Mac "System Data" taking too much space: how to clean it safely

What is System Data?

System Data, called "Other" on older versions of macOS, is a catch-all category. It covers files that are not apps, documents, photos, music or other media. Some of it you need, and some is clutter that should have been cleared long ago.

How to check how much space System Data uses

1. Click the Apple menu in the top-left corner.
2. Open System Settings › General › Storage. On older macOS versions the path is System Preferences › Storage.
3. Wait for the bar to finish calculating. It can take a minute.
4. Find System Data in the bar. It is usually shown in grey.

Write the number down so you can compare after cleaning. There is no single correct size. What matters is whether it keeps growing and whether you are running out of room.

Start with the built-in storage recommendations

The Storage screen lists recommendations that are safe to use and take seconds.

• Store in iCloud keeps only recent files on the Mac and moves older ones to iCloud, if you have the iCloud storage for it.
• Optimize Storage removes films and TV shows you have already watched in the Apple TV app.
• Empty Trash Automatically deletes items that have been in the Trash for 30 days.
• Reduce Clutter shows large files. Click Review Files and work down the list.

These usually free a few gigabytes. Large System Data figures need the steps below.

How to delete Time Machine local snapshots

Local snapshots are often the largest single item. Time Machine creates them on the internal drive while your backup drive is not connected, and they can add up quickly.

1. Open Terminal from Applications › Utilities.
2. Run tmutil listlocalsnapshots /. A list of dates means you have snapshots.
3. To delete all of them, run sudo tmutil deletelocalsnapshots / and enter your administrator password.
4. To delete one, pass its date instead, for example tmutil deletelocalsnapshots 2024-11-26-103045.

The backups on your external Time Machine drive are not touched. You lose only the local safety copies, which is fine if you back up to a drive regularly or do not use Time Machine.

How to remove old iPhone and iPad backups

Every backup you make to the Mac lives in System Data, and each one can be large. The easiest way to see them is in Finder:

1. Connect your iPhone or iPad and select it in the Finder sidebar.
2. In the General tab, click Manage Backups.
3. Look at the device names and dates, and delete the ones you no longer need.

The backups are stored in ~/Library/Application Support/MobileSync/Backup/. The folder names are long strings that do not say which device they belong to, so use Manage Backups rather than guessing.

Before deleting anything, make sure you have a recent iCloud backup or a newer computer backup. If you are testing the iOS 27 beta, keep the archived backup you made before installing it. A backup made on a beta cannot be restored onto an older iOS version, so that archived copy is what you restore after downgrading from the iOS 27 beta to iOS 26. Archived backups show the date beside the device name in Manage Backups. Our guide to backing up before the iOS 27 beta explains how to archive one.

How to clear app and browser caches

Apps keep caches so they load faster, and browsers and creative apps can build up large ones. Apps recreate the caches they need, so clearing them is safe.

Safari

1. Open Safari › Settings › Advanced.
2. Turn on Show features for web developers.
3. Choose Develop › Empty Caches from the menu bar.

To remove stored site data as well, go to Safari › Settings › Privacy, click Manage Website Data and then Remove All. This signs you out of websites.

Chrome

1. Open Clear Browsing Data from the Chrome menu.
2. Set the time range to All time.
3. Tick Cached images and files and click Clear data.

Other apps

1. In Finder, press Command + Shift + G.
2. Go to ~/Library/Caches.
3. Open the folders for apps you use heavily and delete their contents. Leave the folders themselves in place.

Creative suites, team chat apps and music streaming apps are common sources of large caches. Quit an app before clearing its cache.

How to clear old logs and diagnostic reports

macOS and apps keep logs that accumulate over months. They are rarely large, but they are easy to clear.

• In Finder, use Command + Shift + G to open ~/Library/Logs and /Library/Logs, and delete old log files. Keep anything from the last few days.
• Open ~/Library/Logs/DiagnosticReports and delete its contents. These reports are only useful if you are troubleshooting a problem with Apple Support.

How to remove leftover macOS installers and updates

Installers and update files sometimes stay behind after an update.

• Open the Applications folder and look for any app named Install macOS followed by a version name. Drag it to the Trash. You do not need it after updating.
• Check /Library/Updates and ~/Library/Updates, if they exist, and delete their contents.
• Check the Downloads folder too. Sort by size and remove old disk images, installers and archives. Downloaded IPSW firmware files for an iPhone or iPad are large and can go once the restore is done.

If you are installing the macOS 27 beta, our macOS 27 beta installation guide explains how much free space to leave before you start.

Clearing Xcode data if you are a developer

Xcode can account for a large share of System Data.

• Delete the contents of ~/Library/Developer/Xcode/DerivedData. Xcode rebuilds what it needs.
• Run xcrun simctl delete unavailable in Terminal to remove simulators for runtimes that are no longer installed.

Mail attachments

Apple Mail stores downloaded attachments on the Mac, and years of email can add up. Deleting old messages with large attachments, or removing attachments from messages you keep, reduces it. Avoid deleting Mail's internal index files by hand; Mail has to rebuild them, which takes a long time on a large mailbox.

Empty the Trash and restart

Files in the Trash still count against your storage. Control-click the Trash in the Dock and choose Empty Trash. Then choose Apple menu › Restart. macOS does not always recalculate storage straight away, and a restart forces it to. Open System Settings › General › Storage again and compare with the number you noted at the start.

What not to delete

• The /System folder. It holds core macOS files.
• Anything in /usr or /bin.
• Folders in /Library/Application Support unless you know exactly which app they belong to.
• Files ending in .plist. They are preferences, and deleting them resets the app's settings.
• System log folders such as /var/log. The gain is small and the risk is not worth it.

Stick to caches, logs, backups, snapshots and installers. Deleting system folders to win back space can leave you reinstalling macOS.

Using a cleanup app instead

If you would rather not use Terminal, third-party tools can do much of this for you. CleanMyMac automates cleanup of caches, logs, old backups and snapshots. DaisyDisk and OmniDiskSweeper show what is using space so you can decide what to remove. Whatever you use, check what it plans to delete before confirming, especially device backups.

When System Data stays large

If System Data is still large after every step above, look for a single app creating huge files; a disk visualiser makes that obvious. Reinstalling macOS keeps your files but replaces the system, and Apple Support can help if neither works. Before reinstalling, make a full Time Machine backup.

How to keep System Data under control

• Monthly: clear browser caches, empty the Trash and tidy the Downloads folder.
• Backups: back up your iPhone to iCloud, or delete older Mac backups after each new one.
• Time Machine: connect the backup drive regularly so local snapshots do not pile up.
• Updates: remove macOS installers once you have updated.

What to do next

If your iPhone is short of space as well, the same approach works there: our guide to cleaning up iPhone storage covers the iPhone equivalent of System Data. And if you are freeing space on the Mac to install a beta, check that your model is on the macOS 27 supported Macs list first.

Frequently asked questions