LighterMac opens the grey “System Data” bar in your Mac's storage settings and names what's inside: caches, build folders, old iPhone backups, app leftovers. Each item says what happens if it goes, and only things that rebuild themselves are ever suggested. Everything goes to the Trash first, with a list to put it back. It also uninstalls apps with their leftovers and moves rarely used files to another drive. Your files never leave your Mac.