Do time machine backups retain OS version/compatibility?

[dj95]

I am currently on Catalina and time machine is backing that up. If I create a backup in Catalina prior to installing Big Sur and if I were to use Big Sur and in time create a Big Sur backup after install, can I still use the pre-Big Sur backup to restore back to Catalina backup (including Catalina OS)? I know I couldn’t restore the Big Sur backup to Catalina, but would that Catalina backup be ‘frozen’ in time and usable to revert back if needed, even if the backup disk contains a newer Big Sur backup?

 

[gilby101]

Big Sur will continue to do backups to your current TM destination. But that is a recipe for problems if you need to go back to full recovery of Catalina. With BS betas I did do a recovery to Catalina from a TM disk with both Catalina and BS backups - I was severely restricted as to which Catalina backup I could recover.

I suggest you get a new disk for BS backups. Failing that, if you have the space, create a new partition on your backup disk and tell BS's Time Machine to use that.

 

[chinchillas]

Did you use TM while using Big Sur? Don't do it if you want to use your latest Catalina backup!
You can clone Big Sur in a different drive just to make sure you don't lose any data. https://setapp.com/how-to/downgrade-from-big-sur-to-catalina