Hi bruce18, I don't know whether MacOS keeps old data or backups when you update the system. I'll leave that question for the Mac experts. Did you ever create a Firefox Account and set up Sync on your Firefox? That would provide the possibility of connecting to that account again to retrieve data. It's not guaranteed, but any other copies of your data would be purely local to your system. More info on connecting your new Firefox to Sync: * [[How do I set up Sync on my computer?]] IMPORTANT: Do not reset your Sync password.