Time Machine manages backups by creating snapshots that allow you to look back over time to select versions of documents, apps, folders, or other items that were later deleted or changed. Snapshots have a twofold purpose:
They seem to represent all the files on the disk so you can browse the structure you know.
They are compact but contain only the differences between the current state of your macOS boot volume and the last set of files saved. The first snapshot is, in fact, a full backup; those that follow, partial.
For some users, these snapshots may grow out of control. Readers regularly type in and ask how they can get rid of snapshots that fill their starting volume, making their system almost useless. I’ve provided answers in previous columns, such as “How to delete Time Machine snapshots on your Mac” and “How to fix your mysterious Mac storage problem.”
If you had a modern Mac, one running the APFS file system, Apple started introducing in macOS 10.12 Sierra, and backed up to an APFS-formatted Time Machine volume, you had few tools at your disposal as Apple relied on a different approach with its long-running HFS + file system.
With macOS Monterey, the Apple Disk Utility updated the app and its command-line counterpart to help manage APFS snapshots, whether created by Time Machine, Carbon Copy Cloner, or other software.
You can view snapshots by following these steps in Monterey with Disk Utility version 21:
Launch Applications> Utilities> Disk Utility.
Select your start volume in the left sidebar; with Catalina or later, select the volume group, labeled “volume”.
Choose View> View APFS snapshots.
At the bottom of the volume view, you can see all the snapshots made for that volume. Double-click a snapshot and it will mount in the Finder as a browsable volume. This can be much easier than using Time Machine to find a given set of older files.
You can select any snapshot and click the – (minus) button below the list to delete it. Warning! This is irreversible.
For a little more information in the list, click the… (More) button and select Show columns> Private size. This reflects the actual space that the snapshot takes up on the drive. This is in contrast to “Tidemark”, a term that Apple apparently does not define anywhere, but which seems to be the total storage space required for the entire set of files for the drive, not just those represented in the snapshot .
(Howard Oakley of Eclectic Light originally documented this solution, and credit was tipped for it by someone else. Visit his article for more technical details, including how to use command line options with tmutil.
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