How to clear System Data on a Mac

Updated October 23, 2026

System Data is the grey bar in Storage settings that can grow to a hundred gigabytes or more. It isn't one thing: it's everything macOS can't put in another category.

Where to see it

Open System Settings › General › Storage. The bar at the top shows Applications, Documents, macOS and System Data. macOS doesn't let you open System Data from there, so you have to know what's inside it.

What System Data is usually made of

Caches from apps and macOS, in ~/Library/Caches and /Library/Caches.
Logs and diagnostic reports, in ~/Library/Logs, /Library/Logs and /private/var/log.
Time Machine local snapshots, kept on your disk while your backup drive is away.
iPhone and iPad backups, in ~/Library/Application Support/MobileSync/Backup.
Developer files: Xcode DerivedData, simulators, device support files, package manager caches and Docker disk images.
Swap and sleep image files macOS manages itself. Leave these alone; they shrink on their own after a restart.

Clear it by hand

Restart your Mac. It clears temporary files and swap, and is often worth a few gigabytes.
Check Time Machine snapshots. In Terminal, tmutil listlocalsnapshots / lists them. macOS removes them when it needs space, and connecting your backup drive lets them be copied and cleared.
Delete old device backups. In Finder, select your iPhone in the sidebar, click Manage Backups… and delete the ones you no longer need.
Clear app caches. Quit the apps first, then remove the contents of the app's folder in ~/Library/Caches (not the Caches folder itself). See how to clear cache on a Mac.
Clear developer files if you use Xcode, simulators, npm or Homebrew. See freeing up space on a developer Mac.

Avoid one-line Terminal commands from forums that use sudo rm -rf on system folders. They can't be undone, they skip the Trash, and they can remove files macOS or your apps still need.

Clear it with Disklumo

Disklumo's Clean scan lists caches, logs, developer files, AI tool caches and leftovers from apps you've uninstalled, with the size and full path of every item. You choose what goes, and by default it goes to the Trash. Files in use, or that changed after the scan, are skipped.

System Data items need administrator rights: Disklumo asks for your Mac password for that run only and removes the access when it ends. Those items are deleted directly rather than moved to the Trash, and the confirmation tells you so before anything happens.

Questions

Why is System Data so big on my Mac?

System Data collects everything macOS can't put in another category: caches, logs, Time Machine local snapshots, iPhone backups, developer files and virtual memory. Developer tools and old device backups are the most common reason it reaches tens of gigabytes.

Is it safe to delete System Data?

Not as a whole. Caches, old logs, old device backups and developer build files are safe to clear, and apps rebuild caches when needed. Swap files, the sleep image and anything in the System folder should be left to macOS.

Do it in one window

Disklumo scans your Mac, shows every item with its size and path, and moves what you choose to the Trash. Clean, uninstall apps, map your disk, watch live status and run maintenance. $17 once, for Apple Silicon Macs on macOS 14 or later.

See Disklumo