My Mac mini was telling me I had over 80GB of "System Data" to free up. CleanMyMac wanted €34/year. DaisyDisk wanted €10 just to tell me where the files were. So I spent an evening writing a bash script instead. The problem with "System Data" on macOS If you've ever opened System Settings → General → Storage and seen a huge "System Data" slice, you know the feeling. macOS is notoriously vague about what's in there. The real culprits are usually: Time Machine local snapshots — macOS keeps these silently on your SSD, often tens of GB Xcode DerivedData and archives — rebuilds from old projects you haven't touched in months Game data from titles you uninstalled ages ago iMazing or other backup apps storing full iPhone backups locally App caches that grow indefinitely and are never cleaned automatically None of these show up clearly in Finder. You need to know where to look.…