How To Clear System Data On Mac

Tips
1

My Mac’s storage is almost full and most of it is labeled as “System Data.” I’ve already deleted large files and apps, but the System Data section is still huge. I’m worried about deleting the wrong things and breaking macOS. Can someone explain safe ways to reduce System Data, what’s actually okay to remove, and what tools or steps you recommend?

2

System Data on macOS is a big junk drawer. You clean files, it stays huge. Here is what tends to work without breaking stuff.

  1. Check what is big first
  • Go to Apple menu > About This Mac > More Info > Storage Settings.
  • Look at Documents, Applications, iOS Files, etc.
  • Often backups, Xcode stuff, or VMs show up as System Data.
  1. Delete old iOS and iPadOS backups
  • Open Finder.
  • Plug in your iPhone or iPad once if needed.
  • In Finder sidebar, click your device.
  • Under Backups, hit Manage Backups.
  • Delete old device backups you no longer need.
    These often eat tens of GB.
  1. Clean Time Machine local snapshots
    These are “hidden” backups stored on the internal drive.
  • Open Terminal and run:
    tmutil listlocalsnapshots /
  • Then remove them with:
    sudo tmutil deletelocalsnapshots
    Repeat for each.
    If you do not use Time Machine at all, turn it off in System Settings first.
  1. Clear system and user caches
    This is safe.
  • In Finder, press Shift + Command + G.
  • Go to: ~/Library/Caches
  • Delete contents of the folders inside, not the Caches folder itself.
  • Then go to: /Library/Caches
  • Do the same.
    Reboot after.
  1. Remove old log files
  • Shift + Command + G.
  • Go to: /var/log
  • Delete old .log and .gz files.
    Do not touch folders you do not recognize.
    You can also use the Console app and clear reports there.
  1. Check large hidden stuff with a scanner
    Use a disk visualizer like GrandPerspective or DaisyDisk.
    Scan your whole disk.
    Sort by size.
    Look out for:
  • /Library/Application Support
  • ~/Library/Application Support
  • Old app data from Adobe, Steam, Xcode, Final Cut, etc.
    Remove app data for apps you no longer use.
  1. Delete old user account data
    If you had old user accounts, they often sit in /Users as big folders.
  • Go to System Settings > Users & Groups.
  • Remove unused accounts and choose to delete their home folders.
  1. Clean Mail downloads and attachments
    Mail stores local copies.
  • Open Mail.
  • In Mailbox menu, choose Erase Junk Mail.
  • Then Erase Deleted Items.
  • In Finder, Shift + Command + G, go to: ~/Library/Mail
    Sort by size and remove old mailboxes if you no longer need them, or at least clear Attachments subfolders.
  1. Clear browser data
    Safari:
  • Settings > Advanced > Show features for developers.
  • Then Settings > Privacy > Manage Website Data > Remove All.
    Chrome, Firefox, etc, clear cache in their own settings.
  1. Reduce iCloud Drive local copies
    If you use iCloud Drive Desktop & Documents
  • System Settings > Apple ID > iCloud > iCloud Drive > Options.
  • Enable Optimize Mac Storage.
    This pushes older files off local storage, so System Data and “Other Users” shrink over time.
  1. Rebuild Spotlight index
    Sometimes storage reporting bugs come from indexing.
  • System Settings > Siri & Spotlight.
  • Add your Macintosh HD to the Privacy list.
  • Remove it again.
    That forces a reindex and can fix wrong System Data size values.
  1. As a last resort, archive and reinstall
    If System Data stays huge and no folder explains it, something is corrupted.
    Quick but annoying fix that helped me once when System Data sat at 300 GB:
  • Back up to external drive with Time Machine or clone software.
  • Create a bootable macOS installer or use Recovery.
  • Erase only Macintosh HD, leave the separate Data volume if present, or better, back up and do a clean erase.
  • Reinstall macOS, then manually copy back files instead of restoring a full Time Machine system snapshot.
    That reset System Data to about 15 GB for me on Ventura.

General safety rule
If you do not know what a system file or folder is, do not delete it.
Target cache, logs, old backups, app support from uninstalled software, and obvious junk.
Take it step by step and check Storage after each group of changes so you see what worked.

3

System Data is basically macOS’s junk drawer plus everything it can’t be bothered to label properly. @jeff covered the “manual cleanup” angle really well, so I’ll skip repeating the cache/log/snapshot stuff and hit some other levers that actually change that bar without you poking around in /var hoping nothing explodes.

1. First, assume the Storage bar is lying (a bit)
System Data is often misreported. Before you start deleting like crazy:

  • Open Disk Utility
    • Select your internal drive
    • Check Used vs the sum of what “About This Mac > Storage” claims.
      If Used is, say, 300 GB but Storage says 420 GB in categories, it’s not that you actually have 420 GB worth of stuff. Spotlight / APFS accounting is just confused.

