Your first scan
What to expect the first time you open DiskPeek.
Pick something to scan
The welcome screen gives you two ways in. Scan a Folder opens a picker so you can point at anything you like, and the second button scans your startup disk. Both end up in the same place.
Your volumes are also listed in the sidebar, and once you have scanned something it turns up under Recent locations so the second visit is one click.
macOS will ask permission first
The first time you scan a volume, DiskPeek explains what is about to happen and then macOS shows you a folder chooser. Pick the highlighted item and the scan starts.
This only happens once per location. See why macOS asks for the full explanation.
You do not have to wait for it to finish
Results appear as they are found. Start clicking into folders straight away and the sizes keep climbing underneath you as more of the disk is counted. The bar along the bottom shows how far along it is, how fast it is going, and how much is left.