Source: https://mactoolbox.app/mac-system-data-storage-huge

# Mac System Data is huge: what to do

By Nikhil Barik · Published November 3, 2026

## Quick answer

System Data is space macOS cannot put in another category. It is often caches, developer files, iPhone backups and Time Machine local snapshots. Find the big ones with Space Hogs in Storage Explorer, review them and move what you do not need to the Trash.

## What System Data contains

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.

## The built-in way

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.

## The Toolbox way: Space Hogs in Storage Explorer

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.

## Is it safe to delete?

- 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.

## Tips and troubleshooting

- 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.

## Frequently asked questions

**What is System Data on Mac and how do I clear it?**

It is space macOS cannot put in another category, often caches, developer files, iPhone backups and Time Machine local snapshots. Space Hogs finds the common ones so you can review and move them to the Trash.

**Is it safe to delete Xcode DerivedData and simulators?**

Yes. DerivedData is rebuilt on your next build, and unused simulators can be downloaded again. Keep Archives you may need for crash reports.

**Will I lose data if I delete caches?**

Caches rebuild as apps need them. Apps may be slower the first time you use them afterward.

**Why is the figure different from what Toolbox shows?**

Without Full Disk Access, some protected folders cannot be measured, so Storage Explorer's totals can look smaller than what macOS reports.

## Tools mentioned

- [**Storage Explorer**: See what’s filling your disk, find the usual space hogs and clear them out safely.](https://mactoolbox.app/free-up-storage-mac)
- [**Find Duplicates**: Find identical files across folders and move the extras to the Trash.](https://mactoolbox.app/find-duplicate-files-mac)
- [**Uninstall App**: Remove an app together with the caches, preferences and data it leaves behind.](https://mactoolbox.app/uninstall-apps-mac)

## Keep reading

- [Storage Explorer](https://mactoolbox.app/free-up-storage-mac)
- [Find Duplicates](https://mactoolbox.app/find-duplicate-files-mac)
- [All guides](https://mactoolbox.app/guides)