CleanLoupeYou can't clear System Data on a Mac with one button, because it isn't one thing. It is the Storage category for everything macOS doesn't file under Apps, Documents, Photos and the rest: local Time Machine snapshots, caches, logs, iPhone backups, virtual machine disks and developer files. To shrink it, find which of those parts is large on your Mac and deal with that part.
Below is how to identify each piece, which are safe to remove, and which macOS will handle for you.
Why System Data looks so big
Open System Settings › General › Storage and you will see System Data in the bar and in the list. Unlike Applications or Documents, it has no ⓘ button, so you can't browse it from there. That is deliberate: the category is calculated as "used space that doesn't fit another category", not as a folder you can open.
That also explains why it jumps around. After a large macOS update, Spotlight and Photos re-index, temporary files come and go, and the number can change by gigabytes within hours without you doing anything. Before you start deleting, restart the Mac and look again the next day. Sometimes the problem shrinks on its own.
Here is what usually ends up counted as System Data:
- Local Time Machine snapshots
- Caches in
~/Library/Cachesand/Library/Caches - Logs and diagnostic reports
- iPhone and iPad backups in
~/Library/Application Support/MobileSync/Backup - iOS update files downloaded by Finder
- Virtual machine and container disk images
- Xcode and other developer tool data under
~/Library/Developer - Swap and sleep image files managed by macOS (leave these alone)
Step 1: Rule out local snapshots
If Time Machine is turned on, macOS keeps local snapshots on your internal disk. They count toward used space, and they are a common reason System Data looks large right after big file changes. List them in Terminal:
tmutil listlocalsnapshots /
macOS keeps these for about 24 hours and removes them by itself when the disk needs room, so they are rarely a long-term problem. If you need space right now, you can thin them. The details, including the exact tmutil commands and why the Finder "purgeable" number relates to them, are in purgeable space on Mac explained.
Step 2: Find the large folders in your Library
Most of the System Data you can actually act on lives in your user Library. Show it in Finder with Go › Go to Folder (Shift-Command-G) and type ~/Library. Then measure the usual suspects in Terminal:
du -sh ~/Library/Caches ~/Library/Logs ~/Library/Developer \
~/Library/Containers ~/Library/"Application Support" 2>/dev/null
du -sh ~/Library/* 2>/dev/null | sort -h | tail -15
The second command lists the 15 largest folders inside your Library. Whatever is at the bottom of that list is your lead. Note that ~/Library/Containers and ~/Library/Application Support often hold real app data (mail, chats, documents). A large size there is not a reason to delete; it is a reason to check which app owns it and clean up inside that app.
If Terminal says "Operation not permitted" for some folders, that's macOS privacy protection. Give Terminal Full Disk Access in System Settings › Privacy & Security, or skip those folders.
Step 3: Clear caches and logs
Caches are temporary and rebuild as you use apps. Emptying an app's folder inside ~/Library/Caches is generally fine when the app is quit. Logs in ~/Library/Logs are text files apps write for troubleshooting; old ones can go.
System-wide caches in /Library/Caches and crash logs in /Library/Logs/DiagnosticReports need an administrator password and deserve more care. Which cache folders to leave alone, and why caches grow back, is covered in how to clear cache on Mac.
Step 4: Remove old device backups and update files
Device backups can be one of the largest hidden parts of System Data. Delete them through Finder: connect an iPhone or iPad, select it in the sidebar, click Manage Backups on the General tab, select an old backup and click Delete Backup. Step-by-step instructions, including what to do when the device is no longer around, are in how to delete old iPhone backups on Mac.
While you are there, check for leftover iOS and iPadOS update files. They are only used to restore or update a device over a cable, and Finder downloads them again when needed:
du -sh ~/Library/iTunes/"iPhone Software Updates" ~/Library/iTunes/"iPad Software Updates" 2>/dev/null
Step 5: Check virtual machines and developer data
If you use virtualization or container tools, their disk images are usually big single files, often inside ~/Library/Containers or the app's own folder. Remove virtual machines from inside the app that created them, so its records stay consistent. Docker, for example, has its own cleanup commands and settings; don't delete its data folder by hand while it is running.
For developers, ~/Library/Developer is often the biggest piece of all. Xcode's DerivedData, device support folders, simulators and archives all live there. Measure it:
du -sh ~/Library/Developer/* 2>/dev/null | sort -h
Handling each of those safely is a topic of its own: see freeing disk space on a developer Mac.
