When you sign in two different "desktop" installations of Firefox (on Windows, Mac, or Linux), their data gets merged. Unfortunately, I'm not aware of any quick way to "unmerge" them. The first step would be to sign one of the installations of Firefox out of your account (and keep it signed out). Then: (1) Bookmark Rollback Check whether you have a recent automatic backup you can restore to roll your bookmarks back. See: [[Restore bookmarks from backup or move them to another computer]] (2) Password Detangling As far as I know, there's no similar way to roll back merged passwords. You'll need to manually delete the unwanted ones.