When I learn new program, I like learning manual first. So I found the manual on the page :
https://www.cisdem.com/manual/duplicatefinder.pdf . It takes me some time to find out the manual for the author keep it so secret.
Download and install it. when I see the icon on my mac's interface, it shows me I have installed
DuplicateFinder on my Mac. The DuplicateFinder's interface is very simple - only three button : " + ", "Scanner", "Setting". I can click "+" to add the files and I also can drag and drop to add the files. For the "Setting", there are "General" and "Filthers" two buttons. After all the done, I click "Scanner" button. When it star scanning, it shows me "Files Scanned" "Duplicates Found" "** GB Found". I think this is great for me. After scanned, my Duplicates also shocked me. There are too many duplicates take my mac's space - almost 1GB. I check the duplicates and find it collect the same duplicate together, though the files name is different. I delete all the duplicate the files. Now my mac is faster than before.
Good to try.