If System Data is huge (100 GB+) or keeps growing
A System Data figure of 100 GB or more, or one that grows every day, almost always has a single cause rather than a general buildup. Check these in order:
- Local snapshots that never clear. This often happens when a Time Machine disk hasn't been connected for weeks.
tmutil listlocalsnapshots /lists them; Step 1 above covers thinning them. - A virtual machine or Docker disk image. One file can hold tens of gigabytes. Docker's image only grows until you prune it; see Docker taking up space.
- Device backups and update files (Step 4).
~/Library/Developer, if you use Xcode.- One runaway cache or log folder, often from an app stuck in an error loop.
To catch something that's growing, measure your Library twice, a day apart, and compare:
du -sh ~/Library/* 2>/dev/null | sort -h > ~/Desktop/library-1.txt
# a day later, run it again into library-2.txt, then:
diff ~/Desktop/library-1.txt ~/Desktop/library-2.txt
If the numbers still make no sense, with a full disk and nothing large to find, see why Mac storage numbers don't add up.
What not to touch
Some things counted in System Data should stay:
- Anything under
/System,/private/var/vm(swap and sleep image) or other hidden system folders. macOS manages these and protects most of them. ~/Library/Application Supportfolders of apps you still use, unless you know what's inside.- Apple's own caches for iCloud, Find My, Wallet and similar services. Removing them doesn't save much and can make those services resync.
If System Data is still large after Steps 1 to 5, the remaining space is usually temporary files macOS will release on its own, or data belonging to a specific app you can trace with the du commands above.
How CleanLoupe handles System Data
CleanLoupe doesn't pretend to have a "delete System Data" button. What it does is pull the removable parts of System Data into one reviewable list.
CleanLoupe's Cleanup module proposes app caches in ~/Library/Caches (skipping caches that hold live state like iCloud, Find My and Wallet), app logs in ~/Library/Logs, iOS and iPadOS update files, iPhone and iPad backups (labelled Review, and only with Full Disk Access), system caches in /Library/Caches (Review, with the administrator prompt) and system crash logs. Its developer group adds Xcode DerivedData, device support folders, simulator caches, package manager caches and, while Docker is running, Docker's own prune of unused images, stopped containers and build cache (volumes are kept, and a prune can't be put back). An AI tools group lists caches of AI apps and code editors, and downloaded AI models. Every item carries a Safe, Review or Careful label.
For local snapshots, its Performance module can thin Time Machine local snapshots; backups on your backup drive aren't affected.
Files it removes go to the Trash and appear in History, where Put Back restores it until you empty the Trash. Protected system paths are refused, and items written in the last hour are never preselected.
What it doesn't cover: virtual machine images, Docker's disk image and volumes, simulator runtimes and other app-managed stores. For those, use the app's own cleanup as described above.
FAQ
Why is System Data so large on my Mac?
It collects everything macOS doesn't put in another category, including snapshots, caches, backups, logs and developer files. A large number usually means one of those parts has grown, often device backups, developer data or temporary snapshots after big file changes.
Can I delete System Data on Mac?
Not directly, since Storage settings has no browse button for it. You reduce it by removing its parts: thinning snapshots, clearing caches and logs, deleting old device backups and cleaning developer tools.
Does restarting a Mac reduce System Data?
It can. Restarting clears some temporary files and lets macOS finish background tasks such as removing old snapshots. Check the number again after a restart before deleting anything.
Why did System Data grow after a macOS update?
After a major update, Spotlight and Photos re-index and macOS keeps temporary files for a while. The number often settles over the following hours or days.
Is System Data the same as Other storage?
Yes. macOS 11 Big Sur and earlier called this category Other. macOS 12 Monterey renamed it System Data. The contents and the fixes are the same.
What is the macOS category in Storage, and can I make it smaller?
It's the macOS system itself, kept on a sealed, read-only volume that is about the same size on every Mac running that version. You can't shrink it, and updates replace it. Anything you can reduce is in System Data or the other categories.
Is it safe to delete files in /private/var?
No, leave /private/var alone. It holds swap, sleep image and system state that macOS manages, and deleting from it can cause problems without saving lasting space.
To see the removable parts of your System Data in one list, with an undo, download CleanLoupe.