diff --git a/src/core/classes/base-sync.ts b/src/core/classes/base-sync.ts
new file mode 100644
index 000000000..4f7c1b63f
--- /dev/null
+++ b/src/core/classes/base-sync.ts
@@ -0,0 +1,307 @@
+// (C) Copyright 2015 Moodle Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// 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 { CoreApp } from '@services/app';
+import { CoreSites } from '@services/sites';
+import { CoreSync } from '@services/sync';
+import { CoreTextUtils } from '@services/utils/text';
+import { CoreTimeUtils } from '@services/utils/time';
+import { Translate } from '@singletons';
+import { CoreLogger } from '@singletons/logger';
+import { CoreError } from '@classes/errors/error';
+
+/**
+ * Blocked sync error.
+ */
+export class CoreSyncBlockedError extends CoreError {}
+
+/**
+ * Base class to create sync providers. It provides some common functions.
+ */
+export class CoreSyncBaseProvider<T = void> {
+
+    /**
+     * Logger instance.
+     */
+    protected logger: CoreLogger;
+
+    /**
+     * Component of the sync provider.
+     */
+    component = 'core';
+
+    /**
+     * Sync provider's interval.
+     */
+    syncInterval = 300000;
+
+    // Store sync promises.
+    protected syncPromises: { [siteId: string]: { [uniqueId: string]: Promise<T> } } = {};
+
+    constructor(component: string) {
+        this.logger = CoreLogger.getInstance(component);
+        this.component = component;
+    }
+
+    /**
+     * Add an offline data deleted warning to a list of warnings.
+     *
+     * @param warnings List of warnings.
+     * @param component Component.
+     * @param name Instance name.
+     * @param error Specific error message.
+     */
+    protected addOfflineDataDeletedWarning(warnings: string[], component: string, name: string, error: string): void {
+        const warning = Translate.instance.instant('core.warningofflinedatadeleted', {
+            component: component,
+            name: name,
+            error: error,
+        });
+
+        if (warnings.indexOf(warning) == -1) {
+            warnings.push(warning);
+        }
+    }
+
+    /**
+     * Add an ongoing sync to the syncPromises list. On finish the promise will be removed.
+     *
+     * @param id Unique sync identifier per component.
+     * @param promise The promise of the sync to add.
+     * @param siteId Site ID. If not defined, current site.
+     * @return The sync promise.
+     */
+    async addOngoingSync(id: string | number, promise: Promise<T>, siteId?: string): Promise<T> {
+        siteId = siteId || CoreSites.instance.getCurrentSiteId();
+
+        if (!siteId) {
+            throw new CoreError('CoreSyncBaseProvider: Site ID not supplied');
+        }
+
+        const uniqueId = this.getUniqueSyncId(id);
+        if (!this.syncPromises[siteId]) {
+            this.syncPromises[siteId] = {};
+        }
+
+        this.syncPromises[siteId][uniqueId] = promise;
+
+        // Promise will be deleted when finish.
+        try {
+            return await promise;
+        } finally {
+            delete this.syncPromises[siteId!][uniqueId];
+        }
+    }
+
+    /**
+     * If there's an ongoing sync for a certain identifier return it.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise of the current sync or undefined if there isn't any.
+     */
+    getOngoingSync(id: string | number, siteId?: string): Promise<T> | undefined {
+        siteId = siteId || CoreSites.instance.getCurrentSiteId();
+
+        if (!this.isSyncing(id, siteId)) {
+            return;
+        }
+
+        // There's already a sync ongoing for this id, return the promise.
+        const uniqueId = this.getUniqueSyncId(id);
+
+        return this.syncPromises[siteId][uniqueId];
+    }
+
+    /**
+     * Get the synchronization time in a human readable format.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved with the readable time.
+     */
+    async getReadableSyncTime(id: string | number, siteId?: string): Promise<string> {
+        const time = await this.getSyncTime(id, siteId);
+
+        return this.getReadableTimeFromTimestamp(time);
+    }
+
+    /**
+     * Given a timestamp return it in a human readable format.
