Few things are more frustrating for Mac users than opening System Settings > General > Storage only to discover that mysterious "System Data" (formerly "Other") is consuming 80GB, 120GB, or even half of their total internal solid-state drive (SSD). Because macOS does not provide a direct one-click button to purge this category, many users mistakenly download risky third-party utility software that degrades system performance.

1. What Actually Lives Inside 'System Data'?

macOS groups any file that does not strictly fit categories like Applications, Documents, Music, or Photos into System Data. The most common space hogs include:

  • APFS Local Snapshots: Time Machine backup points generated automatically on your local drive when your external backup drive is unplugged.
  • Application Caches & Logs: Residue generated by web browsers, video editing suites, and messaging platforms located in ~/Library/Caches.
  • Orphaned iOS/iPadOS Backups: Old device full backups preserved when updating your iPhone via Finder or iTunes.
  • Xcode Derived Data: If you or your developer tools ever compiled software, gigabytes of intermediate build artifacts linger quietly.

2. Method 1: Thin APFS Local Snapshots via Terminal

The fastest way to recover 20GB to 50GB in seconds is thinning unneeded Time Machine local snapshots. Open Terminal and run the following read-only command to see what exists:

tmutil listlocalsnapshots /

If you see multiple dates listed, execute the built-in system thinning command to reclaim space:

tmutil thinlocalsnapshots / 10000000000 4

This prompts macOS to immediately prune and purge local temporary snapshots while keeping your core system files untouched.

💡 Clean User Cache Remnants Manually In Finder, press Cmd + Shift + G, enter ~/Library/Caches, and press Enter. You can safely inspect large folders belonging to software you no longer use or browsers holding gigabytes of stale media caches and move them to Trash.

3. Method 2: Purge Legacy Mobile Device Backups

Old iPhone backups are often completely forgotten. To review them natively:

  1. Go to System Settings > General > Storage.
  2. Scroll down to iOS Files and click the Info (ℹ️) button.
  3. Select outdated device backups from previous years and click Delete.