKey(name);
+        const setting = CoreBrowser.getDevelopmentSettingKey(name);
 
         document.cookie = `${setting}=${value};path=/`;
         localStorage.setItem(setting, value);
@@ -108,7 +115,7 @@ export class CoreBrowser {
      * @param name Setting name.
      */
     static clearDevelopmentSetting(name: string): void {
-        const setting = this.getDevelopmentSettingKey(name);
+        const setting = CoreBrowser.getDevelopmentSettingKey(name);
 
         document.cookie = `${setting}=;path=/;expires=Thu, 01 Jan 1970 00:00:01 GMT`;
         localStorage.removeItem(setting);
diff --git a/src/core/singletons/colors.ts b/src/core/singletons/colors.ts
index 806fffe74..8fdd18acc 100644
--- a/src/core/singletons/colors.ts
+++ b/src/core/singletons/colors.ts
@@ -42,6 +42,11 @@ export enum CoreIonicColorNames {
  */
 export class CoreColors {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Returns better contrast color.
      *
@@ -99,7 +104,7 @@ export class CoreColors {
         }
 
         const hex = [0,1,2].map(
-            (idx) => this.componentToHex(rgba[idx]),
+            (idx) => CoreColors.componentToHex(rgba[idx]),
         ).join('');
 
         return '#' + hex;
diff --git a/src/core/singletons/directives-registry.ts b/src/core/singletons/directives-registry.ts
index 50fc996b6..47e911571 100644
--- a/src/core/singletons/directives-registry.ts
+++ b/src/core/singletons/directives-registry.ts
@@ -32,9 +32,9 @@ export class CoreDirectivesRegistry {
      * @param instance Directive instance.
      */
     static register(element: Element, instance: unknown): void {
-        const list = this.instances.get(element) ?? [];
+        const list = CoreDirectivesRegistry.instances.get(element) ?? [];
         list.push(instance);
-        this.instances.set(element, list);
+        CoreDirectivesRegistry.instances.set(element, list);
     }
 
     /**
@@ -45,7 +45,7 @@ export class CoreDirectivesRegistry {
      * @returns Directive instance.
      */
     static resolve<T>(element?: Element | null, directiveClass?: DirectiveConstructor<T>): T | null {
-        const list = (element && this.instances.get(element) as T[]) ?? [];
+        const list = (element && CoreDirectivesRegistry.instances.get(element) as T[]) ?? [];
 
         return list.find(instance => !directiveClass || instance instanceof directiveClass) ?? null;
     }
@@ -58,7 +58,7 @@ export class CoreDirectivesRegistry {
      * @returns Directive instances.
      */
     static resolveAll<T>(element?: Element | null, directiveClass?: DirectiveConstructor<T>): T[] {
-        const list = (element && this.instances.get(element) as T[]) ?? [];
+        const list = (element && CoreDirectivesRegistry.instances.get(element) as T[]) ?? [];
 
         return list.filter(instance => !directiveClass || instance instanceof directiveClass) ?? [];
     }
@@ -71,7 +71,7 @@ export class CoreDirectivesRegistry {
      * @returns Directive instance.
      */
     static require<T>(element: Element, directiveClass?: DirectiveConstructor<T>): T {
-        const instance = this.resolve(element, directiveClass);
+        const instance = CoreDirectivesRegistry.resolve(element, directiveClass);
 
         if (!instance) {
             throw new Error('Couldn\'t resolve directive instance');
@@ -91,9 +91,9 @@ export class CoreDirectivesRegistry {
         element: Element | null,
         directiveClass?: DirectiveConstructor<T>,
     ): Promise<void> {
-        const instance = this.resolve(element, directiveClass);
+        const instance = CoreDirectivesRegistry.resolve(element, directiveClass);
         if (!instance) {
-            this.logger.error('No instance registered for element ' + directiveClass, element);
+            CoreDirectivesRegistry.logger.error('No instance registered for element ' + directiveClass, element);
 
             return;
         }
@@ -129,7 +129,7 @@ export class CoreDirectivesRegistry {
         }
 
         await Promise.all(elements.map(async element => {
-            const instances = this.resolveAll<T>(element, directiveClass);
+            const instances = CoreDirectivesRegistry.resolveAll<T>(element, directiveClass);
 
             await Promise.all(instances.map(instance => instance.ready()));
         }));
@@ -139,7 +139,7 @@ export class CoreDirectivesRegistry {
 
