Firefox Sync Has Stopped Working: Bookmarks and Passwords

Firefox sync not working — bookmarks, passwords, or open tabs not appearing across devices — is almost always an account authentication issue rather than a data problem. The data is usually fine; the connection between Firefox and Mozilla’s sync server needs refreshing. If you want the full context, see our Google Chrome Errors.

Check sync status first: Firefox menu → Settings → Sync → look at the status message. “Connected” with a green indicator means Firefox believes sync is working. “Sign in” means you’re logged out. An error message gives the specific reason. If you see “Connected” but data isn’t appearing: the connection is stale and needs a refresh. If there’s an error: the error message guides the specific fix.

Fix 1: Sign out and back in

The Firefox Account authentication token expires over time. Firefox may remain signed in visually but sync requests are silently rejected by Mozilla’s servers. Refreshing the token fixes this:

1. Firefox menu → Settings → Sync → click your account name → “Manage account” or “Sign out”
2. Sign out completely → close Firefox → reopen → Settings → Sync → Sign in
3. Complete any verification (email link or OTP) → sync should begin within 1-2 minutes

After signing back in: don’t immediately check for data — give sync 2-5 minutes to pull down from Mozilla’s servers, especially on a new device or after a long offline period.

Fix 2: Check what’s enabled to sync

Firefox syncs specific data types independently. Firefox menu → Settings → Sync → “Change what you sync” → each type (Bookmarks, Passwords, Open Tabs, History, Add-ons, Addresses, Payment methods, Preferences) has its own toggle. If a specific type isn’t syncing: confirm its toggle is On on both devices.

Common scenario: bookmarks sync on the desktop but not on mobile Firefox. Mobile Firefox → Menu → Settings → your account → Sync now → also check which data types are enabled in mobile settings. Mobile and desktop can have different sync configurations independently.

Fix 3: Sync conflict resolution

Firefox uses a “last write wins” approach for most sync conflicts. If the same bookmark was edited on two devices before either synced: the server keeps one version and discards the other. This looks like data loss but is actually conflict resolution. After initial conflict resolution: keep only one device making changes until the other device has synced.

For bookmarks specifically: if some bookmarks are missing after a sync conflict, check the “Unsorted Bookmarks” folder and the bookmarks from recent backup (Library → Bookmarks → Restore → Choose file → select a recent JSON backup).

Fix 4: Force sync on both devices

Firefox syncs on a schedule — typically every few minutes when active. To force an immediate sync on a device:

• Desktop: Firefox menu → Settings → Sync → “Sync now” button, or right-click the sync icon in the toolbar → “Sync”
• Mobile: Menu → Settings → your account → “Sync now”

Force sync on both devices → wait 60 seconds → check whether data appears. This resolves cases where the sync schedule hasn’t fired recently rather than the sync infrastructure being broken.

Fix 5: Data missing on a new device

When setting up Firefox on a new device and signed into Firefox Account: give sync 5-15 minutes before declaring data missing. The initial sync of a large bookmark collection, extensive browsing history, and many saved passwords takes time — particularly on slow connections.

If data still hasn’t appeared after 15 minutes: Firefox menu → Settings → Sync → “Sync now” → watch the sync icon spin → it should populate within the next 1-2 minutes. If it shows “Connected” but data never appears: the account may have empty cloud data (possible if sync was never enabled on the device that had the data, or if data was stored locally without sync).

Account data on Mozilla’s servers

Firefox sync stores data encrypted on Mozilla’s servers. To check what’s actually there: go to accounts.firefox.com → manage your account → scroll to “Connected devices” to see all devices syncing. If a device isn’t listed, it’s not part of the sync network even if it shows as signed in locally.

If you need to see the data on the server: you can’t directly read it (it’s encrypted client-side), but the “Disconnect” option for old devices prevents them from syncing stale data that overwrites newer data from current devices.

Sync and Firefox profiles

Firefox sync is per-profile. If you have multiple Firefox profiles: each needs to be signed in independently, and each syncs its own data independently. If bookmarks appear in one Firefox profile but not another on the same machine: the profiles have different Firefox Account associations or different sync settings. Open the Profile Manager (firefox.exe -ProfileManager) to manage multiple profiles.

Our guide on Firefox bookmark recovery covers the local backup and profile-based recovery when sync doesn’t contain the needed data. For Firefox performance issues that sometimes occur after sync loads large amounts of data, our Firefox startup troubleshooting covers the profile and database maintenance approach. Mozilla’s sync troubleshooting documentation covers the about:sync-log page that shows technical sync activity, the account recovery options, and how to reset the sync server data while preserving local data.

Firewall and network connectivity for sync

Firefox sync connects to sync.services.mozilla.com and accounts.firefox.com. Corporate firewalls or VPNs that block these domains prevent sync from working even when Firefox can browse the internet normally. Test: disconnect VPN → attempt sync. If sync works without VPN: the VPN was blocking the sync servers. Adding Mozilla’s sync servers to the VPN’s split tunnel exclusion list resolves this without compromising VPN security.

Passwords not syncing — specific notes

Firefox password sync requires “Passwords” to be enabled in sync settings on all devices. Beyond the toggle: Firefox also has an optional primary password (formerly Master Password) that encrypts the local password store. If a primary password is set on one device but not another: password sync between them may work inconsistently because the encryption keys differ.

Check: Firefox Settings → Privacy and Security → “Use a Primary Password” — if enabled on one device, the same primary password needs to be set on the syncing device for passwords to decrypt correctly. Alternatively: remove the primary password on both devices and let sync handle the encryption transparently.

