About Time Machine local snapshots
Time Machine lets you restore files from local snapshots of the files on your Mac, even when your Time Machine backup disk isn't available.
Your Time Machine backup disk might not always be available, so Time Machine also stores some of its backups on your Mac. These are local snapshots.
How to use local snapshots
When your backup disk isn't available, Time Machine automatically uses local snapshots to help you restore files. Reconnect your backup disk to make even more backups available.
How often local snapshots are saved
Time Machine saves one snapshot of your startup disk approximately every hour, and keeps it for 24 hours. It keeps an additional snapshot of your last successful Time Machine backup until space is needed. And in macOS High Sierra or later, another snapshot is saved before installing any macOS update.
How local snapshots use storage space
You don't need to think about how much storage space local snapshots are using, because they don't use space needed for tasks like downloading files, copying files, or installing new software. In fact, your Mac counts the space used by snapshots as available storage.
Even so, Time Machine stores snapshots only on disks that have plenty of free space, and it automatically deletes snapshots as they age or as space is needed for other things.
If you want to delete local snapshots manually, turn off automatic backups temporarily:
Open Time Machine settings:
Choose Time Machine settings (or preferences) from thein the menu bar.
Or in macOS Ventura or later, choose Apple menu > System Settings, click General in the sidebar, then click Time Machine on the right.
Or in macOS Monterey or earlier, choose Apple menu > System Preferences, then click Time Machine.
Turn off automatic backups in Time Machine settings:
In macOS Ventura or later, click Options, choose Manually from the "Back up frequency" pop-up menu, then click Done.
In macOS Monterey or earlier, deselect ”Back Up Automatically," or use the Off/On switch, depending on what you see.
Wait a few minutes to allow local snapshots to be deleted. Then turn on automatic backups again. Time Machine remembers the backup disks it was using.