How to Clear System Data on Mac and Free Up Storage Space
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Quick answer: To clear System Data on a Mac, open System Settings → General → Storage, then remove the files macOS lumps into "System Data": caches, old logs, Time Machine local snapshots, iOS/iPadOS device backups, mail and message attachments, unused language files, and leftover app support files.
On most Macs this reclaims anywhere from a few gigabytes to 30 GB or more. You can do it manually with the steps below, or automate the safe parts with a dedicated cleaner like Purgy.
Does your Mac's storage bar show a large orange block labeled System Data, sometimes called "Other"? It is one of the most common storage complaints on macOS, and Apple shows you almost nothing about what is inside it.
This guide explains what System Data really is, why it grows, and the exact steps to shrink it safely. It is based on cleaning up dozens of Macs running everything from macOS Ventura to macOS Tahoe (26).
What is "System Data" on a Mac?
System Data is a catch-all category in macOS storage that holds everything the system can't neatly file under Apps, Documents, Photos, Music, Mail, or macOS itself. In practice, it's a mix of temporary and support files that accumulate as you use your Mac.
Typical contents of System Data include:
- Caches. app, system, and browser caches that speed things up but grow indefinitely.
- Logs and diagnostic reports generated by macOS and your apps.
- Time Machine local snapshots stored on your internal drive between backups.
- iOS and iPadOS device backups created when you sync an iPhone or iPad.
- Mail and Messages attachments downloaded and stored locally.
- Application support files and plug-ins left behind by installed (and uninstalled) apps.
- Unused language files, fonts, and old software update installers.
- Virtual memory / swap and other temporary system files.
A healthy System Data figure is usually somewhere between 10 GB and 25 GB. If yours has passed 50 GB, or is still climbing, something is holding on to files it no longer needs and it is worth cleaning.
Why does System Data get so large?
System Data grows because macOS is designed to keep things you might need close at hand, and it doesn't always clean up after itself.
The biggest culprits are usually caches that never get purged, Time Machine snapshots that quietly sit on your internal drive, and old device backups you forgot about.
Heavy browser use, large mail accounts, and developer tools like Xcode (which can hoard tens of gigabytes of derived data and simulators) accelerate the problem.
It's also partly a reporting quirk: macOS sometimes takes a while to recalculate storage after you delete files, so System Data can look larger than it truly is until the system catches up. Restarting your Mac often forces a fresh, more accurate calculation.
How to check your System Data usage
- Click the Apple menu in the top-left corner and choose System Settings.
- Select General in the sidebar, then click Storage.
- Wait a few seconds for the color-coded bar to load, then hover over the segments to find System Data.
On older versions of macOS the path is Apple menu → About This Mac → Storage → Manage. Either way, this screen is your starting point and also offers Apple's built-in recommendations, such as storing files in iCloud and automatically emptying the Trash.
How to clear System Data on Mac: 9 safe methods
Work through these in order. The first few are the safest and often free the most space, so you may not need all nine.
1. Restart your Mac first
Before deleting anything, restart. macOS clears certain temporary files and swap data on reboot and recalculates storage. In many cases System Data drops several gigabytes on its own, and you'll get an accurate number to work from.
2. Clear user and app caches
Cache files are the largest and safest slice to trim. In Finder, choose Go → Go to Folder and enter ~/Library/Caches.
Open individual app folders and delete their contents (not the folders themselves). Leave anything you're unsure about. Apps rebuild caches automatically, so nothing is permanently lost , but never delete from /System.
3. Remove old Time Machine local snapshots
Even with Time Machine turned off, macOS keeps local snapshots on your internal drive. They usually purge themselves, but you can speed things up.
Open Terminal and run tmutil listlocalsnapshots / to see them, then delete a specific one with tmutil deletelocalsnapshots <snapshot-date>. This alone can free 10–20 GB on a busy Mac.
4. Delete old iOS and iPadOS backups
If you've ever backed up an iPhone or iPad to your Mac, those backups live in System Data. In the Finder sidebar, select your connected device, click Manage Backups, and remove the ones you no longer need. Backups can easily run 5–50 GB each.
5. Clean up Mail and Messages attachments
Mail downloads and stores attachments locally. In Mail, review large messages and remove attachments you don't need, or re-download them only when required. In Messages, delete old conversations with heavy photo and video threads.
6. Empty the Trash (and app-specific trashes)
Right-click the Trash and choose Empty Trash. Remember that some apps, including Photos, Mail and many editors, keep their own "Recently Deleted" folders that must be emptied separately before the space is actually reclaimed.