In that case, skipping straight to:

  • Safe mode boot
    • Shut down
    • Hold Shift while booting until you see the login
    • Log in, wait a bit, then restart normally

Safe mode cleans caches and forces a bunch of re-indexing. I’ve seen System Data drop tens of GB after a safe boot and normal restart, no manual deleting.

2. Virtualization & dev tools are sneaky System Data hogs

These very often land in System Data instead of “Apps”:

  • Docker Desktop

    • Open Docker > Settings > Resources > Disk image
    • Check the size, prune unused images & containers
    • On disk:
      • ~/Library/Containers/com.docker.docker
      • ~/Library/Group Containers/group.com.docker

  • Parallels / VMware / UTM

    • VM files can be 30–200 GB each
    • Usually live in ~/Parallels, ~/Documents/Virtual Machines, or similar
    • Move unused VMs to an external drive instead of deleting if you’re nervous

  • Xcode & simulators
    @jeff mentioned Xcode “stuff,” but you can go deeper without blindly wiping things:

    • In Terminal:
      • xcrun simctl delete unavailable
        Removes old device simulators
      • du -sh ~/Library/Developer
        See how big the Developer folder is
    • Xcode > Settings > Locations > Derived Data > click arrow and trash old projects

These three categories alone have “mysteriously” eaten 100+ GB and shown up as System Data for me.

3. Photos & iCloud weirdness

Photos libraries and iCloud caching often end up under “System Data” instead of “Photos” or “Documents,” especially if you’ve migrated systems a few times.

  • Check for multiple Photos libraries:

    • In Finder, search: kind:library photos
    • Look for big *.photoslibrary bundles
    • Right click > Show Package Contents is dangerous; instead:
      • Option key + open Photos
      • Choose which library is active
      • Trash old, unused libraries

  • iCloud Drive & System Data:

    • If Optimize Mac Storage has been toggled on/off a few times, your disk can accumulate local copies that don’t get properly re-accounted
    • Temporarily turn iCloud Drive off in System Settings > Apple ID > iCloud
    • Let it remove local copies (it will warn you first)
    • Turn it back on and re-enable Optimize
      It’s clunky, but I’ve seen that fix phantom “System Data” that was really stuck iCloud debris.

4. Old system snapshots & OS migrations

I’ll lightly disagree with @jeff on one point: manually deleting Time Machine local snapshots with tmutil deletelocalsnapshots is fine, but it’s a bit tedious and easy to miss the real culprit: APFS snapshots created by macOS updates and migration leftovers.

Try:

  • In Terminal:

    • diskutil apfs listSnapshots /
      If you see a ton of snapshots, those are taking real space
    • Delete non–Time Machine ones only if you know what they are
      If this list is long and you don’t care about rolling back, the more reliable “user-friendly” option is:

  • Create a fresh Time Machine backup

  • Then turn Time Machine off for a while

  • Reboot
    macOS tends to clear old snapshots fairly aggressively once there is an external backup and TM is disabled.

If you migrated from an older Mac:

  • Open Users folder in Finder
  • Check for Deleted Users or old home folders not hooked up to an active account
    Those entire home directories often sit in System Data.

5. Check for huge “orphans” the Storage view ignores

In addition to visualizers like DaisyDisk/GrandPerspective that @jeff mentioned, you can use plain Terminal to avoid installing tools:

  • sudo du -xhd 1 /
    Shows which top-level folders are actually big
  • Then drill down, for example:
    • sudo du -xhd 1 /System
    • sudo du -xhd 1 /Library
    • sudo du -xhd 1 /Users

You’re looking for something absurd, like:

  • /private/var/folders being 80+ GB
  • /private/var/tmp bloated with old installers
  • /Library/Application Support containing abandoned stuff from software you uninstalled ages ago

When you find a monster folder, google that exact path before deleting. Ten seconds of checking beats spending a weekend recovering.

6. Offload instead of delete when in doubt

If you’re scared to break things (which is reasonable):

  • Create a folder on an external drive: “Mac Cleanup Stash”
  • Instead of deleting suspect large folders, move them there first
  • Use the Mac for a few days
    • If nothing breaks, then delete from the external
    • If something does break, move it back

This is especially nice for:

  • Old app data in ~/Library/Application Support
  • Old project folders, libraries, or VMs

7. When System Data is >80–100 GB and nothing explains it

At that point, it’s often some combo of:

  • Corrupted APFS snapshots
  • Broken Spotlight / Storage indexing
  • Old OS cruft from upgrades over upgrades

You can spend hours chasing ghosts, or you can bite the bullet:

  • Backup important files manually to external drive (Docs, Desktop, Photos libraries, projects)
  • Boot to Recovery
  • Erase the internal drive
  • Fresh install macOS
  • Manually copy data back instead of restoring a full Time Machine system snapshot

I’ve seen System Data go from ~250 GB to ~20 GB instantly doing this, on a machine that survived 4 macOS upgrades.

