How to Free Up Purgeable Space on a Mac
Short answer
Purgeable space is mostly local Time Machine snapshots and cached iCloud files that macOS deletes automatically when the disk fills. To clear it now, run tmutil deletelocalsnapshots / in Terminal — only if you have a real external backup. Copying a large file to the disk also forces macOS to reclaim it. In most cases purgeable space is not a problem and needs no action.
On this page
A Mac reports 300GB free in one place and 180GB free in another. Hovering over the difference produces the word purgeable, with no explanation and no button.
Purgeable space is storage holding data macOS considers disposable. It is still occupied, but the moment anything needs the room, macOS deletes the contents without asking. Which means that for most purposes it already counts as free, and the common instinct to clear it urgently is wasted effort.
What is in it
| Contents | Typical size | Why it is purgeable |
|---|---|---|
| Local Time Machine snapshots | 10-150GB | macOS thins them under pressure |
| Cached iCloud Drive files | 1-50GB | Re-downloadable from iCloud |
| Optimised Photos originals | 5-100GB | Full versions live in iCloud |
| Watched Apple TV purchases | 1-20GB | Re-downloadable |
| App and system caches | 1-15GB | Regenerated on demand |
Local snapshots dominate on most Macs. They are taken hourly against the boot volume whenever Time Machine is enabled, regardless of whether a backup drive is connected, and they are the reason a Mac that has never been backed up still carries sixty gigabytes of purgeable data.
Decide whether you need to do anything
Three situations justify forcing it to clear. Everything else does not.
- An installer or app refuses to run, saying there is not enough space. Some software reads the raw free-space figure rather than asking macOS what is available, and sees the smaller number.
- You are about to clone, image or resize the disk. Disk Utility and third-party imaging tools generally want real free space.
- Finder genuinely will not accept a file. Rare, and usually a sign that free space is low for other reasons too.
If none of those apply, the honest answer is to leave it. macOS is holding useful data — recovery points and cached files — and reclaiming it only means re-downloading things later.
Clear local snapshots
This is the lever with the largest effect. Open Terminal (Applications → Utilities → Terminal):
tmutil listlocalsnapshots /You get a dated list. Each entry is a point you could restore a file from. To remove them all:
tmutil deletelocalsnapshots /Only run that if you have a real Time Machine backup on an external drive or network destination. Local snapshots are a genuine recovery mechanism, and deleting them means a file you removed by accident this morning cannot be brought back.
To delete a single dated snapshot instead, pass its date string from the list rather than the volume. That is the safer option when you want room now but not at the cost of every restore point.
Snapshots return within the hour if Time Machine stays enabled. That is the design, not a failure of the command.
Force macOS to reclaim it
The supported mechanism is pressure. macOS reclaims purgeable space when something needs it, so the way to trigger reclamation is to need something.
Copying a very large file to the disk works. So does starting a large download, or beginning a macOS update, which stages several gigabytes before installing. Watch Storage Settings and you will see purgeable space fall as the copy progresses.
A restart helps at the margins, clearing swap and temporary files and prompting a thinning pass. Expect a few gigabytes rather than tens.
Reduce the iCloud contribution
Cached iCloud content is purgeable because the original is safe in iCloud. Two settings control how much of it sits locally.
- Photos → Settings → iCloud: Optimise Mac Storage keeps smaller local versions and purgeable cached originals. Download Originals keeps everything locally, which reduces purgeable space and increases used space, so it rarely helps.
- System Settings → Apple Account → iCloud → iCloud Drive: Optimise Mac Storage does the same for Desktop and Documents.
In Finder you can right-click a folder in iCloud Drive and choose the option to remove its local download, which frees its space immediately and leaves the cloud copy intact. Useful for a project folder you have finished with.
What not to do
- Do not use a cleaner app for this. Snapshot deletion is the bulk of what
they recover, and
tmutildoes it free in one line. - Do not turn Time Machine off purely to stop snapshots, unless another backup exists. The number improves; your recovery position gets worse.
- Do not delete files from
/.MobileBackupsor similar hidden paths found in old forum posts. That mechanism predates APFS snapshots and the paths no longer mean what those posts assume. - Do not repeat the exercise weekly. Purgeable space regenerating is correct behaviour.
Realistic expectations
On a typical Mac, clearing snapshots takes purgeable space from somewhere around forty or sixty gigabytes down to near zero, and it climbs back over the following days. The free-space figure in Finder rises to match Storage Settings for a while, which is the main visible result.
If you came here because the disk is genuinely full rather than because two numbers disagreed, purgeable space is a side issue. What to do when the startup disk is almost full deals with the real occupants, and what sits inside System Data covers the categories macOS refuses to itemise.