         // Check if there are new elements now that the found elements are ready (there could be nested elements).
         if (elements.length !== findElements().length) {
-            await this.waitDirectivesReady(element, selector, directiveClass);
+            await CoreDirectivesRegistry.waitDirectivesReady(element, selector, directiveClass);
         }
     }
 
@@ -174,7 +174,7 @@ export class CoreDirectivesRegistry {
             allElements = allElements.concat(elements);
 
             await Promise.all(elements.map(async element => {
-                const instances = this.resolveAll<AsyncDirective>(element, directive.class);
+                const instances = CoreDirectivesRegistry.resolveAll<AsyncDirective>(element, directive.class);
 
                 await Promise.all(instances.map(instance => instance.ready()));
             }));
@@ -191,7 +191,7 @@ export class CoreDirectivesRegistry {
         }, <Element[]> []);
 
         if (allElements.length !== elementsAfterReady.length) {
-            await this.waitMultipleDirectivesReady(element, directives);
+            await CoreDirectivesRegistry.waitMultipleDirectivesReady(element, directives);
         }
     }
 
diff --git a/src/core/singletons/dom.ts b/src/core/singletons/dom.ts
index 34a671a62..2e91e4124 100644
--- a/src/core/singletons/dom.ts
+++ b/src/core/singletons/dom.ts
@@ -512,7 +512,7 @@ export class CoreDom {
                     return resolve();
                 }
 
-                unsubscribe = this.watchElementInViewport(element, intersectionRatio, inViewport => {
+                unsubscribe = CoreDom.watchElementInViewport(element, intersectionRatio, inViewport => {
                     if (!inViewport) {
                         return;
                     }
@@ -632,7 +632,7 @@ export class CoreDom {
         const value = styles.getPropertyValue(property);
 
         if (property === 'font-size') {
-            if (this.fontSizeZoom === null) {
+            if (CoreDom.fontSizeZoom === null) {
                 const baseFontSize = 20;
                 const span = document.createElement('span');
                 span.style.opacity = '0';
@@ -640,13 +640,13 @@ export class CoreDom {
 
                 document.body.append(span);
 
-                this.fontSizeZoom = baseFontSize / Number(getComputedStyle(span).fontSize.slice(0, -2));
+                CoreDom.fontSizeZoom = baseFontSize / Number(getComputedStyle(span).fontSize.slice(0, -2));
 
                 span.remove();
             }
 
-            if (this.fontSizeZoom !== 1) {
-                return `calc(${this.fontSizeZoom} * ${value})`;
+            if (CoreDom.fontSizeZoom !== 1) {
+                return `calc(${CoreDom.fontSizeZoom} * ${value})`;
             }
         }
 
diff --git a/src/core/singletons/error-logs.ts b/src/core/singletons/error-logs.ts
index 8f828034b..f0b02c73b 100644
--- a/src/core/singletons/error-logs.ts
+++ b/src/core/singletons/error-logs.ts
@@ -11,24 +11,26 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-import { Injectable } from '@angular/core';
-import { makeSingleton } from '@singletons';
 
 /**
  * Service that stores error logs in memory.
  */
-@Injectable({ providedIn: 'root' })
-export class CoreErrorLogsService {
+export class CoreErrorLogs {
 
-    protected errorLogs: CoreSettingsErrorLog[] = [];
+    protected static errorLogs: CoreSettingsErrorLog[] = [];
+
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
 
     /**
      * Retrieve error logs displayed in the DOM.
      *
      * @returns Error logs
      */
-    getErrorLogs(): CoreSettingsErrorLog[] {
-        return this.errorLogs;
+    static getErrorLogs(): CoreSettingsErrorLog[] {
+        return CoreErrorLogs.errorLogs;
     }
 
     /**
@@ -36,14 +38,12 @@ export class CoreErrorLogsService {
      *
      * @param error Error.
      */
-    addErrorLog(error: CoreSettingsErrorLog): void {
-        this.errorLogs.push(error);
+    static addErrorLog(error: CoreSettingsErrorLog): void {
+        CoreErrorLogs.errorLogs.push(error);
     }
 
