How to Clear System Data Storage on Mac

What is "System Data" on Mac?

System Data (called "Other" on older versions of macOS) is the bucket in your Mac's storage chart for everything macOS cannot sort into a named category like Apps, Photos, Documents, or Music. It is not one folder you can open — it is a running total of app caches, system and app logs, temporary files, virtual-memory swap files, Time Machine local snapshots, old device backups, browser data, and developer files scattered across your disk.

Because it is a catch-all, System Data behaves differently from other categories: it grows quietly in the background as apps cache data, builds pile up, and logs accumulate, and macOS never shows you an itemized list of what is inside. That is why it routinely reaches 30, 50, or even 100+ GB on Macs used for work or development, and why it feels impossible to shrink from the Storage screen alone.

The good news is that most of what lives in System Data is regenerable. Caches get rebuilt the next time an app needs them, swap files are managed automatically by macOS, and local Time Machine snapshots are thinned out by the system when disk space runs low. The parts worth clearing manually are the ones macOS never touches on its own: stale app caches, old logs, forgotten iOS device backups, and developer build artifacts.

Check what's inside System Data

Start by measuring the problem. On current versions of macOS, the storage overview lives in System Settings rather than the old About This Mac window, and it takes a minute to calculate after you open it.

The Storage screen only tells you the total, so the next step is to look inside the folders that feed System Data. The three biggest contributors on most Macs are user caches, system-wide caches, and logs — all of which you can inspect directly in Finder.

1. Open System Settings from the Apple menu, click General in the sidebar, then click Storage. Wait for the colored bar to finish calculating, then hover over the segments — System Data is usually the light gray segment near the end of the bar.
2. In Finder, press Command-Shift-G to open Go to Folder, type ~/Library/Caches and press Return. This is where apps running under your user account store their cache files.
3. Repeat with /Library/Caches (no tilde) to see system-wide caches shared by all users, and ~/Library/Logs to see the log files apps have written over time.
4. In each folder, choose View > As List, then click the Size column to sort largest first. If sizes show as "--", press Command-J and enable "Calculate all sizes". Note which folders are taking multiple gigabytes — those are your targets.

If the Size column stays empty for some folders, that is normal — Finder needs permission and time to calculate folder sizes. Sorting by size in list view with "Calculate all sizes" enabled gives you the clearest picture.

Clear caches and logs safely

Caches exist to make apps faster, so deleting them is safe by design: an app that finds its cache missing simply rebuilds it. The trade-off is that the first launch after clearing may be slightly slower while the cache repopulates. Logs are even lower risk — they are diagnostic text files you will almost never need unless you are troubleshooting a specific problem.

The one rule that matters: delete the contents of a cache folder, not the folder itself, and always quit the app first. An app writing to its cache while you delete it can end up in a confused state, and some apps expect their named cache folder to exist even when empty.

1. Quit every app whose cache you plan to clear — use Command-Q, not just closing the window. For browser caches, it is easier to use the browser's own clear-data feature instead.
2. In Finder, go to ~/Library/Caches, open one of the large folders you identified earlier, select its contents with Command-A, and move them to the Trash with Command-Delete.
3. Work through the largest folders one at a time rather than deleting everything at once — if an app misbehaves afterward, you will know exactly which cache was responsible.
4. Do the same in ~/Library/Logs for any log folders taking real space. Old .log files and crash reports can be trashed without consequence.
5. Empty the Trash when you are done — until you do, the files still count against your disk, and the System Data number will not move.

Avoid deleting anything inside /System or /private unless you know exactly what it is. macOS manages those areas itself, and the space they use is not worth the risk of guessing.

Remove developer junk (Xcode, simulators, package caches)

If you have ever installed Xcode, developer files are almost certainly the single biggest slice of your System Data. Xcode stores build products and indexes in ~/Library/Developer/Xcode/DerivedData, a folder that commonly grows to 20-50 GB and is completely safe to delete — Xcode rebuilds it on the next build.

Simulators are the other heavyweight. Each iOS simulator runtime you have ever downloaded can occupy 5-8 GB under ~/Library/Developer/CoreSimulator, and old runtimes stick around long after you stop targeting those iOS versions. Running xcrun simctl delete unavailable in Terminal removes simulators whose runtimes are no longer installed.

Package managers pile on too: npm, CocoaPods, Swift Package Manager, Homebrew, pip, and cargo each keep their own download caches, and together they often account for another 5-15 GB. We cover every one of these — with exact paths, commands, and what is safe to remove — in our dedicated guide, "Delete Xcode DerivedData & Developer Caches Safely".

Delete old iOS backups and large files

Local iPhone and iPad backups are a classic System Data surprise: a single device backup can be 5-20 GB, and if you have backed up more than one device — or an old phone you no longer own — the copies just sit there forever. macOS stores them in ~/Library/Application Support/MobileSync/Backup, but do not delete them from Finder by hand; use the built-in manager so the backup index stays consistent.

To review backups, connect a device (or just open a Finder window), select the device in Finder's sidebar, and click Manage Backups. You will see every stored backup with its date — delete any backup for a device you no longer have, or any backup older than one you have since made in iCloud.

Beyond backups, sweep for large files you have simply forgotten about. Sort your Downloads folder by size and clear old installers and disk images (.dmg, .pkg, .zip files are pure dead weight once installed). The Storage screen in System Settings also offers built-in recommendations — Store in iCloud, Optimize Storage, and Empty Trash Automatically — which Apple documents in its storage support guide.

When to use a cleanup tool

Manual cleanup works, but it has two honest costs: it takes an hour of poking through Library folders, and you are the one deciding whether each mysterious multi-gigabyte folder is safe to remove. If you would rather not make those calls blind, a cleanup tool that explains what it finds is the sensible middle ground.

AskClean was built for exactly this problem. One scan maps your disk into 12 categories — system caches and logs, browser caches, Xcode DerivedData, old simulator runtimes, AI model caches, package-manager caches, app leftovers, large downloads, and more — and its AI explains each item before you delete: what it is, whether it can be rebuilt, and what deleting would cost you.

Its safety model matches the advice in this guide: every deletion goes to the Trash so you can restore anything, nothing runs until you confirm each item yourself, and your documents, photo library, and system files are never touched. Since version 3.3 it also cleans your Photos library — duplicates, blurry shots, and oversized videos — with all analysis on-device.

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