I am just wondering is there any way to find out duplicate files in my Mac? Because when I download something from "torrent", some unnecessary file also download besides the main file with `.dat` extension. I want to delete all of these `.dat` extension files at a time. Because it's a lot of in numbers & store in many different directories. If I want to find them one by one I have to do a lot of works. Is there any free apps to do that job or some way I can find & delete them?