Do you want to remove all data as to Firefox A? First, shut down the sync account. Delete Account: Look for '''Delete Account''' at the bottom of https://accounts.firefox.com/settings After, create a new sync using the system/profile that has the data. Wait for a while until the syncing is done before adding any new members. Note: On computer A, I suggest creating a new profile and to sync that. After, remove the old profile, unless there is something you want in it. ------------- [[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.