Bottom line:
If you’re nervous about breaking stuff, prioritize:

  1. Safe mode + reboots
  2. Checking for huge VMs / Docker / Xcode / multiple Photos libraries
  3. Verifying with Disk Utility and du that the System Data size is even real
  4. Offloading suspicious big folders instead of deleting them directly

If all that still leaves “System Data” enormous and nothing on disk matches the number, that’s usually your sign to go for the clean reinstall rather than hunting phantom GBs forever.

4

Short version: before you start nuking hidden folders, focus on what changes “System Data” without you spelunking in /Library.

1. Stop trusting that “System Data” number blindly

I slightly disagree with @jeff on how much time to spend chasing that bar. It is often just wrong. If Disk Utility says you still have some free space and the Mac is usable, I’d avoid deep manual surgery and aim for big, safe levers first.

What I do instead of micro-cleaning caches:

  • Ignore the color breakdown in “About This Mac” and look only at the plain “Free / Used” in Disk Utility.
  • If “Used” roughly matches what du in /Users reports, you’re probably fine and dealing with a mislabeling issue more than actual bloat.

This matters because a ton of people panic at “300 GB System Data” when the disk only has 250 GB total used.

2. Purge content via the apps that own it

A lot of what shows as System Data is actually app content that macOS doesn’t categorize well. Instead of pruning in Finder:

  • Mail

    • Mail > Settings > Accounts > uncheck old accounts or turn off “Download Attachments” for huge IMAP mailboxes.
    • Mailbox > Rebuild on any mailbox that got enormous.
      This shrinks databases that otherwise look like “System.”

  • Music / TV / Podcasts

    • Check for downloaded episodes and offline content inside each app. Deleting from within the app fixes the accounting better than deleting the files manually.

  • Creative tools

    • Lightroom, Logic, Final Cut etc create giant caches and proxy media that often end up as System Data. Always use their internal “delete previews / proxies / cache” options instead of trashing their folders from Finder.

This is much safer than guessing which random Application Support folder is expendable.

3. Let macOS reclaim purgeable space

System Data often includes purgeable space that macOS will delete only under pressure. You can force its hand without low-level tinkering:

  1. Temporarily copy a large file (like a disk image) to your Mac until you are nearly out of space.
  2. Wait a bit. macOS will usually start purging hidden caches, old logs, and stale iCloud locals.
  3. Once you see free space bounce back, delete that dummy big file.

It is crude, but I have watched System Data drop a huge amount this way after the OS finally decides to clean house.

4. Prefer targeted uninstalls over random Library deletions

Instead of searching /Library and ~/Library for large folders and deleting by hand, use:

  • The original app’s uninstaller, if it has one.
  • Or reinstall the app, then immediately run its uninstaller.

This often removes drivers, background daemons, and support folders that macOS counts under System Data. Safer and cleaner than guesswork in /Library/Extensions or /Library/Application Support.

Example categories that benefit from a proper uninstall:

  • Old antivirus, VPN clients, printer suites
  • Audio plugins & drivers
  • “Helper” tools that live as menu bar items

5. Consider a non-destructive “reset” before a full wipe

I agree with @jeff that a clean install is the nuclear fix, but before you go that far:

  • Create a current Time Machine backup.
  • Boot to Recovery, then run the macOS installer over your existing system without erasing the disk.

This effectively refreshes system components and sometimes dumps stale snapshots or migration leftovers that were living as System Data, but it keeps your user data in place. It is not as thorough as a wipe, yet a lot less hassle.

If that still leaves a ridiculous System Data number that does not match disk usage, then consider the full erase + manual restore route.

6. “How To Clear System Data On Mac” without breaking anything

Putting it together, a cautious order that avoids risky deletions:

  1. Check Disk Utility’s Used/Free vs the Storage bar.
  2. Boot once in Safe Mode like @jeff suggested, then back to normal.
  3. Inside major apps (Mail, Photos, Music, creative tools), clear caches / previews / downloads using their own options.
  4. Let macOS reclaim purgeable space by briefly filling the disk with a dummy large file, then removing it.
  5. Reinstall & properly uninstall heavy old apps instead of manually cutting their Library folders.
  6. If still stuck, run a non-destructive macOS reinstall from Recovery.
  7. Only if nothing lines up and System Data is still absurd, do a full erase and restore only your personal data.

This keeps your risk of breaking the OS low while still giving that “System Data” bar real pressure to shrink, instead of hunting random folders under /var and hoping for the best.