1. What is Purgeable Space in macOS?
When you open Apple Menu > System Settings > General > Storage, you will often see a gray hashed segment labeled Purgeable. This includes:
- APFS Local Snapshots: Automatic restore points created by Time Machine when disconnected from external backup drives.
- Optimized iCloud Files: Local cached copies of high-resolution photos, documents, and Apple TV video downloads.
- Kernel Font Caches & CoreAnalytics: Temporary compilation artifacts that macOS retains until critical storage thresholds are hit.
2. Why macOS Won't Release Purgeable Files Automatically
Apple designed macOS APFS to only discard purgeable storage when the drive has literally zero bytes left for essential write operations. However, third-party installers (like Xcode, Android Studio, or modern AAA games) check available physical storage before initiating downloads. Because macOS has not released the purgeable space yet, these installers abort with "Not enough free disk space" errors.
3. Forcing macOS to Release Purgeable Space via Terminal
You can trick macOS into triggering its internal cache eviction daemon by creating and immediately deleting a large dummy file:
This creates a 25 GB sequential block, forcing macOS to aggressively evict purgeable caches, and then reclaims both the 25 GB and the evicted purgeable files.
4. Deleting APFS Local Snapshots with tmutil
The single biggest contributor to stubborn purgeable space is unpurged Time Machine local snapshots. Inspect and delete them with these terminal commands:
Instant Purgeable Reclamation in CleanYourMac Space
Instead of running manual terminal loops that require root elevation, CleanYourMac Space provides a visual breakdown of APFS local snapshots and cached cloud replicas with a single safe Purge Cache button.