Mac System Data is huge: what to do

Apple does not break System Data down in System Settings. The common contributors are:

• App caches and logs.
• Developer files such as Xcode caches and iOS simulators.
• iPhone and iPad backups stored on the Mac.
• Time Machine local snapshots.
• Other files macOS cannot classify.

1. Open System Settings > General > Storage.
2. Read the System Data figure and the other categories.
3. Remove what you can from the categories above it, such as old files and apps you no longer use.
4. Restart the Mac. Some temporary files are cleared at startup, and the figure often drops after a restart.

Space Hogs checks the usual culprits behind a full disk: Xcode caches, iOS simulators, iPhone backups, app caches and old Downloads. You review each item and move it to the Trash.

1. Open Storage Explorer and choose Space Hogs.
2. Start the scan.
3. Review what it finds, including the size of each item.
4. Select what you no longer need and click Move to Trash, then empty the Trash.

• Caches rebuild as apps need them.
• Xcode DerivedData is rebuilt the next time you build a project, and unused simulators can be downloaded again from Xcode. Keep Archives you may need to symbolicate crash reports for released apps.
• Old iPhone backups are safe to remove if you have a newer backup or use iCloud Backup. Space Hogs shows the device name and last backup date.

• Give Storage Explorer Full Disk Access so protected folders are measured.
• Check the largest files view for forgotten disk images and videos.
• Items go to the Trash first, so you can put something back if you change your mind.