How to Clear System Data on a Mac (and Why It Gets So Big)

You open System Settings → General → Storage, wait for the bar to finish calculating, and there it is: a grey slab called System Data taking 60, 100, sometimes 150GB. There's no button to clear it and no list of what's inside. That's because System Data isn't really a category. It's what's left over after macOS has counted everything else.

Quick answer: System Data is a catch-all for caches, logs, Time Machine local snapshots, iPhone and iPad backups, temporary files, developer data and app files macOS can't categorise. You can't clear it in one go, but you can shrink it: restart your Mac, delete old device backups (Finder → your device → Manage Backups), remove Time Machine local snapshots (tmutil in Terminal), clear app caches in ~/Library/Caches, and remove developer data such as Xcode's DerivedData. Don't delete anything in /System or /private/var. MacCove Space breaks System Data into named categories and grades each item Safe, Review or Caution, so you're not guessing what's inside.

What System Data actually is

Until macOS Big Sur this bar was called Other. Since Monterey, macOS shows a separate macOS category for the operating system itself (including Apple Intelligence models), and System Data for everything it can't place elsewhere.

The important thing to understand is that System Data is calculated by subtraction. macOS adds up Applications, Documents, Photos, Mail, Messages and the rest, and whatever space remains in use is labelled System Data. Howard Oakley of The Eclectic Light Company, who has written more about Mac storage than almost anyone, describes it as only "a rough estimate." That's why it can swing by tens of gigabytes between one look and the next.

What's usually inside it

Step 1: Restart, then look again

It sounds too simple, but restarting clears temporary files and swap, and gives macOS a chance to tidy up. System Data often looks much smaller after a restart, especially if your Mac has been running for weeks or has just installed a big update. After a major macOS upgrade, System Data commonly stays inflated for a day or two before settling.

Step 2: Delete old iPhone and iPad backups

If you've ever backed up an iPhone or iPad to your Mac, those backups count as System Data, and each one can be tens of gigabytes. They're easy to forget, especially for devices you no longer own.

1. Connect any device (or skip this if none are around) and open Finder.

2. Select a device in the sidebar, then General → Manage Backups.

3. Right-click an old backup and choose Delete.

Apple warns against moving or editing backup files by hand, so use Finder rather than deleting folders in ~/Library/Application Support/MobileSync directly. Old iPhone software update files (.ipsw) can also sit in ~/Library/iTunes and take several gigabytes each.

Step 3: Remove Time Machine local snapshots

If you use Time Machine, your Mac keeps local snapshots, roughly one an hour for the last 24 hours, plus one before each macOS update. Apple counts this space as available, and macOS deletes snapshots automatically when it needs room, but Storage settings may still lump them into System Data.

To see them, open Terminal and run:

To delete a specific one, copy its date and run:

```sudo tmutil deletelocalsnapshots 2026-10-01-101500```

Or, without Terminal, open **System Settings → General → Time Machine**, turn off automatic backups, wait a few minutes, and turn them back on. Apple suggests this as the way to clear local snapshots.

## Step 4: Clear app caches

Caches are often the biggest single chunk you can safely remove. Quit your apps, press **⇧⌘G** in Finder, go to **~/Library/Caches**, and delete the **contents** of folders belonging to large apps, rather than the folders themselves. Browsers, Spotify, Slack, Teams and creative apps are the usual heavyweights.

Expect caches to grow back, because that's their job. Clearing them makes sense when they've become huge or belong to apps you no longer use. Our guide on how to clear cache on a Mac covers which ones are worth clearing.

## Step 5: Developer data (if you've ever opened Xcode or Docker)

If you develop software, or once installed Xcode to try something, this is often where the biggest System Data hides:

- **Xcode DerivedData** (~/Library/Developer/Xcode/DerivedData): build products that are rebuilt on demand. Safe to delete.
- **Simulator runtimes and devices:** remove old ones in **Xcode → Settings → Components**, and clear unavailable simulators with **xcrun simctl delete unavailable**.
- **iOS device support files:** downloaded every time you connect a device running a new iOS version. Old ones can go.
- **Docker Desktop's disk image:** grows to whatever size you allowed. Clean up with **docker system prune** or reduce the disk limit in Docker Desktop's settings.

## Step 6: Find what's left

If System Data is still huge, find out where the space actually is. In Terminal, this read-only command lists the size of each folder in your Library, smallest to largest:

