Back up and restore information in Firefox profiles.{web link} I use an 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.

Is Firefox running when you make this backup?

I think that Firefox locks some files in the profile folder when Firefox is running, so this backup utility might not be able to access these files. Firefox also keeps some data in memory when it is running and writes this to disk when you close Firefox and that is another reason that applications like Firefox should be closed when a backup is created. If this still happens when Firefox is closed then this might be a problem with other (security) software and not a real Firefox problem.