Sync allows you to sync your bookmarks, logins and browsing information across different devices. When you're no longer using a device, you can remove it from your account and delete its associated browsing information if you choose.

1. Open Firefox on the computer you want to disconnect.
2. Click the menu button and choose Options.Preferences.
3. Click Firefox Account on the left panel.
4. Click the Disconnect button. A prompt will ask you if you want to clear your sync'ed data from that device.
5. Put a checkmark next to the information you want to remove, if any.