+     *
+     * @param timestamp Timestamp
+     * @return Human readable time.
+     */
+    getReadableTimeFromTimestamp(timestamp: number): string {
+        if (!timestamp) {
+            return Translate.instance.instant('core.never');
+        } else {
+            return CoreTimeUtils.instance.userDate(timestamp);
+        }
+    }
+
+    /**
+     * Get the synchronization time. Returns 0 if no time stored.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved with the time.
+     */
+    async getSyncTime(id: string | number, siteId?: string): Promise<number> {
+        try {
+            const entry = await CoreSync.instance.getSyncRecord(this.component, id, siteId);
+
+            return entry.time;
+        } catch {
+            return 0;
+        }
+    }
+
+    /**
+     * Get the synchronization warnings of an instance.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved with the warnings.
+     */
+    async getSyncWarnings(id: string | number, siteId?: string): Promise<string[]> {
+        try {
+            const entry = await CoreSync.instance.getSyncRecord(this.component, id, siteId);
+
+            return  <string[]> CoreTextUtils.instance.parseJSON(entry.warnings, []);
+        } catch {
+            return [];
+        }
+    }
+
+    /**
+     * Create a unique identifier from component and id.
+     *
+     * @param id Unique sync identifier per component.
+     * @return Unique identifier from component and id.
+     */
+    protected getUniqueSyncId(id: string | number): string {
+        return this.component + '#' + id;
+    }
+
+    /**
+     * Check if a there's an ongoing syncronization for the given id.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Whether it's synchronizing.
+     */
+    isSyncing(id: string | number, siteId?: string): boolean {
+        siteId = siteId || CoreSites.instance.getCurrentSiteId();
+
+        const uniqueId = this.getUniqueSyncId(id);
+
+        return !!(this.syncPromises[siteId] && this.syncPromises[siteId][uniqueId]);
+    }
+
+    /**
+     * Check if a sync is needed: if a certain time has passed since the last time.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved with boolean: whether sync is needed.
+     */
+    async isSyncNeeded(id: string | number, siteId?: string): Promise<boolean> {
+        const time = await this.getSyncTime(id, siteId);
+
+        return Date.now() - this.syncInterval >= time;
+    }
+
+    /**
+     * Set the synchronization time.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @param time Time to set. If not defined, current time.
+     * @return Promise resolved when the time is set.
+     */
+    async setSyncTime(id: string, siteId?: string, time?: number): Promise<void> {
+        time = typeof time != 'undefined' ? time : Date.now();
+
+        await CoreSync.instance.insertOrUpdateSyncRecord(this.component, id, { time: time }, siteId);
+    }
+
+    /**
+     * Set the synchronization warnings.
+     *
+     * @param id Unique sync identifier per component.
+     * @param warnings Warnings to set.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved when done.
+     */
+    async setSyncWarnings(id: string, warnings: string[], siteId?: string): Promise<void> {
+        const warningsText = JSON.stringify(warnings || []);
+
+        await CoreSync.instance.insertOrUpdateSyncRecord(this.component, id, { warnings: warningsText }, siteId);
+    }
+
+    /**
+     * Execute a sync function on selected sites.
+     *
+     * @param syncFunctionLog Log message to explain the sync function purpose.
+     * @param syncFunction Sync function to execute.
+     * @param siteId Site ID to sync. If not defined, sync all sites.
+     * @return Resolved with siteIds selected. Rejected if offline.
+     */
+    async syncOnSites(syncFunctionLog: string, syncFunction: (siteId: string) => void, siteId?: string): Promise<void> {
+        if (!CoreApp.instance.isOnline()) {
+            const message = `Cannot sync '${syncFunctionLog}' because device is offline.`;
+            this.logger.debug(message);
+
+            throw new CoreError(message);
+        }
+
+        let siteIds: string[] = [];
+
+        if (!siteId) {
+            // No site ID defined, sync all sites.
