I installed Tor on my Windows 7 PC in parrallel to Firefox. Both products can be run at the same time without any problem. My intention is to uninstall Firefox once I am Sure that Tor can be used without any problem. In order to reach this goal I decided first to Sync the Tor browser with the existing Firefox. Unfortunately although my Sync UserID and Password are accepted and with the message telling me that the Tor browser sync would start shortly nothing happens except an error message that I translate from the French to English: "Sync met an error during the synchronisation: Unknown error. Sync will try the operation again automatically."

That error seems to be a permanent error because I still have it after 1 hour or so.

2 Answers 2


It is likely that one of the items you are trying to sync is causing the sync to fail. You can check the log for an error which you get to by typing about:sync-log into the address bar.

An alternative solution would be to backup all of your settings and import them into the Tor browser. To do this open your browser and press ctrl+shift+b, then locate "Import and Backup" near the top.


I also noticed that sync feature doesn't always work. Adjusting security level might be helpful. But people think it might be harmful: https://trac.torproject.org/projects/tor/ticket/16488#comment:5

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