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Purgeable space on a Mac: what it is and how to actually free it

You delete 40 GB of video, check your free space, and nothing changed — or Finder cheerfully claims you have 60 GB available while an app insists the disk is full. The culprit is purgeable space: storage macOS considers reclaimable but has not yet released. It is a real feature, not a bug, and understanding it is the difference between a five-minute fix and an afternoon of frustration.

Updated 2026-08-02 · Written by the CleanerMac team · macOS 13–15 tested

What purgeable space is

Purgeable space is disk currently occupied by data that macOS believes it can delete or re-download on demand, and will delete automatically if an app needs the room. Because macOS counts it as effectively available, Finder's “Available” figure often includes it — which is why the numbers you see can be misleading.

Four things typically make up purgeable space:

• APFS local snapshots. Time Machine takes hourly snapshots on your startup disk when the backup drive is not connected. A snapshot pins the old versions of every block, so files you deleted after the snapshot was taken are still physically present.
• iCloud-optimised files. Photos, documents and Messages attachments already uploaded to iCloud that macOS can evict locally at any moment.
• Caches macOS deems disposable — including streamed Music, TV and Podcasts content.
• Trash contents when Empty Trash Automatically is enabled.

Why APFS makes deletion feel delayed

APFS is a copy-on-write filesystem. When a snapshot exists, deleting a file does not release its blocks — it only removes the reference from the current filesystem view. The blocks stay allocated because the snapshot still points at them. They become free only when every snapshot referencing them is removed.

This is a genuinely good design: it is what makes Time Machine's local restore, safe system updates and instant rollbacks possible. But it explains the single most common Mac storage complaint — “I deleted things and got no space back.” You did delete them; a snapshot is simply still holding the blocks.

How to see the real numbers

Do not trust Finder's Get Info window or the Storage pane for this. Use Terminal:

• df -h / — actual free space on the volume, purgeable excluded from the used figure differently than Finder reports it. Compare it against what Finder claims and the gap is roughly your purgeable space.
• diskutil info / | grep -i "free\|available" — shows both container free space and volume available space; the difference between them is instructive.
• tmutil listlocalsnapshots / — lists every local snapshot with its timestamp. If this returns several entries, you have found your purgeable space.
• sudo du -sh /System/Volumes/Data/* 2>/dev/null — a top-level map of the data volume.

Forcing purgeable space to be released

macOS will free it automatically when something needs the room, but you often need it back on your terms. In order of effectiveness:

1. Thin local snapshots. Run sudo tmutil thinlocalsnapshots / 999999999999 4. The big number is a byte target meaning “reclaim as much as you can”; the 4 is the highest urgency level, which instructs macOS to delete rather than defer. Your Time Machine backups on the external drive are untouched. Re-check with df -h /.
2. Delete a specific snapshot. If you want surgical control, take a name from tmutil listlocalsnapshots / and run tmutil deletelocalsnapshots <snapshot-name>.
3. Empty the Trash — and Photos' Recently Deleted, and Mail's Trash mailbox.
4. Restart. A reboot clears swap and triggers macOS to re-evaluate purgeable data. Modest, but free.
5. Create pressure deliberately. Copying a very large file to the disk forces macOS to purge in order to make room, then you delete the large file. This works but is crude — prefer the tmutil route.
6. Disable Optimise Mac Storage temporarily if iCloud eviction is confusing your accounting, then re-enable it once you have a clear picture.

Purgeable versus genuinely free space

That last row causes real problems. Some installers, disk-image tools and virtualisation apps check the raw free-space figure and refuse to proceed even though macOS would happily purge space if they simply started writing. If an installer says there is not enough room while Finder says there is, thin your snapshots and try again.

When purgeable space is a symptom of something bigger

A few gigabytes of purgeable space is entirely normal. Tens of gigabytes usually means snapshots have been accumulating for weeks because the Time Machine drive has not been connected, or that an app is churning through large temporary files. If the underlying problem is that the disk is simply too full, work through startup disk full on Mac and the broader System Data storage guide, since snapshots are counted inside that category.

It is also worth checking whether the space is genuinely purgeable or whether you have accumulated real, deletable files that you simply have not found yet. A visual disk space analyzer answers that question quickly, and duplicates are a common hidden contributor — see removing duplicate files on Mac.

Doing this without Terminal

Everything above is achievable with the built-in tools and a few commands, and if you are comfortable in Terminal there is no reason to add software. If you are not, CleanerMac surfaces the same information as a plain reading of your disk — including what is held by snapshots versus what is genuinely deletable — and clears the reclaimable parts without you needing to remember tmutil syntax. Everything runs locally, and deletions of your own files go to the Trash.

Things not to do

• Do not disable Time Machine snapshots system-wide just to avoid purgeable space. Local snapshots have saved a great many people from accidental deletions.
• Do not delete snapshot files directly from the filesystem. Use tmutil; the snapshot metadata is managed by the filesystem and manual interference can leave the volume in an inconsistent state.
• Do not repeatedly fill the disk to force a purge. It works, but it is unnecessary wear and there is a one-line command that does the same thing cleanly.
• Do not panic at a large purgeable figure right after a big deletion. Give macOS an hour, or thin the snapshots deliberately.

Turn purgeable space into real free space

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