There is no history on sync. [[Back up and restore information in Firefox profiles]] {web link} I use a Legacy add-on that makes backups of my user profile, Just In Case. Unfortunately, it is not compatible with the current Firefox. Every now and then, open the profile folder and create a '''copy''' of the current profile '''as is''' to another location on your hard drive. This way you will have a backup. If you do this each day, you will not lose much data. This should be done with '''Firefox Closed. ''' Note: In case you need to restore from these backups, you may need to overwrite old or corrupted files.