There are different ways to end up with duplicate files on a Mac. To save on drive space, you may wish to delete them. Before you can delete them, you need to find them! There is no built-in way to do that on a Mac. So, most people use a third-party App to do the finding and then delete the files manually. This article lists some third-party duplicate finding Apps (I use Gemini 2) and how to delete the duplicates.