What purgeable space on a Mac actually is
Purgeable space is storage that holds files macOS considers optional. They are still on your disk, but macOS has decided it can delete them the moment something needs the room. Because of that promise, macOS adds purgeable space to the available figure it shows you.
That is why two numbers can disagree. Storage settings may say 80 GB is available, while an installer that checks free space sees only 30 GB. The missing 50 GB is purgeable.
What fills purgeable space
| Source | What it is | How it goes away |
|---|---|---|
| Time Machine local snapshots | Hourly copies of your disk, kept for about 24 hours | Delete in Disk Utility or with tmutil |
| Optimised iCloud Drive files | Local copies of files that also live in iCloud | macOS removes them, or you click Remove Download |
| Optimised Photos originals | Full-size photos stored in iCloud Photos | macOS swaps them for smaller versions |
| System caches | Files macOS can rebuild on demand | Cleared by macOS, or by a restart |
| Watched Apple TV content | Films and shows you have already watched | Delete in the TV app |
Apple says Time Machine saves a local snapshot of your startup disk about every hour and keeps it for 24 hours. It also keeps the snapshot of your last successful backup until space is needed. If you deleted a large folder this morning, a snapshot may still hold a copy, so the space doesn’t come back yet.
How to check purgeable space on your Mac
Newer versions of Storage settings fold purgeable space into the available figure, so use Finder instead.
- Open a Finder window. If your disk isn’t in the sidebar, choose Finder, then Settings, then Sidebar, and tick Hard disks.
- Click Macintosh HD in the sidebar and press Command-I.
- Read the Available line. The purgeable amount appears in brackets after it, for example 120 GB (42 GB purgeable).
Check it in Disk Utility
Open Disk Utility from /Applications/Utilities and select your startup volume. On most macOS versions it shows Free space separately from what Finder calls available. The difference between the two is roughly your purgeable space.
5 ways to clear purgeable space on a Mac
Start at the top. The first method frees the most space on most Macs.
1. Delete Time Machine snapshots in Disk Utility
On macOS Monterey and later, you can see and delete snapshots without Terminal.
- Open Disk Utility and select your startup volume, usually Macintosh HD or Macintosh HD - Data.
- Choose View, then Show APFS Snapshots. A list appears at the bottom of the window.
- Select the snapshots whose names start with
com.apple.TimeMachine, click the minus button and confirm.
Leave snapshots named com.apple.os.update alone. macOS uses those during and after updates.
2. Delete snapshots with Terminal
If you prefer the command line, Terminal gives you the same result.
- List your snapshots:
tmutil listlocalsnapshots / - Delete one by its date:
sudo tmutil deletelocalsnapshots 2026-11-13-091500 - Enter your Mac password when asked. Nothing appears as you type, which is normal.
Replace the date with one from your own list. To ask macOS to thin snapshots as hard as it can in one go, run tmutil thinlocalsnapshots / 999999999999 4. Run man tmutil to read the options on your version.
The no-Terminal shortcut
Apple’s own advice is simpler. Open System Settings, then General, then Time Machine, turn off automatic backups, wait a few minutes and turn them back on. macOS removes the local snapshots in between.
3. Remove local copies of iCloud Drive files
With Optimise Mac Storage on, iCloud Drive files you haven’t opened in a while count as purgeable. To free them now, right-click a large folder in iCloud Drive and choose Remove Download. The files stay in iCloud and download again when you open them.
Don’t press Delete on those files. Deleting removes them from iCloud and every other device signed in to your Apple Account.
4. Restart your Mac
A restart clears temporary files and some system caches. It won’t touch snapshots or iCloud files, so treat it as a small win. Note the purgeable figure before and after so you know what it did.
5. Clear caches you control
App and browser caches don’t always count as purgeable, but clearing them gives macOS free space straight away. Our guide on how to clear cache on a Mac shows which folders are safe to empty.
Methods to skip
Filling the disk with a huge file
An old trick is to create a giant file until macOS panics and purges, then delete it. On APFS this is unreliable, and running a disk to zero free space can crash apps and corrupt files mid-save. It isn’t worth the risk.
Running sudo purge
Despite the name, sudo purge flushes memory caches in RAM. It doesn’t free a single byte of purgeable disk space.
Apps that promise one-click purging
Some apps claim to clear purgeable space in one click. Under the hood, they ask macOS to thin snapshots, which you can do yourself for free with the methods above.
When to leave purgeable space alone
Purgeable space isn’t wasted. Snapshots let you recover a file you deleted by mistake an hour ago, and local iCloud copies open instantly. macOS frees this space by itself when Finder copies files, when you download large items and when most apps save.
Clear it by hand only when one of these happens:
- A macOS update says there isn’t enough space, even though Storage settings shows plenty.
- An app such as a video editor or a virtual machine tool refuses to start because the disk looks full.
- You deleted a lot of data and need the space back today, not tomorrow.
If your update is the problem, our guide on what to do when there isn’t enough space to update your Mac covers the full fix.
Why purgeable space grows after you delete files
It feels backwards. You delete 30 GB of old videos, and available space barely moves while purgeable space jumps. The reason is the most recent Time Machine snapshot. It still points to those videos, so APFS keeps the blocks on disk until the snapshot expires.
Wait a day and the snapshot ages out on its own, or delete it with method 1 or 2 above and get the space back now. Either way, nothing is wrong with your disk. If you back up to an external Time Machine drive, the videos are still in that backup after the local snapshot goes.
How long until macOS clears it by itself
Hourly snapshots normally expire after 24 hours. Optimised iCloud files and caches have no fixed timer. macOS removes them when free space runs low or when an app asks for room. That is why the purgeable figure can look stuck for weeks on a Mac with plenty of free space, and vanish within minutes on a nearly full one.
Purgeable space vs System Data
They overlap but aren’t the same. System Data is a category in Storage settings that groups caches, logs, snapshots, virtual memory and other files macOS can’t put elsewhere. Some of it is purgeable, and much of it isn’t. If the grey System Data bar is your problem, read how to reduce System Data on a Mac.
If you also back up an iPhone to this Mac, check those backups next. They are rarely purgeable, and they are often the biggest single item on the disk. Our guide on how to delete iPhone backups on a Mac walks through it.
Make space that stays free with MyMacStorage
Purgeable space comes and goes on its own. Real free space comes from removing files you don’t need. MyMacStorage scans your Mac on the device, shows exactly what takes up room and clears it to the Trash. It costs $14.99 once, with no subscription. Learn more on the home page.