Your disk is full — except it isn't: making sense of purgeable space on Mac
Your Mac says the disk is almost full. You check Storage in System Settings and the bar is nearly solid. But then you notice a lighter stripe labeled "purgeable" — and somehow it's 20, 40, even 60 GB. That space exists on your disk, macOS knows it's there, yet it still warns you you're running low. What's going on?
What purgeable space actually is
Purgeable space is data that macOS has marked as "safe to delete automatically when disk space runs low." The system keeps it around because it's useful, but promises itself it'll let go when you truly need the room. Think of it as a polite reservation that the system can cancel at any time.
The most common things macOS marks as purgeable:
- Time Machine local snapshots — copies of recent backups stored on your startup disk so you can restore files even when your backup drive isn't connected
- iCloud-optimized files — when "Optimize Mac Storage" is on, macOS keeps full-size copies of your iCloud files locally but marks them purgeable. If space gets tight, it evicts them to iCloud-only stubs
- System and app caches — some internal caches that macOS manages on its own
- Recently deleted Trash items — files in Trash that haven't been permanently removed yet
- Media caches — streamed content, offline Apple TV+ episodes, downloaded podcasts
Why the storage bar looks full even when it's not
Here's the confusing part: different macOS tools report purgeable space differently.
- System Settings > General > Storage counts purgeable space as "used." So the bar looks full even though 30 GB of that could be reclaimed automatically.
- Disk Utility sometimes shows purgeable as available, sometimes as used — depending on how you read the numbers.
- Finder's "Get Info" on your startup disk shows "Available" which usually includes purgeable space, making it look like you have more room than the storage bar suggests.
So you get contradictory numbers from three Apple tools on the same Mac. This isn't a bug exactly — it's a design choice that confuses almost everyone. If your storage numbers feel like they don't add up, you're not alone. We cover more reasons in our guide to Mac storage not adding up.
How to reclaim purgeable space when you need it
In theory, macOS handles this automatically. In practice, it doesn't always reclaim space fast enough — especially when you're trying to download a large file or install an update and need room right now.
1. Empty the Trash
The simplest step. Right-click the Trash icon in the Dock and choose "Empty Trash." Files sitting there count as purgeable until they're actually gone.
2. Remove Time Machine local snapshots
These are often the single largest purgeable chunk. Open Terminal and list them:
tmutil listlocalsnapshots /
To thin them down to the last four hours:
tmutil thinlocalsnapshots / 14400
The number is seconds — 14400 equals four hours. This tells macOS to delete any local snapshot older than that.
3. Turn off iCloud "Optimize Mac Storage" temporarily
Go to System Settings > Apple ID > iCloud > iCloud Drive and uncheck "Optimize Mac Storage." This forces macOS to treat your iCloud files as regular local files, removing the purgeable flag. The files stay on disk, but macOS stops counting them as reclaimable — so it's more likely to free up other purgeable data to compensate.
You can turn optimization back on afterward. macOS will re-optimize over time.
4. Use the built-in storage manager
Open System Settings > General > Storage and click the info button (i) next to categories like Documents, Music, or iOS Files. This built-in tool lets you review and delete large files, old downloads, and device backups that may be purgeable.
5. Restart your Mac
A restart can force macOS to reconcile its purgeable accounting. Some caches and swap files are only released on reboot. It's surprisingly effective when the storage bar looks stuck.
When to leave purgeable space alone
If your Mac isn't complaining about low disk space and you're not trying to install something large, purgeable space is working as designed. It's a performance feature: those Time Machine snapshots protect you, iCloud caches speed up file access, and macOS knows when to let go.
Chasing purgeable space to zero means removing useful data that macOS was managing intelligently. The system will reclaim what it needs when it actually needs it. Worry about purgeable space only when you're genuinely blocked — for example, when your startup disk is full and macOS hasn't caught up yet.
Quick check: Open Terminal and run df -h / — the "Avail" column shows space that's actually free right now, not counting purgeable. If that number is above 15–20 GB, you're fine. Below 10 GB is when things start slowing down.
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Meet Gigatidy →FAQ
Does purgeable space count as free space on Mac?
It depends on which tool you ask. Finder's "Get Info" usually includes purgeable in available space, but System Settings counts it as used. In practice, macOS can reclaim purgeable space automatically when needed, so it's somewhere between "used" and "free."
How do I force my Mac to free purgeable space?
Empty the Trash, thin Time Machine local snapshots with the tmutil command, and restart your Mac. If iCloud's "Optimize Mac Storage" is on, temporarily disabling it can also help macOS recalculate. In most cases, a restart alone shakes loose several gigabytes.
Is it safe to delete Time Machine local snapshots?
Yes, as long as you have a recent backup on your actual Time Machine drive. Local snapshots are a convenience copy — they let you restore recent files without connecting your backup drive. If your backup drive has everything, deleting local snapshots is safe and often frees the most space.