```du -sh ~/Library/* 2>/dev/null | sort -h```

Repeat it inside whichever folder is biggest (for example **~/Library/Application Support/\***) until you find the culprit. Terminal may need **Full Disk Access** (System Settings → Privacy & Security) to see protected folders.

This is the slow part, and it's exactly why System Data is so frustrating: the space is spread across dozens of folders with names like com.developer.helper, and you have to work out what each one belongs to. MacCove Space does this mapping for you. It scans the whole disk, breaks System Data into named categories (caches, logs, developer data, AI tool data, leftovers from deleted apps), and grades each item Safe, Review or Caution, so you only clear what's genuinely disposable.

## Purgeable space: why the numbers don't match

You may notice that Finder, Disk Utility and Storage settings all report different amounts of free space. Part of the reason is **purgeable** space: snapshots, caches and iCloud files that macOS *could* delete if it needed the room. Finder counts that as available; Disk Utility shows it separately in brackets. Don't count on macOS freeing purgeable space before you run out, though. If you're trying to install an update or copy a big file, clearing the items above is more reliable.

## What not to delete

- Anything in **/System**. It's protected anyway, and you don't want to fight it.
- **/private/var/vm** (swap and sleep image). Restart instead.
- The **Spotlight index**, unless search is actually broken.
- **Group Containers** for apps you still use; they're shared between apps from the same developer.
- iPhone backups you don't have another copy of.

## FAQs

### Why is System Data so large on my Mac?

Usually a mix of Time Machine local snapshots, caches, old iPhone backups and developer data, plus leftovers from apps you've deleted. Reports of 100GB or more are common, and it hurts most on 256GB Macs.

### Can I delete System Data?

Not as a single thing, because it's a label for many different files. You can delete most of what's inside it, as long as you remove the right pieces and leave macOS's own files alone.

### Does Safe Mode clear System Data?

It helps a little. Apple says starting up in Safe Mode clears certain system caches, which can free enough room to install an update. Don't expect it to reclaim tens of gigabytes.

### Why did System Data grow after a macOS update?

Updates leave snapshots, downloaded installers and rebuilt caches behind, and Spotlight re-indexes the disk. Most of this settles within a day or two. If it doesn't, work through the steps above.

### Will reinstalling macOS reduce System Data?

Rarely by much, because most System Data lives in your user Library, which a reinstall keeps. Clean up the contributors above instead.

## Related guides

- How to Free Up Disk Space on a Mac
- How to Clear Cache on a Mac
- How to Uninstall Apps on a Mac Completely
- [Why Managing Storage on a Mac Is So Painful](dato:item/GvPZrCqVQBingeZOvZUOdg)

## Sources

- [Apple: Free up storage space on Mac](https://support.apple.com/en-us/102624)
- [Apple: About Time Machine local snapshots](https://support.apple.com/en-us/102154)
- [Apple: Delete iPhone or iPad backups on Mac](https://support.apple.com/en-us/108809)
- [Apple: How much storage Apple Intelligence uses](https://support.apple.com/en-us/121115)
- [The Eclectic Light Company: What is System Data in Storage settings?](https://eclecticlight.co/2025/02/11/what-is-system-data-in-storage-settings/)
- [The Eclectic Light Company: Explainer: Storage settings](https://eclecticlight.co/2025/12/20/explainer-storage-settings/)
- [Macworld: How to delete System Data on Mac](https://www.macworld.com/article/676493/how-to-delete-system-data-mac.html)