 }
 
-export const CoreErrorLogs = makeSingleton(CoreErrorLogsService);
-
 export type CoreSettingsErrorLog = {
     data?: unknown;
     message: string;
diff --git a/src/core/singletons/events.ts b/src/core/singletons/events.ts
index 53ec4d871..df42a0a96 100644
--- a/src/core/singletons/events.ts
+++ b/src/core/singletons/events.ts
@@ -122,6 +122,11 @@ export class CoreEvents {
     protected static observables: { [eventName: string]: Subject<unknown> } = {};
     protected static uniqueEvents: { [eventName: string]: {data: unknown} } = {};
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Listen for a certain event. To stop listening to the event:
      * let observer = eventsProvider.on('something', myCallBack);
@@ -140,8 +145,8 @@ export class CoreEvents {
     ): CoreEventObserver {
         // If it's a unique event and has been triggered already, call the callBack.
         // We don't need to create an observer because the event won't be triggered again.
-        if (this.uniqueEvents[eventName]) {
-            callBack(this.uniqueEvents[eventName].data as CoreEventData<Event, Fallback> & CoreEventSiteData);
+        if (CoreEvents.uniqueEvents[eventName]) {
+            callBack(CoreEvents.uniqueEvents[eventName].data as CoreEventData<Event, Fallback> & CoreEventSiteData);
 
             // Return a fake observer to prevent errors.
             return {
@@ -151,14 +156,14 @@ export class CoreEvents {
             };
         }
 
-        this.logger.debug(`New observer listening to event '${eventName}'`);
+        CoreEvents.logger.debug(`New observer listening to event '${eventName}'`);
 
-        if (this.observables[eventName] === undefined) {
+        if (CoreEvents.observables[eventName] === undefined) {
             // No observable for this event, create a new one.
-            this.observables[eventName] = new Subject();
+            CoreEvents.observables[eventName] = new Subject();
         }
 
-        const subscription = this.observables[eventName].subscribe(
+        const subscription = CoreEvents.observables[eventName].subscribe(
             (value: CoreEventData<Event, Fallback> & CoreEventSiteData) => {
                 if (!siteId || value.siteId == siteId) {
                     callBack(value);
@@ -169,7 +174,7 @@ export class CoreEvents {
         // Create and return a CoreEventObserver.
         return {
             off: (): void => {
-                this.logger.debug(`Stop listening to event '${eventName}'`);
+                CoreEvents.logger.debug(`Stop listening to event '${eventName}'`);
                 subscription.unsubscribe();
             },
         };
@@ -211,7 +216,7 @@ export class CoreEvents {
      * @returns Observer to stop listening.
      */
     static onMultiple<T = unknown>(eventNames: string[], callBack: (value: T) => void, siteId?: string): CoreEventObserver {
-        const observers = eventNames.map((name) => this.on<T>(name, callBack, siteId));
+        const observers = eventNames.map((name) => CoreEvents.on<T>(name, callBack, siteId));
 
         // Create and return a CoreEventObserver.
         return {
@@ -235,12 +240,12 @@ export class CoreEvents {
         data?: CoreEventData<Event, Fallback>,
         siteId?: string,
     ): void {
-        this.logger.debug(`Event '${eventName}' triggered.`);
-        if (this.observables[eventName]) {
+        CoreEvents.logger.debug(`Event '${eventName}' triggered.`);
+        if (CoreEvents.observables[eventName]) {
             if (siteId) {
                 Object.assign(data || {}, { siteId });
             }
-            this.observables[eventName].next(data || {});
+            CoreEvents.observables[eventName].next(data || {});
         }
     }
 
@@ -256,23 +261,23 @@ export class CoreEvents {
         data: CoreEventData<Event, Fallback>,
         siteId?: string,
     ): void {
-        if (this.uniqueEvents[eventName]) {
-            this.logger.debug(`Unique event '${eventName}' ignored because it was already triggered.`);
+        if (CoreEvents.uniqueEvents[eventName]) {
+            CoreEvents.logger.debug(`Unique event '${eventName}' ignored because it was already triggered.`);
         } else {
-            this.logger.debug(`Unique event '${eventName}' triggered.`);
+            CoreEvents.logger.debug(`Unique event '${eventName}' triggered.`);
 
             if (siteId) {
                 Object.assign(data || {}, { siteId });
             }
 
             // Store the data so it can be passed to observers that register from now on.
-            this.uniqueEvents[eventName] = {
+            CoreEvents.uniqueEvents[eventName] = {
                 data,
             };
 
