Disk Doctor is to Disk First Aid what BBEdit is to SimpleText. It will find problems with your disks that you didn’t even know were problems (more on this later). Sure, Disk First Aid (DFA) can fix minor errors with a missing custom icon here and there, but Disk Doctor can find and fix much more. Everything from bad b-trees to bad file modification dates fall under Disk Doctor’s “I Can Fix This” list, and that’s impressive.