TidyMacPurgeable space is storage macOS promises to free when needed, mostly Time Machine local snapshots and iCloud-cached files. Finder counts it as available, but the release can lag, so installers fail with “not enough space”. Thinning local snapshots and restarting turns purgeable space into real free space.
- Compare “available” in Finder with real free space from Terminal (df -h /).
- List local snapshots with tmutil listlocalsnapshots /.
- Thin them with sudo tmutil thinlocalsnapshots / 999999999999 4.
- Restart, then check free space again.
Two different numbers
Finder and System Settings show available space, which includes purgeable space. Terminal shows what's truly free right now:
df -h /If Finder says 60 GB available and df says 8 GB free, about 52 GB is purgeable.
What counts as purgeable
- Time Machine local snapshots, the main one. What they are
- Files in iCloud Drive that are also stored locally and can be removed from this Mac.
- Some system caches macOS can rebuild.
Let TidyMac do this for you
Scan free, see every part of your storage explained, and clean only what’s safe. Everything goes to the Trash first.
Make it real
tmutil listlocalsnapshots /
sudo tmutil thinlocalsnapshots / 999999999999 4Then restart. Run df -h / again and the free number should be close to what Finder showed.
Why TidyMac always says "about"
The size of purgeable space is an estimate macOS gives; nobody can measure it exactly until it's released. TidyMac shows snapshots as "about 24 GB" and re-measures after cleaning, so the number you see afterwards is real.