What to do if Mac says disk is full?

Hi, yes macOS has built-in tools that make this pretty easy. First go to Apple Menu > System Settings > General > Storage, there you’ll see a breakdown of what’s using space (Apps, Documents, System Data, etc.). It also gives you recommendations like “Optimize Storage” and “Empty Trash Automatically”.

Usually the safest quick wins are removing large unused apps, clearing Downloads folder, and checking for large files in Documents or Movies. You can also enable iCloud Drive optimization if you use iCloud, which moves older files off your local disk.

If “System Data” is unusually large, a simple restart and clearing Time Machine local snapshots (if enabled) can sometimes help.

Just avoid deleting system folders manually—stick to the Storage recommendations and you should be fine.