+            this.logger.debug(`Try to sync '${syncFunctionLog}' in all sites.`);
+            siteIds = await CoreSites.instance.getLoggedInSitesIds();
+        } else {
+            this.logger.debug(`Try to sync '${syncFunctionLog}' in site '${siteId}'.`);
+            siteIds = [siteId];
+        }
+
+        // Execute function for every site.
+        await Promise.all(siteIds.map((siteId) => syncFunction(siteId)));
+    }
+
+    /**
+     * If there's an ongoing sync for a certain identifier, wait for it to end.
+     * If there's no sync ongoing the promise will be resolved right away.
+     *
+     * @param id Unique sync identifier per component.
+     * @param siteId Site ID. If not defined, current site.
+     * @return Promise resolved when there's no sync going on for the identifier.
+     */
+    async waitForSync(id: string | number, siteId?: string): Promise<T | undefined> {
+        const promise = this.getOngoingSync(id, siteId);
+
+        if (!promise) {
+            return;
+        }
+
+        try {
+            return await promise;
+        } catch {
+            return;
+        }
+    }
+
+}
diff --git a/src/core/features/user/services/handlers/sync-cron.ts b/src/core/features/user/services/handlers/sync-cron.ts
new file mode 100644
index 000000000..96a99cc17
--- /dev/null
+++ b/src/core/features/user/services/handlers/sync-cron.ts
@@ -0,0 +1,50 @@
+// (C) Copyright 2015 Moodle Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// 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 { CoreCronHandler } from '@services/cron';
+import { CoreUserSync } from '../user-sync';
+
+/**
+ * Synchronization cron handler.
+ */
+@Injectable({ providedIn: 'root' })
+export class CoreUserSyncCronHandler implements CoreCronHandler {
+
+    name = 'CoreUserSyncCronHandler';
+
+    /**
+     * Execute the process.
+     * Receives the ID of the site affected, undefined for all sites.
+     *
+     * @param siteId ID of the site affected, undefined for all sites.
+     * @param force Wether the execution is forced (manual sync).
+     * @return Promise resolved when done, rejected if failure.
+     */
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    execute(siteId?: string, force?: boolean): Promise<void> {
+        return CoreUserSync.instance.syncPreferences(siteId);
+    }
+
+    /**
+     * Get the time between consecutive executions.
+     *
+     * @return Time between consecutive executions (in ms).
+     */
+    getInterval(): number {
+        return 300000; // 5 minutes.
+    }
+
+}
diff --git a/src/core/features/user/services/user-sync.ts b/src/core/features/user/services/user-sync.ts
new file mode 100644
index 000000000..644c920ec
--- /dev/null
+++ b/src/core/features/user/services/user-sync.ts
@@ -0,0 +1,107 @@
+// (C) Copyright 2015 Moodle Pty Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// 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 { CoreSites } from '@services/sites';
+import { CoreTextUtils } from '@services/utils/text';
+import { CoreUtils } from '@services/utils/utils';
+import { CoreSyncBaseProvider } from '@classes/base-sync';
+import { makeSingleton } from '@singletons';
+import { CoreUserOffline } from './user-offline';
+import { CoreUser } from './user';
+
+/**
+ * Service to sync user preferences.
+ */
+@Injectable({ providedIn: 'root' })
+export class CoreUserSyncProvider extends CoreSyncBaseProvider<string[]> {
+
+    static readonly AUTO_SYNCED = 'core_user_autom_synced';
+
+    constructor() {
+        super('CoreUserSync');
+    }
+
+    /**
+     * Try to synchronize user preferences in a certain site or in all sites.
+     *
+     * @param siteId Site ID to sync. If not defined, sync all sites.
+     * @return Promise resolved with warnings if sync is successful, rejected if sync fails.
