Is purgeable space the same as System Data?

No, though they overlap. Local snapshots and caches are counted in System Data, but iCloud copies of your documents are purgeable too. System Data is a category; purgeable means macOS can take the space back.

Does a lot of purgeable space slow my Mac down?

No. macOS counts it as available and frees it when an app needs room. A disk that is genuinely full, with little purgeable left, is what slows a Mac.

Why did my purgeable space go up after I deleted files?

A local snapshot may still hold the deleted files. The space becomes purgeable rather than free, and Time Machine releases it when the snapshot ages out or the space is needed.

Mac file guides

What is purgeable space on a Mac?

By Vishva Variya · Updated November 2, 2026 · 5 min read

Short answer

Purgeable space is storage macOS can free by itself when it needs room: local Time Machine snapshots, iCloud files that can be downloaded again, and caches that are safe to delete. Storage settings and Disk Utility count it as available. You can’t delete purgeable files by hand; macOS removes them as space is required.

What counts as purgeable?

Local Time Machine snapshots: one about every hour, each kept for 24 hours, plus one of your last successful backup and one taken before each macOS update.
iCloud Drive and iCloud Photos files kept on the Mac while the originals stay in iCloud. With Optimize Mac Storage on, the local copies can go and come back when you open them.
Caches and logs macOS considers safe to delete: temporary database files, interrupted downloads, staged macOS and app updates, and Safari website data.

Purgeable is a property, not a folder. It describes whether macOS can take the space back, not where the files sit.

Why do Finder, Storage settings and Terminal show different free space?

Apple counts snapshot space and other purgeable space as available, so Storage settings and Disk Utility include it in what they show as available. Terminal’s df counts only blocks that are free right now:

df -h /

The gap between df’s Avail column and the available figure in Storage settings is roughly your purgeable space. Neither number is wrong; one is what’s empty now, the other is what macOS can hand you when you ask.

How does macOS free purgeable space?

1An app or update asks for more space than is free.
2Time Machine deletes local snapshots as they age or as space is needed. It keeps them only on disks with plenty of free space to begin with.
3With Optimize Mac Storage on, iCloud Drive keeps recently opened files and stores older ones only in iCloud.
4macOS clears the caches and logs it considers safe to delete.

That happens without a prompt, which is why a large purgeable figure on its own isn’t a problem.

How do I see and remove local snapshots?

tmutil listlocalsnapshots /

Apple’s way to clear them: open System Settings › General › Time Machine, click Options, set Backup Frequency to Manually, wait a few minutes, then set it back. sudo tmutil deletelocalsnapshots followed by a snapshot’s date (YYYY-MM-DD-HHMMSS) removes one from Terminal.

Why can’t I just force macOS to purge it?

There is no Purge button, and Apple says purgeable files can’t be removed by hand. What you can do is clear the parts you control: delete local snapshots as above, and in iCloud Drive Control-click a file or folder and choose Remove Download. The file stays in iCloud and downloads again when you open it.

If space is still short after that, the cause is files that aren’t purgeable at all: your own videos, downloads and installers.

Seeing purgeable space in Peekaboo

Peekaboo’s Disk Usage lists every folder on the disk by size, plus the space macOS frees on its own (iCloud copies, caches and snapshots), so a big purgeable figure stops looking like a mystery. Local Time Machine snapshots can’t go to the Trash, so Peekaboo removes them only after you turn on permanent removal in Settings › Cleanup. For the space that isn’t purgeable, Clean Up gathers the files you put there yourself.

1Open Disk Usage to see what macOS can free on its own.⇧⌘U
2Open Clean Up for the space macOS won’t free for you.⇧⌘K
3Undo any cleanup that went to the Trash.⌥⌘Z

Questions

Is purgeable space the same as System Data?: No, though they overlap. Local snapshots and caches are counted in System Data, but iCloud copies of your documents are purgeable too. System Data is a category; purgeable means macOS can take the space back.
Does a lot of purgeable space slow my Mac down?: No. macOS counts it as available and frees it when an app needs room. A disk that is genuinely full, with little purgeable left, is what slows a Mac.
Why did my purgeable space go up after I deleted files?: A local snapshot may still hold the deleted files. The space becomes purgeable rather than free, and Time Machine releases it when the snapshot ages out or the space is needed.