apsolution27, this has come up before and unfortunately I don't think that there is no recovery of data that has been deleted from the Sync server. However, you might be able to recover data that still exists in local files, Although it is best to attempt this sooner rather than later. ---- you might be able to restore bookmarks from Firefox's own backups. See the "Restoring from backups" section here: https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them If that doesn't help, here's something else to try: https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update ---- Also, sometimes missing passwords can be retrieved using the logins-backup.json file in the Profile folder on the hard drive. If you do not know where your Profile folder is, see here: https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data To attempt password recovery: # open your Profile folder on the hard drive # close Firefox if it is running # move logins.json to a backup folder # copy logins-backup.json to a backup folder # in the profile folder, rename logins-backup.json to logins.json # restart Firefox If this doesn't work then you can always exit Firefox and then restore the original two files.