When Firefox Sync stops updating, it usually looks like this: your phone shows old bookmarks or tabs, your desktop has newer ones, and nothing seems to “catch up.” The good news is you can often restart syncing without wiping your data.
Start on mobile first (it’s where background limits and account prompts cause the most silent failures), then do the desktop checks if needed.
If you’re worried about losing bookmarks or passwords: avoid “Remove Sync” or “Disconnect” until you’ve tried the safer steps below.
1. Mobile-first: confirm you’re signed into the same Firefox Account
Sync only works if every device is on the same Firefox Account email.
- iPhone/iPad: Firefox > Menu > Settings > your account (email at the top)
- Android: Firefox > Menu > Settings > Sync and save data (or Sign in)
If the email differs across devices, fix that first. It’s the #1 reason “Sync is on” but nothing matches.
2. Mobile-first: force a clean sync cycle (without disconnecting)
Mobile browsers can get stuck if the app hasn’t done a full foreground sync in a while.
- Open Firefox on your phone and leave it in the foreground for 30–60 seconds (don’t immediately switch apps).
- Pull-to-refresh a page, then open a new tab, then check Bookmarks—this nudges background tasks to run.
- Toggle sync items off/on (bookmarks, tabs, passwords) if Firefox shows per-item switches. This is safer than signing out.
Then check whether another device receives a small change (for example, create a test bookmark named “SYNC TEST”).
One tiny test change is better than guessing.
3. Mobile-first: remove common blockers (battery, data, VPN, time)
Sync can fail quietly when the phone prevents background networking or when device time is off.
- Battery restrictions: disable battery optimization for Firefox (Android) or Low Power Mode (iOS) temporarily, then try syncing again.
- Data restrictions: allow background data for Firefox (Android) and confirm Firefox can use cellular data (iOS Settings > Cellular).
- VPN/ad blocker/DNS apps: pause them for 2 minutes and test sync. Some block Firefox Account endpoints.
- Date & time: set to automatic. Incorrect time can break secure sign-in and token refresh.
If Sync starts working after pausing a VPN/DNS app, you’ve found the cause—re-enable it and add an exception if your tool supports it.
4. Desktop steps: confirm Sync is enabled and “last sync” is recent
Now switch to desktop to verify the sync chain from the “source of truth” device (often your main computer).
- Firefox (desktop) > Menu > Settings > Sync
- Make sure you’re signed in and that the right categories are enabled (Bookmarks, Logins and passwords, Tabs, History, Add-ons).
- Look for a “last synced” status. If it never updates, the desktop may be stuck too.
If only one category is failing (for example, tabs sync but passwords don’t), that’s a clue the issue is permissions, encryption, or a blocked endpoint—keep going.
This is also a good moment to update Firefox on desktop and mobile.
5. Desktop steps: do a safe reset of sync state (log out last)
If you’ve confirmed the same account everywhere and network/time are fine, try these in order:
- Restart Firefox on desktop (fully quit and reopen), then wait 1 minute with Firefox open.
- Disable/enable Sync from the Sync settings screen (if available) without removing the account.
- Temporarily disable extensions that filter traffic (privacy, security, script blockers) and test again.
- Only if still stuck: sign out of Sync on one device (start with the device that has the least “unique” data), then sign back in.
When you sign back in, choose the option that keeps local data if Firefox asks. If you see wording you’re unsure about, stop and back up bookmarks first.
6. If nothing changes: check for account/security prompts and server-side pauses
Sometimes Sync stops because the account needs attention.
- Look for a Firefox Account email about a new sign-in, password change, or suspicious activity.
- Try signing into your Firefox Account on the web to confirm it’s active and not locked.
- If you recently changed your Firefox Account password, give devices time to re-authenticate (and open Firefox on each device once).
If Sync works on Wi‑Fi but never on mobile data (or the reverse), your network is likely filtering something. In that case, the “fix” is usually a DNS/VPN setting change, not a Firefox setting.
Final thoughts
Most Firefox Sync stalls come down to one of three things: different account emails, mobile background/battery limits, or a network/VPN/DNS filter. Start mobile-first, make one small test change, and only sign out as a last step.
If you tell me whether you’re on iOS or Android and what exactly isn’t syncing (tabs vs bookmarks vs passwords), you can narrow this down fast.