What is purgeable space on a Mac, and how do you free it?

Purgeable space is storage that macOS has agreed to give back whenever something needs it, but hasn't given back yet. Finder counts it as free. Terminal, many installers and some apps don't, which is why a Mac can show 200 GB available and still refuse to install a 30 GB game.

Published October 21, 2026 · Tested on macOS 27 · 7 min read

The short version

Purgeable space is mostly local Time Machine snapshots, plus iCloud files and caches that macOS can delete and fetch or rebuild later.
It is not wasted space. macOS frees it on its own when a write actually needs the room.
You only need to free it by hand when an app checks free space before it starts and gives up.
The quickest fix is sudo tmutil deletelocalsnapshots /. It removes your local snapshots and doesn't touch the backups on your Time Machine disk.

How to see how much purgeable space you have

macOS shows two different numbers for free space, and purgeable space is the gap between them.

Finder. Select your startup disk (usually Macintosh HD), then choose File › Get Info. The Available line includes purgeable space and shows it in brackets, for example "Available: 212 GB (45.4 GB purgeable)".
Terminal. Run df -h /. The Avail column is space that is free right now, without purgeable data. diskutil info / calls the same figure Container Free Space.

$ df -h /
Filesystem      Size   Used  Avail Capacity  Mounted on
/dev/disk3s3s1  460Gi   13Gi  158Gi     8%   /

Subtract the Terminal figure from Finder's figure and you have roughly the purgeable amount. If you write software, the two volume keys behind these numbers are volumeAvailableCapacityForImportantUsage (which includes purgeable data) and volumeAvailableCapacity (which doesn't). CleanMacster estimates purgeable space from the difference between them.

What is inside purgeable space

Purgeable data is anything macOS can delete without losing something you can't get back. On most Macs it comes from four places:

Local Time Machine snapshots. With automatic backups turned on, Time Machine saves a snapshot of your startup disk about every hour and keeps each one for 24 hours. It also keeps a snapshot of your last successful backup until the space is needed, and takes one before every macOS update. A snapshot holds on to files you have since deleted or changed, so it can grow large after you clear out a big folder.
iCloud Drive files. With Optimize Mac Storage turned on, files you have downloaded from iCloud Drive can be removed from the Mac again, because a copy stays in iCloud.
Photos originals. With Optimize Mac Storage turned on in Photos, full-size originals can be swapped back to smaller versions while the originals stay in iCloud.
Caches Apple apps mark as removable. For example, the App Store keeps a manifest of download caches it lists as purgeable, and streaming apps keep caches they can download again.

What a real Mac looked like

On the Mac we test CleanMacster on, Finder reported 45.4 GB of purgeable space in October 2026. We asked macOS to release it. It freed 44.5 GB in 35 seconds and left 1.0 GB. All 23 local Time Machine snapshots were gone afterwards, so on that Mac nearly all of the purgeable space was snapshots. That matches what most people find: if purgeable space is large, check snapshots first.

Why macOS doesn't just free it

macOS releases purgeable space when an app actually writes data and the disk runs short. It doesn't release it because an app asked how much space is free. An installer or game launcher that checks free space first sees the smaller number, decides there isn't enough room and stops before anything is written, so macOS is never asked to make room.

That is why the problem shows up with installers, large game downloads, virtual machine tools, video exports and scripts that call df, while copying files in Finder usually works.

How to free purgeable space now

1. Thin or delete local Time Machine snapshots

Open Terminal and list the snapshots on your startup disk:

$ tmutil listlocalsnapshots /
Snapshots for disk /:
com.apple.TimeMachine.2026-10-21-121254.local
com.apple.TimeMachine.2026-10-21-132253.local
com.apple.TimeMachine.2026-10-21-142253.local

To let macOS pick which snapshots to drop until it has freed a given amount, thin them. The amount is in bytes, and 4 is the highest urgency:

sudo tmutil thinlocalsnapshots / 20000000000 4

To remove every local snapshot on the startup disk at once:

sudo tmutil deletelocalsnapshots /

To remove a single snapshot, pass its date instead of the disk, for example sudo tmutil deletelocalsnapshots 2026-10-21-121254. Terminal asks for your administrator password.

What you lose: the hourly restore points from the last day that are stored on the Mac itself. Backups on your Time Machine disk or network drive are not affected, and Time Machine starts taking new local snapshots again within the hour.

2. Remove downloaded iCloud Drive files

In Finder, Control-click a large folder in iCloud Drive and choose Remove Download. The files stay in iCloud and download again when you open them.

3. Use CleanMacster

In CleanMacster, the Performance module lists Free Up Purgeable Space under maintenance tasks whenever there is enough to be worth it, with an estimate of how much it can release. The task asks the macOS service that normally frees space under pressure to do it now, so macOS decides what goes. The task's description says that this includes local Time Machine snapshots. A separate, unselected task, Thin Time Machine Snapshots, removes only the snapshots macOS can spare, up to 1 GB. Neither task needs your password.

What not to do

An old tip is to fill the disk with a huge file (with mkfile or dd) so that macOS panics and purges. It works, but if the disk fills up completely, apps can crash, unsaved work can be lost and macOS can struggle to boot. The methods above free the same space without that risk.

Common questions

Is it safe to delete purgeable space?

Yes. Everything in it is either stored somewhere else (iCloud, your backup disk) or can be rebuilt. The only thing you give up is the local snapshots, which you would only miss if you needed to restore a file from the last 24 hours while your backup disk was not connected.

Why does purgeable space come back?

Because the things that create it keep running. Time Machine takes a new local snapshot every hour, iCloud downloads files as you open them and apps refill their caches. A few gigabytes reappearing within a day is normal.

Can I stop local snapshots altogether?

Only by turning off Back Up Automatically in Time Machine settings, which also stops your regular backups. That is a bad trade for a few gigabytes. Freeing the space when you need it is better.

Is purgeable space the same as System Data?

No, but they overlap. Space held by local snapshots often shows up inside System Data in Storage settings, which is one reason System Data can look alarming. See why System Data is so big.