Although they can only grow in size, and mustn’t be left lying around, snapshots can be very useful, provided you manage them carefully, as described here.
tmutil
Snapshots made by Time Machine and tmutil should be purgeable, although sometimes they won’t purge, and aren’t shown reliably as purgeable space. An exploration of bugs and missing documentation.
Demonstrated 10 years ago as a major new feature in APFS, and capable of blazingly fast rollback preserving data including document versions, snapshots still aren’t fully accessible or documented.
Can be a Mac-saver if you have problems when your backup storage isn’t available. You don’t need to run Time Machine to make them, and can roll back in Recovery, as shown here.
When and how to use Migration Assistant to move apps, settings and documents to a new or previously owned Mac. Also how a Mac can claim an old Mac’s backups.
How to back up all your iCloud Drive documents, minimise snapshot size, keep integrity checks in important files, and more.
What is Time Machine best at doing? What are its current limitations in macOS Sonoma, when backing up to APFS? A draft list.
Good space management doesn’t bring new emoji, but it makes a big difference when the Finder doesn’t give completely inaccurate figures for Available space. A practical demonstration of its gross errors.
For many users, it’s essential to be able to check the integrity of the data which are in a backup. This feature has changed when backing up to APFS.
When your backups are stored on hard disks, even though they may use APFS, it’s important to check they’re sound. How to do better than Disk Utility.
The Eclectic Light Company 