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What is “System Data” on a Mac and how to shrink it

Guide · Fabian Faraz Farid · 04.11.2026

In System Settings › General › Storage, macOS shows a bar with categories. One grey part is called “System Data”, and it is often surprisingly large. macOS does not say what is inside. Here is what usually is, and what you can do yourself.

What counts as “System Data”

“System Data” is not a folder. It is the rest: everything macOS does not assign to another category such as Applications, Documents or Photos. Typical items:

  • Caches of apps and macOS, mostly in ~/Library/Caches.
  • Logs in ~/Library/Logs and /Library/Logs.
  • Local Time Machine snapshots, when Time Machine is on.
  • iPhone and iPad backups made with Finder.
  • Developer data: Xcode, simulators, package caches of Homebrew, npm or pip, the Docker Desktop disk image.
  • Virtual memory (swap files) and the sleep image, which macOS manages itself.

Depending on the macOS version, the storage view shows some of these in their own categories. Whatever is left ends up in “System Data”.

Shrink it by hand, step by step

  1. Restart. macOS clears temporary and swap files on the way. Then check again.
  2. Look at local snapshots. In Terminal, tmutil listlocalsnapshots / lists them. macOS removes them on its own when space runs low. More in the guide to local snapshots.
  3. Remove old iPhone backups. Connect the device or select it in the Finder sidebar, then under General choose “Manage Backups…”. Keep the newest backup of every device you still use.
  4. Check caches. In Finder choose Go › Go to Folder and enter ~/Library/Caches. Folders named after apps are rebuilt by those apps when needed. Quit the app first. Do not remove the Caches folder itself.
  5. Clean developer data if you use Xcode: see Xcode takes too much space. Shrink Docker Desktop in its own settings, never by deleting the disk image file.
  6. Empty the Trash. Deleted files take space until the Trash is emptied.

Leave these alone

Folders like /System, /usr, /private/var and ~/Library/Mobile Documents (iCloud Drive) do not belong in the Trash. And part of System Data is macOS itself. No app can see inside that part or shrink it in a useful way.

Where Searoom helps

Searoom breaks System Data down: caches, logs, Mail attachments, iPhone and iPad backups, local snapshots, Xcode, simulators, Docker, package caches and “macOS and the rest”. Every item has its size and one sentence on what it is and whether you can safely remove it. Where macOS does not tell a size, as with snapshots, it says “not disclosed”. What you clean up goes to the Trash, and you can put it back from Cleaned Up.

Searoom explains every storage item on your Mac in one sentence, only moves things to the Trash, removes apps with their leftovers and keeps your apps updated. 14 days with everything, then a free version stays, Pro is €29 once.

See Searoom

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