             // Now pass the data to observers.
-            if (this.observables[eventName]) {
-                this.observables[eventName].next(data);
+            if (CoreEvents.observables[eventName]) {
+                CoreEvents.observables[eventName].next(data);
             }
         }
     }
@@ -283,7 +288,7 @@ export class CoreEvents {
      * @param eventName Event name.
      */
     static waitUntil(eventName: string): Promise<void> {
-        return new Promise(resolve => this.once(eventName, () => resolve()));
+        return new Promise(resolve => CoreEvents.once(eventName, () => resolve()));
     }
 
 }
diff --git a/src/core/singletons/form.ts b/src/core/singletons/form.ts
index 5cdc0d77c..80ccda79f 100644
--- a/src/core/singletons/form.ts
+++ b/src/core/singletons/form.ts
@@ -22,6 +22,11 @@ export class CoreForms {
 
     private static formIds: Record<string, number> = {};
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Get the data from a form. It will only collect elements that have a name.
      *
@@ -102,9 +107,9 @@ export class CoreForms {
      * @returns Unique id.
      */
     static uniqueId(name: string): string {
-        const count = this.formIds[name] ?? 0;
+        const count = CoreForms.formIds[name] ?? 0;
 
-        return `${name}-${this.formIds[name] = count + 1}`;
+        return `${name}-${CoreForms.formIds[name] = count + 1}`;
     }
 
 }
diff --git a/src/core/singletons/html-classes.ts b/src/core/singletons/html-classes.ts
index 9803f1e19..27b1ccaad 100644
--- a/src/core/singletons/html-classes.ts
+++ b/src/core/singletons/html-classes.ts
@@ -29,6 +29,11 @@ export class CoreHTMLClasses {
     protected static readonly MOODLEAPP_VERSION_PREFIX = 'moodleapp-';
     protected static readonly MOODLE_SITE_THEME_PREFIX = 'theme-site-';
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Initialize HTML classes.
      */
@@ -101,10 +106,10 @@ export class CoreHTMLClasses {
      */
     static addSiteClasses(siteInfo: CoreSiteInfo | CoreSiteInfoResponse): void {
         // Add version classes to html tag.
-        this.removeSiteClasses();
+        CoreHTMLClasses.removeSiteClasses();
 
-        this.addVersionClass(CoreHTMLClasses.MOODLE_VERSION_PREFIX, CoreSites.getReleaseNumber(siteInfo.release || ''));
-        this.addSiteUrlClass(siteInfo.siteurl);
+        CoreHTMLClasses.addVersionClass(CoreHTMLClasses.MOODLE_VERSION_PREFIX, CoreSites.getReleaseNumber(siteInfo.release || ''));
+        CoreHTMLClasses.addSiteUrlClass(siteInfo.siteurl);
 
         if (siteInfo.theme) {
             CoreHTMLClasses.toggleModeClass(CoreHTMLClasses.MOODLE_SITE_THEME_PREFIX + siteInfo.theme, true);
@@ -116,7 +121,7 @@ export class CoreHTMLClasses {
      */
     static removeSiteClasses(): void {
         // Remove version classes from html tag.
-        this.removeModeClasses(
+        CoreHTMLClasses.removeModeClasses(
             [
                 CoreHTMLClasses.MOODLE_VERSION_PREFIX,
                 CoreHTMLClasses.MOODLE_SITE_URL_PREFIX,
@@ -161,7 +166,7 @@ export class CoreHTMLClasses {
      * Convenience function to add site url to html classes.
      */
     static addSiteUrlClass(siteUrl: string): void {
-        const className = this.urlToClassName(siteUrl);
+        const className = CoreHTMLClasses.urlToClassName(siteUrl);
 
         CoreHTMLClasses.toggleModeClass(CoreHTMLClasses.MOODLE_SITE_URL_PREFIX + className, true);
     }
diff --git a/src/core/singletons/icons.ts b/src/core/singletons/icons.ts
index 2a49c7c28..de179372f 100644
--- a/src/core/singletons/icons.ts
+++ b/src/core/singletons/icons.ts
@@ -28,6 +28,11 @@ export class CoreIcons {
 
     protected static logger = CoreLogger.getInstance('CoreIcons');
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Add custom icons to Ionicons.
      */
@@ -47,7 +52,7 @@ export class CoreIcons {
 
