If you have opened System Settings > General > Storage on your Mac lately and felt a mild panic at the size of the “System Data” category, you are not alone. It is routinely the biggest item on the list, and it is also the least transparent. This guide explains what is actually in there, what you can safely delete, and how to free up meaningful space without breaking anything.
What counts as “System Data”?
Apple groups several things under this label:
- Cache files from apps and the OS
- Log files generated by the system and apps
- Temporary files that should delete themselves but sometimes do not
- Virtual memory swap files (used when RAM is under pressure)
- Time Machine local snapshots (if you use Time Machine)
- Fonts, language packs, and other system assets
The frustrating truth is that macOS does not give you a fine-grained breakdown. “System Data” is a catch-all.
TL;DR: the quick wins
If you just want to reclaim space without reading the whole guide, here are the three things that actually move the needle:
- Delete local Time Machine snapshots (can be several gigabytes)
- Clear app caches (especially Xcode, Spotify, and your browser)
- Empty the Trash (obvious, but often forgotten)
Step 1: Check Time Machine local snapshots
Time Machine creates hourly local snapshots even when your external drive is not connected. These are useful, but they can add up fast.
To see what you have, open Terminal and run:
tmutil listlocalsnapshots /You will see a list of snapshots with timestamps. macOS is supposed to delete these automatically when storage gets tight, but you can delete them manually:
tmutil deletelocalsnapshots [date-time-string]Replace the placeholder with the timestamp you see in the list, for example 2025-06-01-143022.
Step 2: Clear browser cache
Browsers accumulate cache quietly. In Safari, go to Safari > Settings > Advanced, enable the Develop menu, then choose Develop > Empty Caches. In Chrome, open Settings > Privacy and security > Clear browsing data, select “Cached images and files”, and click Clear.
Step 3: Clear app caches
App caches live in ~/Library/Caches. You can open this folder by holding Option and clicking the Go menu in Finder, then selecting Library. Look for large folders from apps you recognize and delete their contents (not the folders themselves, just the files inside).
Common offenders: Spotify stores downloaded music here if you have streaming quality set high. Xcode caches derived data that can run to tens of gigabytes.
Step 4: Remove Xcode derived data (if you use Xcode)
Xcodes derived data folder can grow to 20–30 GB without you noticing. Open Xcode, go to Settings > Locations, and click the arrow next to the Derived Data path. In Finder, select everything inside and delete it. Xcode will rebuild it the next time you compile.
Step 5: Check for large log files
System and app logs live in ~/Library/Logs and /Library/Logs. They are usually small, but occasionally an app misbehaves and writes enormous log files. Sort by size in Finders list view to spot them.
What you should not delete
Avoid deleting anything in /System or /Library at the root level. Do not delete swap files manually. Do not use cleaning apps that promise to “safely remove system files” — they often remove things that look unused but are not.
The honest answer about “System Data”
Apple does not expose a detailed breakdown of System Data by design. Some of it — like swap files and local snapshots — will shrink on its own as macOS manages resources. The things you can control are caches and logs. After clearing those, if System Data is still large, it is likely swap or snapshots that will resolve themselves once the Mac has breathing room.
The most reliable way to free up space is to focus on what you can actually see: large files in Downloads, videos in Desktop, unused applications. Those tend to account for far more space than System Data does.