What is purgeable space on a Mac — and how do you free it?
Finder says you have plenty of space, but an installer says the disk is full. The difference is purgeable space: storage macOS counts as available but hasn't actually freed yet.
What purgeable space is
Purgeable space is data macOS can delete on its own whenever something needs room:
- iCloud Drive files that are safely in iCloud (with Optimize Mac Storage on), which macOS can remove locally and download again when you open them.
- Time Machine local snapshots.
- Some caches, and media you've already watched (with Optimize Storage).
Why the numbers don't agree
Finder's Get Info on your disk and Storage settings include purgeable space in "available". But some apps — and the df command — only count space that's actually free right now. An installer that checks free space may refuse to run even though Finder shows enough.
DiskGarden shows both: Free space (really free now) and Free + purgeable (what macOS can make available).
How to turn it into free space
macOS frees purgeable space when an app asks for it, so most of the time you don't need to do anything. If an app won't start or install because it checks free space directly:
- Restart your Mac; macOS tidies temporary and purgeable data during startup.
- Delete local snapshots you don't need (see the snapshot guide).
- Free real space by removing big files you don't need — here's how to find them.
See where your space went
DiskGarden is a free disk space analyzer for Mac: it maps every folder by size, so the space hogs stand out. No account, and your files never leave your Mac.