Help · Mac storage
What is System Data on a Mac?
System Data is the grey part of the bar in System Settings › General › Storage. It's macOS's label for everything that doesn't fit its other categories, which is why it can look huge and mysterious.
Seeing “Other” instead of System Data?
Older versions of macOS showed this category as Other in About This Mac › Storage. Apple describes System Data and Other as the same thing: a general category for files from macOS and other apps that don't fit a more specific category. Everything on this page applies to it. On macOS Ventura and later, you'll find it in System Settings › General › Storage.
What's usually in it
- Caches and temporary files that apps and macOS keep to run faster. They grow and shrink on their own.
- Logs that record what apps and macOS have been doing.
- Local Time Machine snapshots. If you use Time Machine, macOS keeps recent snapshots on your Mac and deletes them automatically when it needs the space.
- Virtual memory and sleep files macOS uses while your Mac is running.
- Developer files: Xcode build data, simulators and downloaded device support files can add up to tens of gigabytes.
- Virtual machines and containers: disk images from Docker, Parallels, UTM and similar apps.
- App data that apps store out of sight, such as offline libraries and support files.
What you can safely do
- Restart your Mac. It clears temporary files and virtual memory. System Data often drops noticeably afterwards.
- Give it a day after a macOS update. System Data can look large while an update finishes and Spotlight re-indexes, then settle down.
- If you use Xcode: remove simulators you don't need in Xcode › Settings › Platforms (or Components). Build data in
~/Library/Developer/Xcode/DerivedDatais rebuilt when needed, so it can go. - If you use Docker or virtual machines: remove containers, images and virtual machines you no longer use from within those apps. Their disk images can be very large.
- Don't delete snapshots or caches by hand. macOS removes local snapshots itself when space runs low, and caches come back. Deleting the wrong system folder can cause problems.
Why it's hard to see what's inside
macOS shows System Data as a single number. To see the actual folders, you need a tool that scans your whole disk, including the hidden Library folders, and shows sizes folder by folder.
See what's really in System Data.
Pangalin Space Manager's free scan breaks your disk down to the folder and file, and its System Data page accounts for the rest line by line (snapshots, swap, Apple Intelligence models, virtual machines), saying how each figure was measured. You decide what to change; most changes can be undone.
Free to scan · Notarised by Apple · Apple silicon, macOS 13 or later