         if (CoreIcons.ALIASES[icon]) {
             if (isAppIcon) {
-                this.logger.error(`Icon ${icon} is an alias of ${CoreIcons.ALIASES[icon]}, please use the new name.`);
+                CoreIcons.logger.error(`Icon ${icon} is an alias of ${CoreIcons.ALIASES[icon]}, please use the new name.`);
             }
 
             return { newLibrary, fileName: CoreIcons.ALIASES[icon] };
@@ -73,7 +78,7 @@ export class CoreIcons {
             CoreIcons.CUSTOM_ICONS[icon] === undefined &&
             CoreIcons.CUSTOM_ICONS[CoreIcons.prefixIconName(font, library, icon)] === undefined
         ) {
-            this.logger.error(`Icon ${icon} not found`);
+            CoreIcons.logger.error(`Icon ${icon} not found`);
         }
     }
 
diff --git a/src/core/singletons/keyboard.ts b/src/core/singletons/keyboard.ts
index bb44c0d43..2c3c01269 100644
--- a/src/core/singletons/keyboard.ts
+++ b/src/core/singletons/keyboard.ts
@@ -25,6 +25,11 @@ export class CoreKeyboard {
     protected static keyboardOpening = false;
     protected static keyboardClosing = false;
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Closes the keyboard.
      */
@@ -51,7 +56,7 @@ export class CoreKeyboard {
      */
     static onKeyboardShow(keyboardHeight: number): void {
         document.body.classList.add('keyboard-is-open');
-        this.setKeyboardShown(true);
+        CoreKeyboard.setKeyboardShown(true);
         // Error on iOS calculating size.
         // More info: https://github.com/ionic-team/ionic-plugin-keyboard/issues/276 .
         CoreEvents.trigger(CoreEvents.KEYBOARD_CHANGE, keyboardHeight);
@@ -62,7 +67,7 @@ export class CoreKeyboard {
      */
     static onKeyboardHide(): void {
         document.body.classList.remove('keyboard-is-open');
-        this.setKeyboardShown(false);
+        CoreKeyboard.setKeyboardShown(false);
         CoreEvents.trigger(CoreEvents.KEYBOARD_CHANGE, 0);
     }
 
diff --git a/src/core/singletons/math.ts b/src/core/singletons/math.ts
index af51906ae..d1bb2a9d6 100644
--- a/src/core/singletons/math.ts
+++ b/src/core/singletons/math.ts
@@ -17,6 +17,11 @@
  */
 export class CoreMath {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Clamp a value between a minimum and a maximum.
      *
diff --git a/src/core/singletons/subscriptions.ts b/src/core/singletons/subscriptions.ts
index b0cea166d..cb7acb873 100644
--- a/src/core/singletons/subscriptions.ts
+++ b/src/core/singletons/subscriptions.ts
@@ -26,6 +26,11 @@ type Subscribable<T> = EventEmitter<T> | Observable<T>;
  */
 export class CoreSubscriptions {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Listen once to a subscribable object.
      *
diff --git a/src/core/singletons/swiper.ts b/src/core/singletons/swiper.ts
index 46cb7bb3d..9dbf5ab7d 100644
--- a/src/core/singletons/swiper.ts
+++ b/src/core/singletons/swiper.ts
@@ -23,6 +23,11 @@ import { SwiperOptions } from 'swiper/types';
  */
 export class CoreSwiper {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Initialize a Swiper instance.
      * It will return swiper instance if current is not set or destroyed and new is set and not destroyed.
diff --git a/src/core/singletons/time.ts b/src/core/singletons/time.ts
index a1015828d..f647b02e4 100644
--- a/src/core/singletons/time.ts
+++ b/src/core/singletons/time.ts
@@ -78,6 +78,11 @@ export class CoreTime {
         '13.0': 'Etc/GMT-13',
     };
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Returns years, months, days, hours, minutes and seconds in a human readable format.
      *
diff --git a/src/core/singletons/wait.ts b/src/core/singletons/wait.ts
index 72e6c6ea8..b4d41bebe 100644
--- a/src/core/singletons/wait.ts
+++ b/src/core/singletons/wait.ts
@@ -20,6 +20,11 @@ import { CorePlatform } from '@services/platform';
  */
 export class CoreWait {
 
+    // Avoid creating singleton instances.
+    private constructor() {
+        // Nothing to do.
+    }
+
     /**
      * Wait until the next tick.
      *