Although the system should not take up much disk space, there are cases when it usurps almost all of it. It may be that some files (for example, your music or photos) are recognized as system related or that the stats you see are simply wrong. There are also situations when space taken by the System increases drastically in a few days without a user’s active participation. The causes of such an issue may vary. To isolate your problem, try the following strategy.
Rebuilding the Spotlight
It may be that the storage reporter fails to display data properly.
- Find System Preferences in the Apple menu, and then click Spotlight.
- Choose the Privacy tab.
- Add a hard drive for reindexing to the list of locations that Spotlight is prevented from searching by dragging it there or clicking the Add
- Find it in the same list and click the Remove
- Quit System Preferences to let Spotlight reindex the contents of your disk.
- Alternatively, you can use the following command in Terminal: sudo mdutil -E /
It will take some time, so do not be disappointed if new stats do not show up immediately.
If you get the same results, click on the HD icon on the desktop. Then go to the File menu and choose Get Info. There you can see how much space is available. If “Available” is really low, try deleting or transferring some files to the iCloud. Before doing that, make sure you have all of them copied and stored somewhere else. If nothing changes, proceed with the next steps.
Since booting in Safe Mode makes the system remove all cache files that take up a significant amount of space after some time (up to 100GB), this might help you regain your space back.
To boot a computer in Safe Mode:
- Turn your Mac off, and then press a power button and the Shift Hold the latter until you see a login screen.
- Restart your Mac in a normal mode and check the stats again.
First Aid Disk Utility
The System eating up too much space may indicate problems with a hard drive. Run First Aid Disk Utility to see if your disk is corrupted. To access First Aid Disk Utility:
- Click on the Spotlight icon from the menu bar and type Disk Utility.
- Double-click on the displayed search result. When Disk Utility opens, choose the First Aid tab.
- Alternatively, you can find it via Finder. Open it and choose Scroll to the bottom of the window to find Disk Utilities.
Disabling Time Machine
Time Machine is a built-in tool. By default, it also stores a local backup that is shown as system/purgable. To find out how much space is used by TM, click the Apple icon on the menu bar, choose About This Mac, and then select Storage. The Backups category shows your local backups. To stop TM from creating them and make it delete existing ones, use a Terminal command. Press Command+Space and type Terminal. Open it and enter sudo tmutil disablelocal. You can easily re-enable it with sudo tmutil enablelocal.
If nothing mentioned below seems to help, contact Apple support.