Guide

Purgeable space on Mac, and why deleting files frees nothing

You deleted 40 GB, emptied the Trash, and free space barely moved. Nothing is broken. Those bytes became purgeable: space macOS is holding but promises to release when something actually needs it.

What purgeable actually means

On APFS volumes macOS keeps a reserve of data it can throw away at short notice, and counts it as used until it does. Three things make up most of it: Time Machine local snapshots taken on your startup disk, files stored in iCloud whose local copy can be evicted because the original is in the cloud, and caches the system can rebuild. macOS reclaims that space on demand — when an installer needs room, when a large copy is running out of space, or when a snapshot ages out. From your side it looks like free space that refuses to appear.

Why Finder and Terminal disagree

About This Mac and the Finder status bar tend to include purgeable bytes in what they show as available, while df -h in Terminal reports the raw filesystem numbers. That is why the two can differ by tens of gigabytes, and why a "disk almost full" warning can arrive while Finder still claims plenty of room. Neither is lying; they are answering different questions. When the numbers disagree, believe the one that is stopping you from installing an update.

How to get the space back for real

01
Empty the Trash and wait Give macOS a few idle minutes. A lot of purgeable space is released without you doing anything, and waiting is cheaper than deleting something you wanted.
02
Restart the Mac A restart is the most reliable way to drop stale snapshots and caches. Check free space before and after; the difference is often several gigabytes.
03
Check for local snapshots tmutil listlocalsnapshots / shows the snapshots macOS is keeping on the startup disk. They are meant to expire on their own, and the safe fix is to attach the backup drive and let a normal Time Machine run take over.
04
Look at what iCloud is holding locally Optimise Mac Storage keeps local copies of cloud files until space is needed. Those copies are purgeable by design, so a full-looking Desktop and Documents folder may be costing you far less than it appears.
05
Then measure real files Once purgeable space has settled, measure the volume and cut something real. Deleting your own files to chase a number that was about to drop by itself is how good files get lost.

How Sift tells them apart

Sift measures the volume byte by byte and separates real files from the space macOS is holding back — iCloud placeholders and local snapshots — instead of quietly folding one into the other. It also shows what macOS keeps sealed as a single hatched row, so your totals still match Finder. Scanning and browsing are free forever, which means you can see the difference before spending anything.

See real files versus reserved space

Common questions

Why is my purgeable space so large?

Almost always Time Machine local snapshots that piled up while the backup drive was disconnected, or iCloud files kept locally under Optimise Mac Storage. Both are released as space is needed, and both shrink after a restart with the backup drive attached.

Can I remove purgeable space manually?

You should not need to, and the aggressive methods people share online risk your backups. Empty the Trash, restart, and let a Time Machine backup run. macOS is designed to hand the space back when something needs it.

Does purgeable space count as free space?

It depends who is counting. Finder and About This Mac usually include it in available space, df in Terminal does not, and installers make their own judgement. Treat purgeable as space you will probably get, not space you have.