Signatures from each of your files are compared to determine which files are identical, regardless of what directory or filename and extension they have. Format : Mac OS Extended (Case-sensitive, Journaled) then it. Select the folders you would like to scan, press process and watch the duplicates get identified. This happens when the file system you are trying to copy the files to does not understand upper/lower-case file names. This is low hanging fruit for Scooter, in that you already have a lot of the code that would be needed. This app will help you identify which files you should clean up. Scooter already has a lot of the base functionality that would be needed, in that it runs and displays the directory structure and files, and does compares (and the CRC compare type would be a good means of identifying name changes), and has various filters. dupeGure is free and multiplatform, and has some of the basics right, but does not do file-id exclusions properly, and its compares are a lot cruder than BC has. Duplicate Detective and Gemini 2 are probably the things that come closest (they run on a Mac), but they are in terms of scanning capability pretty slow and have problems with bigger drives and NAS. But sometimes, you have to run down where you have file duplicates, and I very much need something like BC with all its filter features, and so far at least, I have not been able to find anything. Do not get me wrong, I am happy with Beyond Compare, it has been over the years the best investment in utility software I have ever made (especially when BC4 added Mac support, as I run on Windows, Linux, and macOS), the free (KDiff3, Meld, etc.) and paid alternatives really not even close on speed, options, functions, filters, and so forth. selecting My Music and then from menu View > Show Duplicate Items or if you press Alt/Option key Show Duplicate Items will change to Show Exact Duplicate.

I would be happy to see a Duplicate finder type capability added to Beyond Compare (or as a separate product, based on BC code).

Mac find duplicate files in directory