Open tabs not appearing across devices

Firefox Sync’s open tab sharing requires the “Open Tabs” toggle in sync settings and the tab collection page in the Firefox sidebar. After enabling: the Synced Tabs section in Firefox → Library → Synced Tabs shows open tabs from other signed-in devices. If tabs from a specific device don’t appear: that device may have the “Open Tabs” toggle off, or it may not have synced recently (restart Firefox on the other device to force a sync cycle).

Mobile Firefox tabs appear in desktop Firefox’s Synced Tabs view, and vice versa. This is particularly useful for continuing mobile browsing on desktop — a common workflow that Firefox sync handles elegantly when configured correctly.

History sync limitations

Firefox syncs browsing history but with a limitation: only up to 60 days of history is synced by default. History older than this stays local to the device where it was created. If you’re looking for history from months ago: it exists on the original device’s local storage but wasn’t synced and won’t be available on other devices.

Also: Firefox doesn’t sync history from Private Browsing mode. History from private sessions exists only for the duration of that session and is never included in sync.

Add-ons sync — what it does and doesn’t do

Enabling “Add-ons” sync means Firefox installs the same extensions on all signed-in devices. Extension settings are not synced — each extension needs to be configured per device. This is by design: extension configurations often contain device-specific data (custom shortcuts, device-specific filter lists, local paths).

If an extension on one device has specific settings you want on another: most extensions have their own export/import function in their settings page. Use that to transfer the specific configuration rather than expecting sync to handle it.

Resetting sync data

If sync data on Mozilla’s servers has become corrupted or contains wrong data — for example, if an old device overwrote good data with bad data before being disconnected — you can reset the server-side data while keeping local data intact.

Firefox Settings → Sync → click account name → “Manage Account” → on the Mozilla Accounts website → scroll to “Delete data” → “Delete sync data.” After deleting: Firefox uploads fresh data from the local profile on the next sync. This should be done while logged in on the device whose local data is correct — that device becomes the authoritative source for the fresh server sync.

Firefox sync vs Lockwise

Mozilla previously had a separate app called Firefox Lockwise for password management. This has been discontinued and merged into Firefox itself. If you used Lockwise previously and passwords aren’t appearing in Firefox sync: they should have been migrated automatically. Check Firefox Settings → Privacy and Security → Saved passwords to see whether they’re there — they may have been imported without the sync toggle being enabled.

Debugging sync with about:sync-log

Navigate to about:sync-log in Firefox’s address bar to see the sync activity log. This shows every sync attempt, what data types were synced, and any errors encountered. Common log entries:

• “Sync Status: Starting” followed by “Sync Status: Finished” — successful sync cycle
• “Sync failed: Network error” — connectivity issue; check internet access
• “Sync failed: AuthenticationError” — token expired; sign out and back in
• “Uploading bookmarks” or “Downloading passwords” — confirms specific data types are active

The log is the most direct diagnostic tool for Firefox sync — it shows exactly what’s happening rather than just “sync is on/off.” If you can see error types in the log: the fix is targeted immediately.

Quick reference

Firefox sync is generally reliable when the account connection is healthy. Sign out/in resolves most failures, and the about:sync-log shows what’s happening when it doesn’t. The most important thing to know is that sync data is encrypted client-side — Firefox’s privacy-first approach means Mozilla can’t see your data, which also means Mozilla’s support can’t recover it if it’s lost. Keeping local backups (particularly of bookmarks via JSON export) supplements sync rather than relying on it as the only copy.

One practical consideration for users managing Firefox across multiple devices: Mozilla’s two-factor authentication for Firefox Accounts significantly reduces the risk of account compromise, which could otherwise result in someone else accessing your synced bookmarks and passwords. Enabling 2FA at accounts.firefox.com → Security → Two-step authentication protects the account even if the password is compromised, and it’s specifically important given that Firefox sync stores password vault data on Mozilla’s servers (even though it’s encrypted). The sign-in process with 2FA requires one extra step but is worth it for the account protection it provides.

If you switched from another browser and are looking for sync features comparable to Chrome-Google sync or Edge-Microsoft sync: Firefox sync covers the same categories (bookmarks, passwords, history, open tabs, settings) with the added privacy benefit of end-to-end encryption. The one area where Firefox sync has traditionally been less seamless: because the encryption means no server-side access to the data, the “I forgot which device had that bookmark” scenario can’t be resolved by contacting Mozilla support — the data lives in the encrypted vault, and only your Firefox account credentials (and primary password if set) unlock it. Keeping at least one device signed in and synced regularly ensures the data always has an accessible current copy.

For Firefox users transitioning from Chrome: the import process (Firefox Settings → Import browser data → Chrome) brings bookmarks, history, and saved passwords from Chrome into Firefox locally. After importing: enabling Firefox sync uploads that data to Mozilla’s servers, making it available on all your Firefox devices. This migration-then-sync workflow is the cleanest path to having all your browsing history and bookmarks available in Firefox across devices without any data loss during the transition. You might also run into Chrome Password Manager Not Working.

A final note: Firefox sync is reliable once configured, but it’s not a backup system. It’s a synchronisation system — which means deleting a bookmark on one device deletes it from the server and from all other devices. For true backup: use Firefox’s “Export bookmarks to HTML” or “Export to JSON” (Library → Bookmarks → Import and Backup → Export) and save the file to cloud storage separately. Sync keeps things consistent across devices; local exports preserve data against accidental deletion. Related: How to Fix Edge Sync Not Working.