7. Remove unused languages, fonts, and old installers
Downloaded macOS installers (multi-gigabyte files often named Install macOS…) frequently hide in your Applications or Downloads folder after an update. Delete them once you've upgraded. Old, unused fonts and language packs can also be trimmed.
8. Clear developer files (Xcode users)
If you write code, Xcode is often the single biggest contributor to System Data. Clear ~/Library/Developer/Xcode/DerivedData and remove unused simulators via Xcode → Settings → Platforms. This routinely recovers 20 GB or more.
9. Use a dedicated cleaner to automate the safe parts
Manual cleanup works, but it's slow, It is also easy to miss files buried deep in the Library folders, or to delete something you should not.
A purpose-built Mac cleaner scans these locations for you, shows exactly what's safe to remove, and clears it in one pass.
This is precisely the problem we built Purgy to solve.
Purgy is a lightweight macOS disk cleaner that scans the folders where System Data hides, including caches, logs, leftover app support files and forgotten large files, and lets you reclaim that space with a clear, reviewable list rather than guesswork.
If you are weighing it against other tools, our Mac cleaner comparison puts them side by side.
How much space can you expect to recover?
Results vary by how you use your Mac, but as a rough guide from real cleanups: caches typically return 2–10 GB, Time Machine local snapshots 10–20 GB, old device backups 5–50 GB, and Xcode derived data 20 GB+ on developer machines.
A thorough pass on a Mac that's never been cleaned often frees 30–60 GB in total.
What you should never delete
Cleaning System Data is safe if you stay out of protected areas. Do not delete anything inside the /System folder, and don't remove files from ~/Library unless you understand what they do.
Avoid cleaners that promise miracles and then delete without showing you what they are removing. They can break apps or macOS itself. When in doubt, back up with Time Machine first, and only remove caches, logs, and clearly identifiable leftovers.
How Purgy clears System Data
Purgy's System Data screen splits the grey bar from Storage settings into rows you can act on, each with its size:
- System caches and Dev junk: app caches, logs, Xcode build data and package-manager caches. They rebuild on their own, are ticked by default and are freed with one click.
- APFS snapshots and Old iOS backups: listed for you to review and never ticked for you. Backups move to the Trash; snapshots are removed with Apple's
tmutil, only if you tick them. - Unused AI models: model files from Ollama, LM Studio, GPT4All and similar tools, moved to the Trash only if you choose them.
- Real data, keep: Mail, Messages and shared app data, measured so you know their size and never deleted.
- macOS's own assets: Apple Intelligence models, voices and other files inside the protected system. No app can delete these, so Purgy names them and points to the setting that controls them.
Old macOS installers in Downloads and Applications are found too, and Purgy's Trash screen empties the Trash after asking. You can see what your own System Data is made of with the free trial.
Frequently asked questions
These are the questions people ask most about System Data, with short answers.
Is it safe to delete System Data on Mac?
Yes, the removable parts of System Data are safe to delete: caches, logs, old backups, snapshots and installers. The essential parts macOS needs are protected and can't be removed through normal cleanup. Stick to caches, logs, and backups, and avoid the /System folder.
Why is my System Data so large all of a sudden?
A sudden jump usually points to a new device backup, a large Time Machine local snapshot, a macOS update installer, or a cache that grew quickly (often a browser or a developer tool). Restart first, then check backups and snapshots.
Why won't my System Data go down after deleting files?
macOS can take time to recalculate storage. Restart your Mac to force a fresh calculation. If it still won't drop, look for Time Machine local snapshots or app-specific "recently deleted" folders that haven't been emptied.
Does clearing cache slow down my Mac?
Only briefly. Apps rebuild the caches they need the next time you use them, so you may notice a one-time slowdown before things return to normal. You get the free space back in exchange.
What's the easiest way to keep System Data under control?
Restart regularly, empty trashes, and run a cleanup pass every month or two. If you'd rather automate it, a native cleaner like Purgy handles the recurring, safe-to-remove files so System Data doesn't creep back up.
The bottom line
System Data is not a bug. It is what everyday Mac use leaves behind. You can shrink it in minutes by restarting, clearing caches, and removing old snapshots and backups.
A dedicated tool does the same work without the manual steps. Either way, the space is yours to take back.
Still short on storage after a cleanup? Try Purgy to see exactly what is using your disk, then clear it safely in one pass.