Firefox Sync allows you to sync your bookmarks, logins and passwords, browsing history, tab settings and other items across various devices. See How do I set up Sync on my computer? to learn more about how to turn on Sync.

You can disable Sync, if you like, to avoid syncing your data across certain devices when creating or signing in to your Mozilla account. You'll remain signed in to your account even after Sync has been disabled, unless you decide to sign out. You can also disable Sync for devices that have been synced previously. For additional information, see Remove a synced device from your Mozilla account.

Disable Sync for previously synced devices

To disable Sync for previously synced devices:

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.
2. Click Sync from the menu options to open the Sync settings panel.
3. Click the Change… button in the Syncing: ON subsection.

   The Choose What To Sync pop-up will open.

   

4. Click Disconnect… A confirmation prompt will appear.

   

5. Click the Disconnect button in the prompt.

This Firefox profile will stop syncing your account but won’t delete any data or settings. The Sync panel of your Firefox Settings page will now show Syncing: OFF.