Purgeable space on a Mac: what it is and how to clear it

What purgeable space is

Purgeable space is disk space that files are using right now but that macOS can take back whenever it needs to. Apple's Disk Utility guide describes it as space macOS can free by removing files from your computer. It adds that you can't remove files marked purgeable yourself; macOS removes them as space is required.

That makes it both used and available at the same time. An older edition of Apple's System Information guide puts it this way: free space is physically open space on the disk, while available space includes free space plus purgeable caches. So the same gigabytes can count as available in one place and as used in another. That's one of the main reasons Mac storage numbers don't add up.

What's inside purgeable space

Apple doesn't publish a complete list, but its own documentation names the main parts.

• Local Time Machine snapshots. With automatic backups on, Time Machine keeps an hourly snapshot of your startup disk for 24 hours, plus one of your last successful backup until space is needed. Apple's snapshot article says your Mac counts the space they use as available storage. On many Macs this is most of the purgeable figure. See Time Machine local snapshots.
• Caches macOS can rebuild. Apple's storage guide says that when space is needed, macOS clears caches and logs that are safe to delete, including temporary database files, interrupted downloads, staged macOS and app updates, and Safari website data. The Eclectic Light Company adds Quick Look thumbnails and other optional caches, which a macOS service called deleted purges on request.

The storage recommendations work in a similar spirit. With Optimize Storage on, macOS removes Apple TV movies and shows you've watched and keeps only recent Mail attachments when space is needed. With Store in iCloud on, it keeps older files only in iCloud. You can download any of them again.

Purgeable space and System Data

The two overlap. Storage settings counts local snapshots inside System Data, and Apple says the Mac counts the same space as available. So a large System Data figure and a large purgeable figure are often the same gigabytes, seen from two sides. If both are big, check for snapshots first. System Data on a Mac covers the rest of that category.

Why purgeable space doesn't go away

Purgeable space stays until something asks for room. macOS doesn't clear it ahead of time, and that's deliberate: snapshots are your last day of hourly versions, and caches make your Mac faster. When a copy, download or update needs space, macOS asks its caching services how much each can free, then purges in stages until there's enough.

It doesn't always work. In tests published in August 2026, Howard Oakley found that macOS sometimes refused to purge a large snapshot when it should have, and a copy failed for lack of space. Apple Community has many threads with the same complaint: purgeable space that won't purge. When that happens, the fix is almost always to remove local snapshots yourself.

Purgeable space on other volumes

Time Machine makes local snapshots of every APFS volume it backs up, not only the startup disk, as the tmutil manual describes, and Apple says it stores them only on disks with plenty of free space. Snapshots on an external drive use that drive's space, not your startup disk's. If an external APFS drive you back up looks fuller than it should, list its snapshots using its own mount point, for example tmutil listlocalsnapshots /Volumes/Projects, with your drive's name in place of Projects.

How to see purgeable space

Storage settings counts purgeable space as available and doesn't show it as a separate figure. To see it:

• Disk Utility. Choose View > Show All Devices and select your startup volume. The purgeable amount appears with the available space. View > Show APFS Snapshots adds a table of local snapshots with a Private Size and a Cumulative Size column, as Apple's snapshot guide describes.
• Terminal. df reports only space that is truly free, so comparing it with System Settings gives a rough idea of the purgeable part. Use the Data volume, where your files live, and -H for the same decimal units System Settings uses:

df -H /System/Volumes/Data

How to clear purgeable space

You usually don't need to. If an update, copy or app still says there isn't enough room, these steps free the largest part safely, using Apple's own method for local snapshots.

1. 1

   See how much is purgeable

   Open Disk Utility, choose View > Show All Devices, and select your startup volume. Disk Utility shows how much of the used space is purgeable, and the Info button in the toolbar gives the details.

2. 2

   Check for local snapshots

   In Terminal, run tmutil listlocalsnapshots /. Local Time Machine snapshots are usually the largest part of purgeable space.

3. 3

   Pause automatic backups for a few minutes

   Choose Apple menu > System Settings, click General, then Time Machine. Click Options, set Backup Frequency to Manually, click Done, and wait a few minutes while the local snapshots are removed.

4. 4

   Turn automatic backups back on

   Open Options again and set Backup Frequency back to Automatically Every Hour, or what you used before, so your Mac keeps backing up.

5. 5

   Start the task that needs the space

   Begin the copy, download or update. macOS frees purgeable space when something asks for room, so it often succeeds even when free space looked short.

While Backup Frequency is set to Manually, your Mac doesn't back up on its own, so don't forget step 4.

Clearing purgeable space in Terminal

Terminal gives you more control over local snapshots. First, see what's there:

tmutil listlocalsnapshots /

Each line is a snapshot named with its date, like com.apple.TimeMachine.2026-10-20-123456.local. To remove only one, pass its date in the same form. This is permanent too:

tmutil deletelocalsnapshots 2026-10-20-123456

To ask Time Machine to free a set amount by thinning snapshots, give the amount in bytes. This asks for 20 GB:

tmutil thinlocalsnapshots / 20000000000

To remove every local Time Machine snapshot on the startup disk:

tmutil deletelocalsnapshots /

Both commands remove snapshots permanently. They don't go to the Trash, and you can't get them back. Your backups on your Time Machine disk aren't touched. If Terminal says the operation isn't permitted, run the same command with sudo in front and enter your administrator password.

Be careful with tips that fill your disk with a large dummy file to force macOS to purge. If anything goes wrong partway through, you're left with a full startup disk, which is the situation you were trying to avoid.

When a macOS update says there isn't enough space

Updates are the most common moment purgeable space gets in the way. If the installer stops for lack of room, work through the steps above first, since local snapshots are the quickest space to free. If that isn't enough, Apple's free up storage article suggests starting up in safe mode, which clears certain system caches, then installing the update. macOS creates those caches again as needed, so treat it as a one-time step. For lasting room, look at what you can move off the Mac instead: free up space on your Mac covers the options.

Is it safe to delete purgeable space?

Removing local snapshots is safe as long as your Time Machine backups are up to date. What you lose is the last day of hourly versions stored on the Mac itself, which Time Machine uses when your backup disk isn't connected. Time Machine starts making new ones within the hour.

Everything else in purgeable space is meant for macOS to manage. There's nothing to remove by hand. The space is already counted as available, so if System Settings shows enough room, you have it.

How MacClearings shows purgeable space

MacClearings shows purgeable space in two places and never offers it as something to clean up.

The Overview ring gives purgeable space its own slice, apart from what you keep, what you could move to the Trash and what's free. Breakdown explains it in its first line, for example: "49.5 GB of it is purgeable: macOS frees it on its own when space runs low, so System Settings counts it as available." It also lists your local snapshots, how many there are and when the oldest was made, with a "Frees on its own" label. Breakdown reads these with tmutil listlocalsnapshots and doesn't change them.

That's deliberate. Purgeable space is space macOS will give back when it needs it, so counting it as a win would overstate what a cleanup did. When MacClearings moves something you've reviewed to the Trash, that's real space, and it comes back when you empty the Trash. History can undo any cleanup until then.