How to clear System Data on your Mac

You open System Settings → General → Storage and the biggest slice of the bar is a grey block called System Data, sometimes 50 GB or more, with no way to see what is inside. Here is what System Data on a Mac really is, which parts are safe to clear, and how to clear them without breaking anything.

What is System Data on a Mac?

System Data is the catch-all category for everything macOS doesn't file under Applications, Documents, Photos and the other named categories. On macOS Big Sur and earlier it was called Other. It typically includes:

• Caches that apps and browsers keep to load faster, in ~/Library/Caches and inside app containers.
• Logs and crash reports in ~/Library/Logs.
• Time Machine local snapshots of your startup disk.
• Virtual memory swap files and the sleep image macOS writes when your Mac sleeps.
• App support files, plug-ins and data, including leftovers of apps you already deleted.
• Developer data: Xcode DerivedData, simulators and device support, package manager caches.
• Virtual machine and container disks, such as the Docker Desktop disk image.

Why is System Data so big?

A few of those items can grow quietly to tens of gigabytes. Browser and app caches rarely shrink on their own, Time Machine keeps hourly local snapshots, and a single Docker disk image or a year of Xcode builds can take more room than all your documents. macOS also takes a while to recalculate the bar, so System Data can look bigger right after you delete things.

How to see what is inside System Data

The Storage screen only shows a total. To see where it goes, open Finder, press Shift Command G and go to ~/Library. Switch to list view, choose View → Show View Options, turn on Calculate all sizes and sort by Size. Folders such as Caches, Developer, Containers and Application Support usually stand out.

If you are comfortable with Terminal, du -sh ~/Library/* | sort -h lists the same folders by size.

How to clear System Data safely

1. Restart your Mac. Swap files and temporary files are cleared on restart. It is free and often recovers a few gigabytes.
2. Delete caches and logs. Quit the apps first, then delete the contents of their folders in ~/Library/Caches and ~/Library/Logs. Clear browser caches from each browser's settings.
3. Remove Time Machine local snapshots. They are safe to delete and don't affect the backups on your backup disk. See how to delete Time Machine local snapshots.
4. Clear developer data. Delete ~/Library/Developer/Xcode/DerivedData, run xcrun simctl delete unavailable, and run docker system prune if you use Docker. Package managers have their own clean commands, such as npm cache clean --force and brew cleanup.
5. Delete old iPhone and iPad backups and updates. In Storage, click the ⓘ next to iOS Files.
6. Remove leftovers of apps you deleted. Look in ~/Library/Application Support and ~/Library/Containers for folders named after apps that are no longer installed.
7. Give macOS a few minutes. The Storage bar updates in the background. Reopen it after a short while to see the new total.

What you should never delete

• The System Data category as a whole: there is no single folder to delete, and parts of it are needed.
• Anything in /System, /private/var or /Library that you don't recognise.
• Support files and containers of apps you still use: they hold settings, logins and data.
• Keychains, Mail, Messages and Photos libraries.

Clear System Data with Roomy

Roomy breaks System Data into items you can understand. System Junk finds caches, logs, crash reports and old temporary files, Developer finds Xcode data and package caches, the uninstaller finds leftovers, and Optimize thins Time Machine local snapshots. Every row says what goes and what stays, only rebuildable data is selected for you, and every path is checked again before anything is removed.

Frequently asked questions