How to Clear System Data on Mac Safely

System Data, in System Settings › General › Storage, is everything macOS doesn't count in another category: caches, logs, local Time Machine snapshots, virtual memory files, iPhone and iPad backups, developer files and app support data. There's no single button to clear it. To shrink it, remove the safe parts one at a time, starting with old device backups, developer data, local snapshots and caches, and leave the system folders alone.

What System Data is

Open System Settings › General › Storage. The bar at the top shows categories like Applications, Documents, Photos and macOS. System Data is the bucket for everything else. It commonly includes:

Caches for apps, browsers and macOS.
Logs and crash reports.
Time Machine local snapshots, which Time Machine keeps on your Mac between backups.
Virtual memory: swap files and the sleep image.
iPhone and iPad backups made with Finder.
Developer data: Xcode build files, simulators, Docker's disk image and package caches.
App data in the Library folder that isn't a document, such as downloaded assets or virtual machines.

The number moves up and down as macOS creates and removes snapshots, caches and swap. macOS doesn't show what's inside System Data, which is why it's confusing. The sections below go through the parts you can safely reduce.

What's safe to remove

Old iPhone and iPad backups

Device backups made in Finder can each take many gigabytes, and backups of phones you no longer have often stay for years.

Connect the iPhone or iPad, open Finder and select the device in the sidebar.
In the General tab, click Manage Backups.
Select a backup you no longer need and click Delete Backup.

Don't delete files inside the backup folder by hand. A partial backup can't be restored.

Time Machine local snapshots

If you use Time Machine, macOS keeps local snapshots on your startup disk so you can restore files when the backup disk isn't connected. macOS removes them on its own, usually within a day, and sooner when it needs the space. To remove them now:

Open Terminal.
List them:

   tmutil listlocalsnapshots /

Delete one by its date, using a date from the list:

   sudo tmutil deletelocalsnapshots 2026-10-08-093015

Your backups on the backup disk aren't affected.

Caches

Your caches live in ~/Library/Caches. Apps rebuild them as needed, so removing them is safe once the app is closed. How to clear cache on Mac covers the safe method, including browser caches.

Xcode and simulator data

If you build apps, developer files are often the largest part of System Data.

DerivedData (~/Library/Developer/Xcode/DerivedData) is build output. It's safe to delete; Xcode rebuilds it. Quit Xcode first.
iOS DeviceSupport (~/Library/Developer/Xcode/iOS DeviceSupport) holds files for each iOS version you've connected. It's safe to delete and comes back when you connect a device.
Archives (~/Library/Developer/Xcode/Archives) are builds you've distributed. Keep the ones you need for reading crash reports.
Simulators: run xcrun simctl delete unavailable to remove simulators for iOS versions you no longer have. Remove simulator runtimes you don't use in Xcode › Settings › Components.

Other developer data

Docker: docker system prune removes stopped containers, unused networks and dangling images. Stopped containers are deleted for good, so check first.
Homebrew: brew cleanup removes old versions and downloads.
npm, pnpm, Yarn and pip caches: see the developer section of the cache guide.

Logs and crash reports

~/Library/Logs and /Library/Logs hold logs and crash reports. They're usually small. Old crash reports in ~/Library/Logs/DiagnosticReports are safe to delete; leave the folders themselves in place.

Data from apps you deleted

Dragging an app to the Trash leaves its data behind in ~/Library/Application Support, ~/Library/Caches and similar folders. If you're sure the app is gone for good, its folders there are safe to remove. When an app is still installed, remove its data through the app's own settings instead.

What not to touch

/System and the macOS volume. They're protected, and changing them can stop the Mac from starting.
/private/var/vm. Swap files and the sleep image. macOS manages them; a restart shrinks swap.
/private/var/db and other folders under /private. System databases.
The ~/Library folder as a whole. Remove specific items you understand, never the folder.
Containers and Group Containers in ~/Library. They hold app data, including settings and sometimes your documents.
Mail and Messages data. Remove attachments from inside those apps.

Avoid copying sudo rm -rf commands from forums. One typo can delete things you can't get back. Moving files to the Trash first gives you a way back.

Why System Data doesn't drop right away

After cleaning, empty the Trash. The Storage view can take a while to recalculate. If swap was large, a restart frees that space too. Snapshots and caches come back over time as you use the Mac, which is normal. What you're removing for good is the old backups and the stale developer files.

If System Data keeps growing fast, something specific is filling it: often a virtual machine, Docker, an app's downloads or simulator data. A storage scan that names each folder, like the one in our Mac cleaner, helps you find it.

Clear System Data with SystemWatch

SystemWatch's Storage scan breaks your disk into items you can act on: app caches, logs, developer files, iPhone and iPad backups, leftovers from deleted apps, old installers in Downloads and large files. Each item comes with what it is and whether it's safe to remove. Items that rebuild themselves are marked safe. Things that might matter to you, like backups and archives, are marked for review. Sandboxed app data is shown so you understand the space, but never offered for removal.

Cleaning moves items to the Trash, and you can put them back from Cleanup History. Nothing is removed until you confirm.

App Store edition: the scan is free. One-click cleanup with undo is part of SystemWatch Pro.
Website edition: adds Deep Clean with Full Disk Access. It handles Time Machine local snapshots, the Trash, Homebrew, old simulators, Docker, and npm, pnpm, Yarn and pip caches. These steps can't go through the Trash, so each one says what it removes and asks before it runs.