Guide · 5 min read
What is “System Data” storage on a Mac (and how to shrink it)
Open System Settings → General → Storage and you'll often see a huge grey “System Data” bar (it used to be called “Other”). It's vague on purpose. Here's what's really in it and how to bring it down.
What System Data actually contains
System Data is everything macOS can't neatly file under Apps, Photos, Music and so on. In practice it's mostly:
- App and system caches (~/Library/Caches and more)
- Logs and diagnostic reports
- Local Time Machine snapshots (purgeable)
- Browser caches and downloads
- Old iOS device backups and updates
- Developer build artifacts (node_modules, DerivedData) for some users
Why it gets so big
These files are created constantly and rarely cleaned up. Caches in particular grow without limit until something clears them, and local snapshots accumulate whenever your Time Machine drive isn't connected.
How to shrink it safely
- Clear app caches in ~/Library/Caches (safe - apps rebuild them)
- Remove local snapshots (see our purgeable-space guide)
- Delete old iOS backups in ~/Library/Application Support/MobileSync/Backup
- Empty the Trash and clear Downloads
- Developers: clear build folders (node_modules, DerivedData)
The fast way
TidyBar scans exactly these categories at once and shows what's reclaimable for free, then clears it to the Trash so it's recoverable. It turns the vague “System Data” bar into a clear, actionable list.
FAQ
Is it safe to delete System Data?+
The reclaimable parts are - caches, logs, snapshots and build artifacts all regenerate. Don't try to delete the System Data bar directly; remove the underlying items instead.
Why is my System Data so large?+
Usually accumulated caches, local Time Machine snapshots, old device backups, and (for developers) build folders that were never cleaned up.
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