Purgeable storage on Mac is cached data, local Time Machine snapshots, and iCloud copies that macOS keeps around but considers safe to delete the moment the system urgently needs space. It's the grey block you see in Disk Utility or About This Mac, sometimes tens of gigabytes, with no obvious way to remove it.
TL;DR
- Purgeable storage = reclaimable cache, local snapshots, and offloaded iCloud files macOS will auto-delete under pressure.
- There is no native "Delete Purgeable" button; you nudge macOS into releasing it.
- Local Time Machine snapshots are usually the biggest chunk.
- Restarting, toggling Optimize Mac Storage, and thinning snapshots reclaim the most space.
- It's safe: macOS only purges copies it can recreate or re-download, never your only copy of a file.
What is purgeable storage on Mac?
Purgeable storage is the portion of your disk macOS has filled with data it can throw away on demand. Because the system treats it as free space internally, you never feel it day to day, your Mac just quietly reuses it. The pressure appears the instant you need real, continuous free space: installing a large app, partitioning the drive, or imaging a backup. macOS introduced this behavior alongside the Optimize Mac Storage feature, so a Mac signed into iCloud almost always carries some purgeable space.
What sits inside purgeable storage?
Purgeable space is a mix of recreatable caches and offloaded copies. The usual contents:
| Source | What it is | Why macOS keeps it |
|---|---|---|
| Local Time Machine snapshots | Hourly local backups taken even when no backup drive is attached | Lets you restore recent versions offline |
| iCloud Drive cache | Local copies of files you opened recently | Faster reopening without re-downloading |
| Apple TV / Music downloads | Watched movies and shows, played albums | Convenience caching |
| Language packs, dictionaries, fonts | System assets downloaded on demand | Re-downloadable when needed |
Local snapshots are typically the heaviest item, which is why they're the first thing to target.
How do I force macOS to clear purgeable storage?
There's no native "Delete Purgeable" button, so you push the system to release the space. Try these in order:
- Restart the Mac. A reboot clears several transient caches and recalculates the storage graph.
- Toggle Optimize Mac Storage. Go to
System Settings › Apple ID › iCloud › Optimize Mac Storageand turn it off, then on. This makes the Mac recalculate what is truly local versus offloaded. - Thin local Time Machine snapshots. Open Terminal and run
tmutil listlocalsnapshots /to see them, thentmutil thinlocalsnapshots / 10000000000 4to urgently free roughly 10 GB. Raise the number for more. - Empty the Trash and reboot again so freed space is recalculated.
Step 3 usually accounts for the bulk of purgeable space on a busy Mac.
Is it safe to clear purgeable storage?
Yes. Purgeable storage only contains data macOS can recreate or re-download: local snapshots (your real Time Machine backups on an external drive are untouched), iCloud copies (the originals stay in iCloud), and caches. macOS already deletes this automatically when the disk fills, so manually thinning snapshots simply does sooner what the system would do under pressure. Nothing that exists only on your Mac gets removed. The one caution: thinning local snapshots removes offline restore points, so if you rely on hourly local versions, sync to an external Time Machine drive first.
What if the space won't come back?
If purgeable storage stays stubbornly high after these steps, the weight is often elsewhere, hidden caches, large media files, or app data miscounted by the storage graph. The same recalculation problems show up on phones, where a grey "System Data" or "Other" bar balloons for similar reasons. If you also manage an iPhone, our guide to why System Data is so high on iPhone explains the equivalent cache bloat, and why your storage stays full after deleting photos covers the same delayed-recalculation behavior. For a broader cleanup philosophy, see storage cleanup vs factory reset.
FAQ
Why can't I delete purgeable storage directly on Mac?
macOS doesn't expose a "Delete Purgeable" button because the system manages this space automatically, freeing it only when an operation needs room. You can speed that up by restarting, toggling Optimize Mac Storage, or thinning local Time Machine snapshots in Terminal.
Is purgeable storage really free space?
Purgeable storage is space macOS counts as available because it can delete the contents at any time. It behaves like free space for the system, but it can block operations that need large, continuous free space until macOS actually releases it.
What causes purgeable storage to grow on a Mac?
Purgeable storage grows mainly from local Time Machine snapshots taken automatically, iCloud Drive caches, and downloaded media from Apple TV or Music. Snapshots are usually the largest contributor.
Will thinning Time Machine snapshots delete my real backups?
No. Thinning local snapshots with tmutil only removes the temporary copies stored on your internal drive. Your full Time Machine backups on an external or network drive are completely unaffected.
If your phone shows the same kind of unexplained grey storage, Cleanor scans and clears recoverable clutter locally, with nothing uploaded. See how Cleanor frees up phone storage or get the Cleanor iOS app to reclaim space on the go.