Mac System Data too large? What it is and how to shrink it safely

What System Data actually is#

In System Settings › General › Storage, macOS sorts files into categories such as Applications, Documents, Photos and iOS Files. Apple's own definition of System Data is "a general category that measures the storage space used by all Apple and third-party files that don't belong to any more specific category." On older versions of macOS the same bar was called Other.

That covers a lot of different things:

• App caches in ~/Library/Caches and /Library/Caches
• Logs in ~/Library/Logs and /private/var/log
• Developer tools: Xcode device support files, build data and simulators in ~/Library/Developer
• Virtual memory: swap files the Mac writes when RAM is full
• Time Machine local snapshots, kept on the internal disk
• App support data for apps that store databases, models or offline content

Because it is a mix, there is no single "clear System Data" button. You find which part is big, then deal with that part.

Find which part is big#

System Settings does not break System Data down. Terminal does, and the command below only reads:

du -sh ~/Library/* 2>/dev/null | sort -rh | head -10

Some folders, such as iPhone backups in ~/Library/Application Support/MobileSync, are protected: Terminal gets "Operation not permitted" unless it has Full Disk Access in System Settings › Privacy & Security, and the command above skips them without saying so. Finder can still open them.

On our test Mac (MacBook Pro, macOS 26.3) the top of that list was:

If the Developer folder is near the top, go straight to why Xcode takes so much space. If Caches is near the top, see whether Library caches are safe to delete.

5 safe ways to shrink System Data#

1. Restart the Mac#

Swap files and many temporary caches are removed when the Mac restarts. It costs nothing, so do it first and check Storage again a few minutes after login.

2. Clear developer files#

Xcode keeps a copy of debugging symbols for every iOS version of every device you have plugged in. These sit in ~/Library/Developer/Xcode/iOS DeviceSupport and are safe to delete; Xcode copies them again the next time that device connects. Build data in DerivedData is also safe to delete. Details and commands are in the Xcode space guide.

3. Clear your own app caches#

Quit the app first, then remove its folder inside ~/Library/Caches. Apps rebuild what they need. For browsers, use the browser's own clear-cache setting instead, so it does not get confused while running.

4. Delete old iPhone and iPad backups#

Click ⓘ next to iOS Files in System Settings › General › Storage and delete backups of devices you no longer use. Backups are not counted under iOS Files on every macOS version, so if the list is empty, check ~/Library/Application Support/MobileSync/Backup in Finder with ⇧ ⌘ G.

5. Remove old Time Machine local snapshots#

List them with:

tmutil listlocalsnapshots /

If the list is long, follow how to delete Time Machine local snapshots. Apple notes that macOS counts snapshot space as available, so snapshots rarely block a download, but they do make the Storage bar look full.

Don't delete these: /System, /Library/Apple, /private/var/db, /private/var/vm while the Mac is running, or the ~/Library/Containers folders of apps you still use. Removing them can break macOS or wipe an app's data.

Does this apply to my Mac?#

If System Data is still large after these steps, start again from the full storage checklist and look at what else is big.