Reference

Purgeable space

Purgeable space is storage that macOS can reclaim automatically when the disk fills up — mainly caches, regenerable files, and cloud-stored content that has already been uploaded. It still appears used, but macOS frees it on demand rather than failing a write.

MacmacOS

Purgeable space

Also known as: purgeable storage, purgeable Mac, macOS purgeable

Space macOS can reclaim automatically on demand
Includes caches, snapshots, and iCloud-offloaded originals
No manual purge button; freed when the disk fills

What makes space purgeable

macOS marks certain files as safe to remove if the disk runs out of room: app and system caches, APFS local snapshots, and originals of photos and files stored in iCloud once smaller local copies exist. Because they can be re-downloaded or rebuilt, the system treats them as a reserve.

This is why free space can seem off. A disk may report little free space while holding gigabytes of purgeable storage that macOS will release the moment an app needs it.

How to see and free it

Open Apple menu > System Settings > General > Storage to see how much space is in use. macOS does not expose a separate "purge now" button — it clears purgeable space on its own when the disk gets tight.

To prompt it along, empty the Trash, remove large downloads, and let local snapshots age out. Most purgeable content returns automatically as you keep using the Mac.

Related terms

Keep reading the reference.

MacSystem Data (Mac)System Data on a Mac is the catch-all storage category for caches, logs, temporary files, fonts, virtual memory, and APFS local snapshots that do not fit Apps, Photos, or Documents. Much of it is reclaimable cache that macOS manages and purges on its own as space runs low.macOS MacAPFS local snapshotAn APFS local snapshot is a point-in-time copy of your startup disk that Time Machine stores locally so you can restore recent changes even without the backup drive attached. The snapshots temporarily occupy disk space and macOS deletes them automatically when space is needed.macOS Storage conceptsStorage optimizationStorage optimization is a feature that keeps full-resolution originals in the cloud while storing smaller, space-saving copies or previews on the device. You see and use your files normally, and the originals download on demand — so the device holds far less than the full library.General Cloud & backupiCloudiCloud is Apple’s cloud service for storing photos, files, backups, and app data across your devices. Every Apple ID gets 5 GB free; paid iCloud+ tiers add more. iCloud storage is separate from the physical storage on your iPhone.iOSiPadOSmacOS

Act on it

Guides and tools for this topic.

How to Clear Disk Space on a Mac