Clear "System Data" on Mac the safe way.
System Data is often the biggest — and least explained — bar in your Mac’s storage view. Here is what is actually inside it, and how to shrink it without breaking anything.
Download Free for MacQuick answer
You can’t delete “System Data” as one thing, but you can shrink it: remove old Time Machine local snapshots, clear app caches and logs in ~/Library, delete old iPhone/iPad backups, clear Xcode and other developer data, and restart to drop temporary swap files. Check the result in System Settings → General → Storage.
What is usually inside System Data
Time Machine local snapshots
Managed by macOS; listed with tmutil
App caches
~/Library/Caches
Logs and diagnostic reports
~/Library/Logs
iPhone and iPad backups
~/Library/Application Support/MobileSync/Backup
Xcode, simulators and other developer data
~/Library/Developer
Leftovers from deleted apps
~/Library/Application Support, ~/Library/Containers
Swap and temporary files
Created by macOS while it runs; cleared on restart
Step by step: reduce System Data manually
Work top to bottom — the first steps usually free the most space. Quit apps before clearing their caches.
1. See what macOS reports
Open System Settings → General → Storage and wait for the bar to finish calculating. Note the System Data size so you can measure the result.
2. Remove old Time Machine local snapshots
If you use Time Machine, macOS keeps local snapshots on your disk and counts them in System Data. List them, then delete the ones you don’t need using the date part of each name (macOS also removes them automatically when space runs low).
tmutil listlocalsnapshots / sudo tmutil deletelocalsnapshots 2026-10-01-1200003. Clear app caches
In Finder choose Go → Go to Folder…, enter ~/Library/Caches, and move the folders of apps you use heavily (browsers, Spotify, Slack, Adobe…) to the Trash. Apps rebuild what they need.
4. Delete old logs
Go to ~/Library/Logs and remove old log folders and DiagnosticReports. They are only useful for troubleshooting.
5. Delete old iPhone and iPad backups
Connect your iPhone or iPad, select it in the Finder sidebar, click Manage Backups and delete the backups you no longer need. Without the device, open ~/Library/Application Support/MobileSync/Backup and move old backup folders to the Trash. A full backup can be tens of gigabytes.
6. Clear Xcode and simulator data (developers)
DerivedData and old simulators are safe to remove; Xcode recreates what it needs.
rm -rf ~/Library/Developer/Xcode/DerivedData xcrun simctl delete unavailable7. Remove leftovers from apps you deleted
Check ~/Library/Application Support and ~/Library/Containers for folders named after apps you no longer have, and move them to the Trash.
8. Empty the Trash and restart
Nothing is freed until the Trash is emptied. A restart then clears swap and temporary files. Re-check Storage — the System Data figure can take a few minutes to update.
Don’t delete these
- Anything inside /System, /Library/Apple or /private — macOS protects these for a reason.
- Your Keychains (~/Library/Keychains) and Preferences (~/Library/Preferences).
- Containers of apps you still use — that is where their documents and settings live.
The faster way: let MacDiskCleaner find it
- 01
See the real breakdown
One scan lists the caches, logs, developer data and app leftovers that make up System Data — with sizes.
- 02
Pick what goes
Safe items are labelled; anything that needs a second look is marked Review first and left unselected.
- 03
Clean safely
Everything goes to the Trash first, and protected system paths are blocked, so nothing important can be lost.
Why is System Data so big (100 GB+)? Read the full explainer
Frequently asked questions
What exactly is "System Data" on a Mac?
It’s the catch-all category in Storage for anything that isn’t Applications, Documents, Photos, iCloud Drive or another named category: caches, logs, Time Machine local snapshots, device backups, developer data, app support files and temporary files.
Can I clear System Data on Mac?
Not as a single item, but you can safely reduce it by removing what it is made of: old local snapshots, caches, logs, device backups, developer data and app leftovers. Never delete files inside /System or your Keychains.
Why is my System Data over 100 GB?
Usually one or two culprits: Time Machine local snapshots that haven’t been purged, several old iPhone/iPad backups, or Xcode and simulator data. Check those three first.
Does restarting reduce System Data?
Yes, a little: a restart clears swap and some temporary files, and gives macOS a chance to purge snapshots it no longer needs. It won’t remove caches, backups or developer data.
Is it safe to delete ~/Library/Caches?
Clearing the cache folders of individual apps is safe — they are rebuilt automatically, though the app may be slower the first time. Quit the app first, and move the folders to the Trash instead of erasing them.
Why does System Data keep growing back?
Caches, logs and snapshots regenerate as you use your Mac. That’s normal; a cleanup every month or two keeps it in check, and MacDiskCleaner Pro can scan on a schedule.
See what’s really inside your System Data
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Version 1.1.2 · 4.8 MB · macOS 14 or later · Apple Silicon & Intel