# Purgeable space on a Mac: what it is and why Finder and df disagree

> Purgeable space is data macOS can delete on its own when it needs room. Learn what counts, why Finder and df disagree, and when to free it yourself.

- URL: https://moreroom.app/learn/purgeable-space-mac
- Published: 2026-10-17
- Updated: 2026-10-17
- Publisher: MoreRoom (Yando Pte. Ltd.) — https://moreroom.app

## TL;DR

- Purgeable space is storage used by data that macOS considers disposable and will remove by itself when it needs room.
- It typically includes local Time Machine snapshots, some caches, and local copies of iCloud files that can be downloaded again.
- Finder and Storage settings count purgeable space as available; Terminal’s df and Disk Utility’s Free figure do not.
- macOS frees purgeable space automatically when an app or update needs it, so you rarely need to force it.
- If a tool insists on real free space, restart first, then thin local snapshots with tmutil.

**Purgeable space is storage that is in use right now but that macOS treats as disposable and will free by itself when it needs room.** It typically includes local Time Machine snapshots, some caches, and local copies of iCloud files that can be downloaded again. Finder and Storage settings count it as available space; Terminal’s `df` and Disk Utility’s Free figure do not. In everyday use you do not need to do anything about it.

## What counts as purgeable?

Apple does not publish a complete list, and the mix changes with macOS versions and with what you have turned on. In practice, purgeable space is made up of data that a system service has registered as safe to remove. A background process called `deleted` keeps track of it, listens for low-space warnings and asks each service to give space back. You can read its short description with `man deleted`.

Typical contents:

- **Local Time Machine snapshots.** Apple says your Mac counts the space used by snapshots as available storage, and removes them as they age or when space is needed ([About Time Machine local snapshots](https://support.apple.com/en-us/102154)).
- **Caches and temporary data that macOS manages.** Apple’s [optimise storage guide](https://support.apple.com/guide/mac-help/sysp4ee93ca4/mac) says macOS clears caches and logs that are safe to delete when space is needed, giving examples such as temporary database files, interrupted downloads, staged macOS and app updates and Safari website data.
- **Local copies of cloud files.** With Optimize Mac Storage on for iCloud Drive, files already uploaded can be removed locally and downloaded again when opened. Depending on the version and settings, some of this space is reported as purgeable.
- **Media you can download again.** With **Optimize Storage** on, Apple TV movies and shows you have watched can be removed automatically.

Not everything that looks disposable is purgeable. Your own caches in `~/Library/Caches`, old downloads and iPhone backups are ordinary used space until you delete them.

## Why Finder and df disagree

Each tool answers a slightly different question.

![Finder’s Available figure includes purgeable space; df shows only free space](https://moreroom.app/learn/img/purgeable-space-mac-finder-vs-df.svg)

| Where you look | What it shows | Includes purgeable? |
|---|---|---|
| Finder › File › Get Info on the startup disk | Available, with purgeable in brackets | Yes |
| Finder status bar (View › Show Status Bar) | Available | Yes |
| System Settings › General › Storage | Available | Generally yes |
| Terminal: `df -h /` | `Avail` | No |
| Terminal: `diskutil info /` | Container Free Space | No |
| Disk Utility | Free in the usage bar; Available, with purgeable in brackets, in the details | Free: no; Available: yes |

In Apple’s developer terms, Finder reports the capacity available for “important” usage, which includes space the system can purge, while `df` reads the file system’s free block count. Neither is wrong. The gap between them is roughly the purgeable amount. It is normal for it to range from a few gigabytes to tens of gigabytes, depending on snapshots and caches.

A side effect: when you delete a file that a local snapshot still holds, Finder’s Available may rise while `df` stays the same. Our guide to [deleted files that don’t free space](https://moreroom.app/learn/deleted-files-storage-not-changing) covers that case.

