Glossary

Local snapshot

A local snapshot is a point-in-time record of your disk that macOS keeps on the disk itself, mainly for Time Machine. It can hold on to space from files you've since deleted.

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A local snapshot is a saved, point-in-time record of your Mac's disk that macOS keeps on the disk itself. Time Machine makes them so it has a steady picture of your files to back up, and so recent versions are at hand even when your backup drive isn't.

A snapshot keeps every file as it was when it was taken. So if you delete or move a file afterwards, the space it used isn't given back until the snapshot is removed. macOS removes local snapshots on its own after a while, or sooner when it needs space — which is why their space counts as purgeable.

Storage Studio's Local Snapshots… item in the More menu opens a window that lists them, shows how much space they're holding and whether a Time Machine backup exists, and lets you delete one or release space. If no Time Machine backup is set up, it warns you that the snapshots are the only copy of that state.

See also: Local snapshots · Storage Studio and Time Machine · APFS

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How do I reclaim space from local Time Machine snapshots on a Mac?
macOS keeps point-in-time APFS local snapshots so Time Machine can restore even when your backup drive is away — useful, but they can hold a lot of space. Storage Studio lists every snapshot, shows which are already safely backed up, and reclaims the space you choose in one click.
Can I move my iPhone backups to an external drive on a Mac?
Yes. Finder has no setting for where it keeps iPhone and iPad backups, but Storage Studio can move them to your external drive from What's Using Space: it copies them, checks every file arrived, and only then frees the space on your Mac. Finder keeps backing up to the drive afterwards, so keep…
What is purgeable space on a Mac and how do I clear it?
Purgeable space is storage macOS is holding — old snapshots, cached cloud files, optimised media — that it frees automatically when you need room, which is why "free" space can look smaller than expected. Storage Studio reclaims a lot of it on demand instead of making you wait.

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