Storage · free up space
What is purgeable space on a Mac?
Purgeable space is storage that is in use now but that macOS is willing to give back the moment an app needs room: local Time Machine snapshots, iCloud Drive files that are also in the cloud, and caches apps have marked as disposable. Finder and Storage settings count it as free; Terminal does not. You rarely need to free it yourself, and some of it cannot be freed at all.
Why two places disagree about your free space
Finder, Storage settings and the App Store ask macOS how much room there is for something important, and macOS answers with the space that is actually empty plus everything it could clear to make room. Terminal's df reports only the space that is empty right now. The gap between the two is purgeable space.
On the Mac this site is built on, on 29 October 2026, with macOS 26.5: df said3.4 GB free, and macOS said 4.1 GB was available for important use. So 0.7 GB was purgeable. That is typical of a Mac that is nearly full: macOS has already cleared most of what it was allowed to, which is exactly when the purgeable figure stops helping.
What purgeable space is made of
- Local Time Machine snapshots that macOS has marked purgeable. Time Machine keeps hourly snapshots on the startup disk while the backup drive is away.
- iCloud Drive and Photos originals that are already in iCloud, when Optimize Mac Storage is on. macOS can delete the local copy and download it again when you open it.
- Caches apps have marked disposable, which macOS may clear without asking the app.
One kind of snapshot is never purgeable: the one macOS makes for a system update. On the Mac above the only local snapshot was of that kind, marked Purgeable: No, so no command would have freed it. It goes when macOS decides it is no longer needed.
Seeing it yourself
df -H /
diskutil apfs listSnapshots /
tmutil listlocalsnapshots /The first line is the space that is really empty. The other two list local snapshots, anddiskutil says against each one whether it is purgeable. Compare the first figure with what Finder shows as available for the disk, and the difference is roughly what macOS could clear.
Freeing it, if you really need to
Usually you do not: a big download or an update asks for room and macOS makes it. When something refuses to start for lack of space anyway, these are the levers, safest first:
- Connect your Time Machine drive and let a backup finish. Snapshots that have been backed up are the first to go.
- Thin the purgeable snapshots with
tmutil thinlocalsnapshots / 999999999999 4. It removes only snapshots macOS has marked purgeable, and you lose the ability to roll back to those points without your backup drive. - Turn on Optimize Mac Storage for iCloud Drive and Photos, so older originals can live in iCloud only.
- Free real space instead. Purgeable space is often a few gigabytes; caches, developer data and old downloads are usually tens. See how to free up space on a Mac and what System Data is, where purgeable space is also counted.
Where the app comes in
RefreshYourMac shows the free space macOS really has, and adds the larger figure that includes purgeable space beside it when the two differ by more than half a gigabyte, so you can see how much of your free space is a promise. Its maintenance jobs count how many local snapshots are actually purgeable before offering to thin them, and say so when the answer is none. Everything it measures is rated by its safety levels before anything is deleted.
What to do next: see these numbers for your own Mac. Download RefreshYourMac free, or get it on the Mac App Store.
What it costs to have an app do this
| RefreshYourMac | CleanMyMac | MacKeeper | |
|---|---|---|---|
| Pay once | €119.95 on MacPaw’s store; $89.99 for CleanMyMac X on the Mac App Store | subscription only | |
| Yearly | $39.99/yr; €19.91/yr for the cleaning-only Essential Trio | €71.40 for the first year, 1 Mac. Their page shows it against a €119.40 list price | |
| Account needed | No | Yes | Yes |
Before you pay anything, both versions give you 3 free scans, and the download cleans your first 2 GB free. CleanMyMac and MacKeeper prices read from their own pages and the Mac App Store on 27 October 2026; the full comparison is at RefreshYourMac vs CleanMyMac and MacKeeper.
Frequently asked questions
Why does Finder show more free space than Terminal?
Finder asks macOS how much room there is for something important, and macOS answers with the space that is actually empty plus everything it could clear to make room. Terminal’s df reports only the space that is empty right now. The gap between the two is purgeable space.
What is purgeable space made of?
Local Time Machine snapshots that macOS has marked purgeable, iCloud Drive and Photos originals that are already in iCloud when Optimize Mac Storage is on, and caches apps have marked disposable.
How do I free purgeable space on a Mac?
Usually you do not have to: macOS clears it when an app asks for room. If something refuses to start anyway, let a Time Machine backup finish, thin the purgeable snapshots with tmutil thinlocalsnapshots, or turn on Optimize Mac Storage. Freeing real space, such as caches and old downloads, usually gives back far more.
Why can’t I delete a local snapshot?
Snapshots macOS makes for a system update are marked not purgeable, and no command frees them. On the Mac this guide was measured on, the only local snapshot was of that kind. It goes when macOS decides it is no longer needed.