## When does macOS free it?

macOS frees purgeable space on demand, not on a schedule you can see:

- When an app or installer asks the system for space it needs, macOS purges enough to make room. Apple says local snapshots do not take up space needed for downloads, copying files or installing software.
- When free space runs low, the `deleted` process asks services to give space back.
- Local Time Machine snapshots are removed after 24 hours anyway.

There can be a delay, and the purgeable figure Finder shows is an estimate rather than a promise. Apps that check raw free space instead of asking macOS do not trigger purging.

## Should you force it?

Usually not. If you want to install an update or copy files and Finder says there is enough space, try it: the system frees what it needs. Forcing it removes restore points and caches that make your Mac faster or safer, for no lasting gain.

It can help when a tool checks raw free space and refuses to start, for example some command-line installers, virtual machine tools or apps that create large disk images. Try these in order:

1. **Retry the task once.** It may have triggered purging already.
2. **Restart the Mac.** This releases swap and temporary files.
3. **Thin local snapshots.** This asks Time Machine to remove snapshots until it reclaims the amount you ask for:

```sh
tmutil thinlocalsnapshots / 20000000000 4
```

The first number is the target in bytes (here 20 GB, decimal) and the last is the urgency, from 1 to 4. The command removes only Time Machine’s own local snapshots, and removed snapshots cannot be restored. Your Time Machine backups on the backup disk are not affected. See [Time Machine local snapshots](https://moreroom.app/learn/time-machine-local-snapshots) for the trade-offs.

4. **Free local copies of cloud files** with **Remove Download** in Finder ([Apple Support](https://support.apple.com/guide/mac-help/mchl1a02d711/mac)). The files stay in iCloud and download again when opened. Our guide to [Remove Download versus delete](https://moreroom.app/learn/icloud-remove-download-vs-delete) explains the difference.
5. **Start up in safe mode once.** Apple notes this clears some system caches ([Free up storage space on Mac](https://support.apple.com/en-us/102624)). Restart normally afterwards.

Avoid tricks that fill the disk with a huge temporary file to make macOS panic and purge. Running a startup disk completely full can make apps fail to save and can leave the system unstable.

## Purgeable space and System Data

The two figures overlap but are not the same. [System Data](https://moreroom.app/learn/what-is-system-data-mac) is a label for whatever Storage settings cannot classify, while purgeable is a property of data that macOS can remove. Local snapshots and system caches are often both. That is why System Data can shrink by itself a day after you delete large files. See the glossary entries for [purgeable space](https://moreroom.app/glossary#purgeable-space) and [local snapshots](https://moreroom.app/glossary#local-snapshot) for short definitions.

## How MoreRoom helps

MoreRoom’s free version shows what macOS will purge on its own, separately from what it will not, as part of **System Data, explained**. It explains why Finder and `df` disagree on your Mac, lists local snapshots, and its Storage Weather view tracks free space over 30 days with a forecast of when the disk fills up. Keep in the Cloud removes local downloads of files already in iCloud Drive, Dropbox, OneDrive or Google Drive, one folder at a time, like Finder’s Remove Download; Pro does whole cloud drives in one go. MoreRoom does not delete snapshots or force purging; use `tmutil` for that.

## FAQ

### What does purgeable mean on a Mac?

It is space used by data macOS can delete without asking you, such as local Time Machine snapshots and some caches. macOS removes it automatically when space is needed.

### Can I delete purgeable space manually?

Not directly, because it is not a folder. You can remove some of what makes it up, for example by thinning local snapshots with tmutil or using Remove Download on iCloud Drive files.

### Why does Finder show more free space than df?

Finder’s Available figure adds purgeable space to free space, because macOS can reclaim it on demand. df shows only blocks that are free right now.

### Is purgeable space part of System Data?

It can overlap. Local snapshots and caches are both purgeable and among the things Storage settings tends to place in System Data, so the two figures are related but not the same.

### Why won’t my Mac free its purgeable space?

macOS frees it only when something asks for space, and some tools check raw free space without asking. Restart, retry, and if needed thin local snapshots with tmutil.