After updating the Mastodon app on your phone or desktop, you may see a red banner that reads “Sync Failed” at the top of your home timeline. This error means the app cannot refresh your feed, fetch new notifications, or post toots. The root cause is usually an expired authentication token or a corrupted local cache that the new app version cannot read. This article explains why the sync breaks after an update and provides three proven methods to restore normal operation.
Key Takeaways: Fixing Mastodon Sync Failed After Update
- Settings > Account > Clear Cache: Removes corrupted temporary files that block the sync handshake.
- Settings > Account > Log Out and Log In: Forces the app to request a fresh OAuth token from your instance server.
- Reinstall the App: Wipes all stored data including stale tokens and database corruption that a simple cache clear may miss.
Why the Sync Fails After Updating the Mastodon App
Mastodon apps store an OAuth access token locally after you log in. This token proves to your instance server that the app is allowed to read and post on your behalf. When the app updates, the new version may change how it stores or reads that token. If the token format is incompatible or the app cannot decrypt it, the server rejects the sync request and returns a 401 or 403 error.
A second common cause is a corrupted local cache. The Mastodon app caches timelines, notifications, and media thumbnails to speed up loading. An update can introduce a new database schema that the old cache files cannot match. The app then fails to read the cache and aborts the sync operation.
Server-Side Changes That Break Sync
Occasionally, your Mastodon instance administrator updates the server software. If the server now requires a newer API version or a stricter authentication header, the outdated app token may stop working. In that case, the sync failure appears after the app update simply because you noticed it then, but the real cause is the server change.
Steps to Fix Mastodon Sync Failed After Update
Try these methods in the order shown. Each method is more thorough than the previous one. Stop when the sync works again.
Method 1: Clear the App Cache
- Open Mastodon app settings
Tap your profile icon in the bottom-right corner of the home screen. Then tap the gear icon in the top-right corner to open Settings. - Navigate to Account settings
In the Settings menu, scroll down and tap Account. - Tap Clear Cache
Look for the Clear Cache button near the bottom of the Account screen. Tap it. A confirmation dialog appears. Tap OK or Clear. - Restart the app
Force-close the Mastodon app completely. On Android, swipe it away from the Recent Apps list. On iOS, double-tap the Home button and swipe up on the app. On desktop, click File > Exit or close the window. Reopen Mastodon and check if the red sync banner disappears.
Method 2: Log Out and Log In Again
- Go to Settings > Account
Tap your profile icon, then the gear icon, then Account. - Tap Log Out
Scroll to the bottom of the Account screen and tap Log Out. Confirm the action when prompted. - Close the app completely
Force-close Mastodon using your device’s app switcher. - Reopen Mastodon and log in
Launch the app again. On the login screen, enter your instance domain (for example, mastodon.social) and tap Continue. Sign in with your email and password. Authorize the app if your instance shows an OAuth consent screen. - Wait for the initial sync
The app will download your timelines and notifications from scratch. This may take 10 to 30 seconds. The “Sync Failed” banner should be gone.
Method 3: Reinstall the Mastodon App
- Uninstall the Mastodon app
On Android, long-press the app icon and tap Uninstall. On iOS, long-press the icon and tap Remove App then Delete App. On desktop, go to Settings > Apps > Apps & features, find Mastodon, and click Uninstall. - Restart your device
Power off your phone or computer completely, wait 10 seconds, and turn it back on. This step ensures no leftover app data remains in memory. - Install the latest Mastodon app version
Open your device’s app store (Google Play, Apple App Store, or Microsoft Store). Search for Mastodon and tap Install or Get. - Log in to your account
Open the freshly installed app. Enter your instance domain and credentials. Authorize the app as needed. The sync should work immediately.
If Mastodon Still Shows Sync Failed After the Main Fix
App Version Mismatch With Server API
Some older Mastodon instances run server software that does not support the latest API endpoints. If your instance is version 3.x and the app requires API version 4.x, sync will fail regardless of cache clearing. Check your instance version by visiting your profile page on the web and looking at the footer. If it shows a version below 4.0, contact your instance admin about upgrading or consider moving to a newer instance.
Third-Party App Sync Failures
If you use a third-party Mastodon client like Tusky, Fedilab, or Ivory, the sync failure may be caused by the app not being updated for the latest Mastodon API changes. Visit the app’s official website or support channel to see if a newer version is available. If no update exists, switch back to the official Mastodon app temporarily.
Network Proxy or VPN Blocking Sync
A VPN or corporate proxy can interfere with the WebSocket connection that Mastodon uses for real-time updates. Disable your VPN temporarily and test the sync. If the error disappears, add your Mastodon instance domain to the VPN’s bypass list or switch to a different VPN server.
Mastodon Official App vs Third-Party Client: Sync Reliability
| Item | Official Mastodon App | Third-Party Client |
|---|---|---|
| Sync after update | Usually works after clearing cache or relogin | May require waiting for client update to match API changes |
| Token storage | Uses system keychain or encrypted app storage | Varies by app; some store tokens in plain text files |
| Cache clearing | Built-in clear cache button in settings | May require clearing app data from device settings |
| Reinstall needed | Rarely needed; relogin usually sufficient | More common due to incompatible database schemas |
Clearing the app cache is the fastest fix and works in most cases. Logging out and logging in again resolves token-related failures. Reinstalling the app is the fallback for persistent corruption. If the problem continues, check your instance version and network environment before contacting support.