What is “System Data” on a Mac, and how do you clear it?

Open Storage settings on almost any Mac and you'll find a large grey slice called System Data — often 50, 100 or even 200 GB. It isn't one thing, and it isn't macOS itself. It's everything macOS can't neatly file under Apps, Documents or Photos. Here's what usually lives there and how to shrink it.

What counts as System Data

macOS puts a file in System Data when it doesn't belong to one of the other categories. In practice that means:

• Caches — app and browser caches in ~/Library/Caches and inside sandboxed apps' containers.
• Logs — ~/Library/Logs, /Library/Logs and /var/log.
• Time Machine local snapshots — hourly snapshots kept on your Mac while your backup disk is away.
• iPhone and iPad backups and software updates saved by Finder.
• Developer files — Xcode DerivedData, simulators, device support files, Docker images and package-manager caches.
• Virtual memory — swap files and the sleep image macOS uses for hibernation.
• Hidden folders in your home folder such as ~/.npm, ~/.gradle or ~/.cache.

Step 1: find out which part is big

Storage settings won't break System Data down, so you need to look at folders directly. In Finder, press ⇧⌘G and go to ~/Library, then use View › Show View Options › Calculate all sizes in list view to sort folders by size. Press ⇧⌘. in your home folder to reveal hidden folders too.

This works but is slow. SpaceSweep's Storage Explorer does the same thing in one pass: it lists your home folder by size — hidden folders included — and lets you drill into any of them.

Step 2: check Time Machine local snapshots

If you use Time Machine, macOS keeps local snapshots on your internal disk. They're deleted automatically when space runs low, but they still inflate System Data. To list them, open Terminal and run:

tmutil listlocalsnapshots /

To delete one, copy its date stamp from that list:

sudo tmutil deletelocalsnapshots 2026-11-08-101530

Snapshots are a safety net. Delete them only if you need the space now; macOS removes them on its own when it has to.

Step 3: clear caches and logs

Caches are the most common reason System Data balloons, especially browser and creative-app caches. Quit the app first, then delete the contents of its folder in ~/Library/Caches — not the folder itself. Logs in ~/Library/Logs can go too. Read is it safe to delete cache files? for which ones to leave alone.

Step 4: remove old device backups and updates

In Finder, select your iPhone or iPad in the sidebar and click Manage Backups… to delete backups you don't need. iOS software update files can also sit in ~/Library/iTunes; it's safe to delete .ipsw files there, as Finder downloads a fresh one when you next update.

Step 5: clear developer files

For anyone who has installed Xcode, this is usually where the space is. DerivedData, old simulator runtimes and iOS DeviceSupport can easily reach 50 GB. Follow our guide to deleting Xcode DerivedData and other Xcode junk. Docker users can reclaim space with docker system prune.

Step 6: restart

A restart clears swap files and some temporary data, and gives macOS a chance to recalculate the storage bar. It's normal for System Data to shrink a bit after a restart and then grow back by a few gigabytes as you work.

See what's inside System Data

SpaceSweep's Storage Explorer finds the hidden folders macOS lumps into System Data, and its cleanup clears caches, logs and Xcode junk safely.

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