If you want to downgrade to Big Sur from Ventura, is backing up necessary?

[levmc]

Would you end up losing all data if you didn't backup before downgrading? (I might not have enough space in my external drive to back it up completely, because I have a lot of files saved adding up and eating up a lot of storage space.)

 

[Absrnd]

You should always have a good backup, no matter what.
there is always a chance something doesn't go the way you expect, and you might end up losing important data.

If you don't want to spend cash for a new HD, you can always temporarily get some large iCloud storage.

 

[haralds]

You will not be allowed to install Big Sur over any newer macOS. Depending on how much space you have you can install BigSur on another volume from a USB installer or wipe the disk and start over with the USB Installer.

• I would make sure to have a backup on another disk.
• You will not be able to use the Migration Assistant, either.
• You will be able to copy most of your documents and drag installable apps.
• In some cases, it might also be possible to copy items from ~/Library/Application Support
• macOS apps databases cannot be opened:
  • You will need to import Photos from the Photos folder
  • You will need to import Music and Videos from their respective Media folders.
  • If you use iCloud, Notes, Calendars, and Mail should just download again.