Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

When I did this recently I used Lexicon DJ management (as I'm a DJ and it has lots of other features I was using too).

There are a few options to choose from in terms of how it searches and how strict it is when trying to find duplicates. I'm not sure which features are available on the free version, I paid just for one month to sort out a lot of things within my DJ library but it may be worth looking in to to see if it can serve your needs :)

edit to add more info

Website says - "With Find Duplicates you can scan all your tracks in your library and automatically compare them based on the audio signature or tags. This way truly identical audio duplicates are found. This even works with different file types. If you have an MP3 and a WAV with the same audio, Lexicon will match them and lets you choose which one you want to keep."

So it doesnt just scan filenames it compares the audio files themselves to weed out duplicates.

Here is a YT video of the process from their site