When you copy a file on APFS, it doesn't actually duplicate the file blocks, instead it just clones the metadata. This is known as copy on write (COW). That prevents identical files from using any more space until you make an edit to the duplicate file, and then , only the changed blocks take up space so substantially identical files share most of their storage in common even after a change.
I'm hoping there is some tool to find existing duplicates and replace them with clones, reclaiming the space used to store the duplicate.
Is there a way to use the copy-on-write cloning feature of APFS to reclaim space from existing duplicate files?