How to clear System Data on your Mac.

First, look at what you have

Open System Settings › General › Storage. The colored bar at the top splits your disk into categories, and System Data is usually the gray slice near the end. Hover over it to see its size.

Storage settings won't tell you what's inside, and its number can lag behind reality. Give it a minute after opening, and don't panic if it jumps around.

What's inside System Data

• Local Time Machine snapshots. If you use Time Machine, macOS keeps hourly snapshots on your Mac between backups. They can take 30 to 60 GB. macOS counts them as purgeable and removes them after 24 hours or when space runs low, but Storage settings may show them in the meantime.
• Purgeable space. Files macOS has already marked as reclaimable, like iCloud copies it can download again. It's freed on demand, so it isn't really in your way.
• Simulators and runtimes. If you've ever installed Xcode, iOS and watchOS simulator runtimes can take tens of gigabytes, including ones for versions you no longer test on.
• Caches and logs. Apps and package managers keep downloaded and generated files so they don't have to fetch or build them again. They come back on their own.
• Apple Intelligence models. On Macs that support it, the on-device models live on your disk.
• The Spotlight index. Your search index, which can grow out of date and larger than it needs to be.
• Docker and virtual machines. Docker keeps its images and build cache in one large disk image, and VM apps do something similar.

How to clear it, step by step

In order of how much space each step usually frees for the least risk. Commands go in Terminal. Read each one before you run it.

1. Restart your Mac. It clears temporary files and swap, and Storage settings recalculates. Free, and sometimes enough.
2. Remove local Time Machine snapshots. List them, then delete by date:

   tmutil listlocalsnapshots /
   sudo tmutil deletelocalsnapshots 2026-10-05-093012

   Replace the date with one from the list. Time Machine keeps taking new ones, and macOS removes each after 24 hours anyway, so this is for when you need the room right now. Recent macOS versions no longer let you turn local snapshots off with tmutil disablelocal.
3. Delete simulator runtimes you don't use. Remove simulators for runtimes no installed Xcode supports:

   xcrun simctl delete unavailable

   To remove whole runtimes, list them and delete by identifier, or use Xcode › Settings › Components:

   xcrun simctl runtime list
   xcrun simctl runtime delete <identifier>

4. Clear caches. Quit your apps, then in Finder choose Go › Go to Folder and open ~/Library/Caches. Move folders for apps you know to the Trash; they'll rebuild. Do the same for Xcode's build data in ~/Library/Developer/Xcode/DerivedData. Package managers clear their own caches:

   npm cache clean --force
   pnpm store prune
   pip cache purge

   Each tool downloads what it needs again on the next install.
5. Prune Docker. If you use Docker, its own command removes stopped containers, unused networks, dangling images, and build cache:

   docker system prune

   Add -a to also remove images no container is using. You'll download them again the next time you need them.
6. Turn off Apple Intelligence, if you don't use it. In System Settings › Apple Intelligence & Siri, switch it off, and macOS can remove the on-device models. Turn it back on any time; they'll download again.
7. Rebuild the Spotlight index. If it's grown large, rebuilding often shrinks it:

   sudo mdutil -E /

   Search results will be incomplete for a while as it re-indexes.
8. Leave purgeable space alone. macOS frees it the moment something needs the room. Apps that “free” it for you are only doing what macOS would have done anyway.

What not to touch

• Anything under /System. It's on a sealed, read-only volume for a reason.
• /private/var/vm. That's swap and the sleep image, managed by macOS. Deleting files there by hand can crash your Mac.
• Random folders in /Library. If you don't know what installed it, look it up before you remove it.
• Apps that promise a performance miracle. On an SSD, free space doesn't change how a Mac runs until the disk is nearly full. Reclaim space when you need room, not for a mystery gain.