Freeing up space · Local snapshots and held space
Why can't I delete a snapshot marked Required?
Short answer: macOS needs it, usually for a system update, so it shows a Required pill and can't be deleted. It normally clears itself once that update is complete.
Because macOS needs it — usually for a system update. These snapshots show a grey Required pill instead of a Delete button and can't be removed, even with Delete all backed-up.
They normally go away by themselves once the update they belong to is complete. If you need space urgently in the meantime, other snapshots and the rest of your disk are still available to work with — see Custom reclaim.