Install it
Download the disk image, drag DiskDuo to Applications and open it. The app is signed with a Developer ID and notarized by Apple, so macOS checks it with Apple before it opens for the first time.
One build runs natively on Apple silicon and Intel. macOS 14 Sonoma or later is required.
The first run
DiskDuo asks for nothing on launch. Three screens explain what it does, offer Full Disk Access, and then let you scan your home folder or the whole Mac.
Full Disk Access is optional. Without it DiskDuo still scans and still cleans; some folders macOS keeps private are missing from the total, and the app says so rather than quietly under-reporting.
What you see after a scan
Home summarises what can be cleared and what is free. Explore draws the scan as a treemap, with eight other readings a click away. The sidebar keeps the disk ring, the current folder and the easy wins; the inspector on the right describes whatever is selected.
Open DiskDuo again later and it shows the figures from that scan with the date they were taken, so there is never an empty screen. Scan again to bring them up to date.