Mac System Data too large? How to clear it safely

System Data is everything macOS can't put in another storage category: caches, logs, swap files, temporary files, app support files and, on many Macs, Time Machine local snapshots and developer data. You can't delete it as one item. To shrink it, restart, find the largest folders, let old snapshots go, clear caches app by app and remove leftovers of apps you deleted. Some of it will always stay, because macOS and your apps use it.

Why Mac System Data gets over 100 GB

System Data is a leftover category: whatever is not an app, a document, a photo, mail or another listed type ends up there. That is why it can be huge on one Mac and small on another. The usual reasons for a very large number:

• Time Machine local snapshots. They hold changes since your last backup and can be large after big file changes. macOS frees them when it needs space.
• Developer data. Xcode build folders, simulator runtimes, Android emulators and the Docker disk image can each take tens of gigabytes.
• App caches. Browsers, messengers, music and video apps, and design tools keep large caches in your Library.
• Virtual machines. A Parallels, UTM or VMware disk stored in an app's data folder counts as one huge file.
• Leftovers. Data of apps you removed by dragging them to the Trash stays in your Library.
• Swap and temporary files. They grow while the Mac runs for days and often shrink after a restart.

The Storage view in System Settings also takes time to recalculate. After a cleanup, give it a few minutes before you judge the result.

Find what is large in System Data before deleting anything

Measure first. This Terminal command only reads folder sizes and deletes nothing. It lists the 15 largest folders in your Library:

du -hd 1 ~/Library 2>/dev/null | sort -h | tail -15

Run the same command on a folder from the result to go one level deeper, for example ~/Library/Caches or ~/Library/Containers. macOS may ask whether Terminal can access some folders; you can decline, and those folders are skipped. In Finder you can see the same sizes: open a folder in list view and turn on “Calculate all sizes” in the view options.

Write down what is big and which app it belongs to. Most folders are named after the app or its bundle identifier, such as com.spotify.client.

Restart the Mac before cleaning System Data

A restart is the cheapest step: it often recreates swap files and clears some temporary files. If System Data is still large, starting up in safe mode once clears some system caches, which macOS creates again as needed. Then restart normally and check again.

Time Machine local snapshots in System Data

If you use Time Machine, your Mac keeps local snapshots on the startup disk: about one an hour, each kept for 24 hours, plus one of your last successful backup. Apple says the Mac counts their space as available and removes them when it needs room, so they don't block downloads or installs. They can still make System Data look large.

To see them, run this. It only lists them:

tmutil listlocalsnapshotdates /

The simplest way to remove them is Apple's: switch Time Machine backups to manual in Time Machine settings, wait a few minutes until the snapshots are deleted, then switch automatic backups back on. Remember to switch them back.

To delete a single snapshot from Terminal, copy its date from the list above (for example 2026-10-20-093015) and run:

sudo tmutil deletelocalsnapshots 2026-10-20-093015

Replace the date with one from your own list. A deleted snapshot is gone for good: you can no longer restore files from that point if your backup disk is not connected.

Clear caches and logs app by app

Caches are meant to be rebuilt, so they are the safest thing to clear. Do it per app, not by emptying the whole Caches folder:

1. Quit the app whose cache is large.
2. In Finder, use Go to Folder and enter ~/Library/Caches.
3. Move only that app's folder to the Trash.
4. Open the app once. It recreates what it needs; the first start can be slower.

For Safari, Chrome, Firefox and other browsers, use the browser's own option to clear cached images and files. Many apps (Spotify, Slack, Teams, Discord) also have a setting to clear their cache, which is safer than deleting files.

Old logs live in ~/Library/Logs. They are usually small, but a crashing app can fill this folder. Remove old log files of a specific app there; leave the system logs in /Library/Logs and /private/var/log to macOS.

Remove leftovers of apps you already deleted

Dragging an app to the Trash leaves its data behind. Look for folders named after apps you no longer have in:

• ~/Library/Application Support
• ~/Library/Containers and ~/Library/Group Containers
• ~/Library/Caches

Only remove a folder when you are sure the app is gone and you don't need its data. Folders in Containers hold the documents and settings of sandboxed apps: deleting one of an installed app resets that app and can lose your files. If two apps come from the same developer, a shared folder may belong to the one you still use.

Xcode, simulators and Docker in System Data

If you write code, check ~/Library/Developer first: Xcode DerivedData, simulator devices, device support files and archives often take tens of gigabytes. Our guide Xcode taking up space on Mac explains which of these are rebuilt and which you should keep.

By default, Docker Desktop keeps all images, containers and volumes in one disk image inside ~/Library/Containers/com.docker.docker. Never delete that file by hand: clean up through Docker itself, which removes stopped containers, unused images and build cache.

What not to delete in Mac System Data

• System folders: /System, /private/var and anything you need administrator rights to remove. A cleanup guide that tells you to sudo rm -rf a system path is wrong.
• Swap files in /private/var/vm. macOS manages them.
• The Spotlight index. Deleting its folders by hand can break search. If you suspect it, let macOS rebuild it instead.
• Mail and Messages data (~/Library/Mail, ~/Library/Messages). Remove attachments inside the apps.
• Keychains and iCloud folders (~/Library/Keychains, ~/Library/Mobile Documents).
• Containers of installed apps, as above.

Before any manual cleanup, make sure you have a recent backup. Move files to the Trash instead of deleting them in Terminal, check that everything still works for a day, then empty the Trash: files in the Trash still take space until you do.

Where 1Cleaner for Mac helps with System Data

1Cleaner for Mac is a free cleaner that does the search part of this guide for you. It removes part of System Data: app caches, browser caches (locked while that browser is open), logs, temporary files untouched for days and leftovers of apps you already removed. It also lists iPhone and iPad backups and downloaded updates, installers, old downloads, large files and developer data such as Xcode, simulators and Docker. Its Storage view shows your disk by kind of data, then the folders and largest files behind each kind.

• Nothing is selected for you. Each item is labeled Safe, Ask AI or Risky, and Ask AI copies a ready question about it for any AI assistant.
• Files go to the Trash after a confirmation; simulators and Docker data are removed by their own tools after a separate warning.
• iCloud's and file-sync services' own data is never shown or removed.
• It leaves data that macOS and installed apps still use, so how much System Data shrinks depends on your Mac.
• Free, no ads, no account, no tracking. Scans run on your Mac; the app goes online only when you check for updates.
• Direct download (DMG), macOS 14 or later, Apple Silicon and Intel, signed with Developer ID and notarized by Apple.

Mac System Data: FAQ