+     */
+    syncPreferences(siteId?: string): Promise<void> {
+        return this.syncOnSites('all user preferences', this.syncSitePreferences.bind(this), siteId);
+    }
+
+    /**
+     * Sync user preferences of a site.
+     *
+     * @param siteId Site ID to sync.
+     * @param Promise resolved with warnings if sync is successful, rejected if sync fails.
+     */
+    async syncSitePreferences(siteId: string): Promise<string[]> {
+        siteId = siteId || CoreSites.instance.getCurrentSiteId();
+
+        const syncId = 'preferences';
+
+        if (this.isSyncing(syncId, siteId)) {
+            // There's already a sync ongoing, return the promise.
+            return this.getOngoingSync(syncId, siteId)!;
+        }
+
+        this.logger.debug('Try to sync user preferences');
+
+        const syncPromise = this.performSyncSitePreferences(siteId);
+
+        return this.addOngoingSync(syncId, syncPromise, siteId);
+    }
+
+    /**
+     * Sync user preferences of a site.
+     *
+     * @param siteId Site ID to sync.
+     * @param Promise resolved if sync is successful, rejected if sync fails.
+     */
+    protected async performSyncSitePreferences(siteId: string): Promise<string[]> {
+        const warnings: string[] = [];
+
+        const preferences = await CoreUserOffline.instance.getChangedPreferences(siteId);
+
+        await CoreUtils.instance.allPromises(preferences.map(async (preference) => {
+            const onlineValue = await CoreUser.instance.getUserPreferenceOnline(preference.name, siteId);
+
+            if (onlineValue !== null && preference.onlinevalue != onlineValue) {
+                // Preference was changed on web while the app was offline, do not sync.
+                return CoreUserOffline.instance.setPreference(preference.name, onlineValue, onlineValue, siteId);
+            }
+
+            try {
+                await CoreUser.instance.setUserPreference(preference.name, preference.value, siteId);
+            } catch (error) {
+                if (CoreUtils.instance.isWebServiceError(error)) {
+                    warnings.push(CoreTextUtils.instance.getErrorMessageFromError(error)!);
+                } else {
+                    // Couldn't connect to server, reject.
+                    throw error;
+                }
+            }
+        }));
+
+        // All done, return the warnings.
+        return warnings;
+    }
+
+}
+
+export class CoreUserSync extends makeSingleton(CoreUserSyncProvider) {}
diff --git a/src/core/features/user/user.module.ts b/src/core/features/user/user.module.ts
index 6c580f42d..1a7190632 100644
--- a/src/core/features/user/user.module.ts
+++ b/src/core/features/user/user.module.ts
@@ -41,6 +41,13 @@ const routes: Routes = [
             ],
             multi: true,
         },
+        // { @todo: Uncomment when the init process has been fixed.
+        //     provide: APP_INITIALIZER,
+        //     multi: true,
+        //     deps: [CoreCronDelegate, CoreUserSyncCronHandler],
+        //     useFactory: (cronDelegate: CoreCronDelegate, syncHandler: CoreUserSyncCronHandler) =>
+        //         () => cronDelegate.register(syncHandler),
+        // },
     ],
 })
 export class CoreUserModule {}
diff --git a/src/core/services/sync.ts b/src/core/services/sync.ts
index 7c3c7ca22..84a22e8ef 100644
--- a/src/core/services/sync.ts
+++ b/src/core/services/sync.ts
@@ -112,7 +112,7 @@ export class CoreSyncProvider {
      * @param siteId Site ID. If not defined, current site.
      * @return Promise resolved with done.
      */
-    async insertOrUpdateSyncRecord(component: string, id: string, data: CoreSyncRecord, siteId?: string): Promise<void> {
+    async insertOrUpdateSyncRecord(component: string, id: string, data: Partial<CoreSyncRecord>, siteId?: string): Promise<void> {
         const db = await CoreSites.instance.getSiteDb(siteId);
 
         data.component = component;