Finding specific things

Purgeable space, explained properly

Updated 2026-08-08 · 5 min read

APFS reports two kinds of free space: truly free, and purgeable — space macOS could reclaim if pressed. The gap between them explains most of the confusing numbers, and one command reclaims the bulk of it.

What macOS considers purgeable

Purgeable space is data macOS is confident it can delete or re-download when the disk runs short:

• Time Machine local snapshots — complete, dated views of the disk kept locally
• Optimised storage — full-resolution photos and iCloud files that exist in the cloud
• Caches the system knows how to rebuild

Finder's free-space figure usually includes purgeable space; Disk Utility separates it. That is the whole disagreement between the numbers.

Why a copy can still fail

Purging is not instant. A large copy can ask for space faster than macOS reclaims it, and some operations check the strict free figure. So a disk showing 60 GB available with 40 GB purgeable can genuinely refuse a 30 GB file.

Reclaim it deliberately

Snapshots are the usual bulk. List and thin them:

tmutil listlocalsnapshots /
tmutil thinlocalsnapshots / 999999999999 4

The second command asks APFS to delete snapshots until the requested bytes are free, with urgency 4. It is the supported way to do what restarting into recovery and waiting overnight do by accident.

For optimised storage, System Settings → Apple ID → iCloud and Photos' own settings control what is kept locally. Downloading originals converts purgeable to used; removing them converts used to purgeable, not to free.

Finding what is actually large

Once purgeable space is accounted for, what remains is real files. Sort the disk by size and the answer is rarely subtle — a forgotten video export, an old VM, a node_modules graveyard. Spotlight cannot sort the whole disk by size, but find can:

find ~ -type f -size +1G -exec ls -lh {} \; 2>/dev/null

An indexed search app does the same in milliseconds with a query like size:>1gb, external drives included.

Common questions

How do I delete purgeable space manually?

You mostly do not. Thin snapshots with tmutil, review optimised storage settings, and let macOS handle the rest. Deleting the underlying folders by hand is unsupported and risky.

Is purgeable space causing my Mac to feel full?

It can. Some apps and installers read the strict free figure, so tens of purgeable gigabytes still trigger low-disk warnings until they are thinned.