Recent versions of MacOS with AFS can do this to some extent: At the time you make a copy of a file with the Finder, MacOS makes a COW (copy-on-write) copy of t

Recent versions of MacOS with AFS can do this to some extent: At the time you make a copy of a file with the Finder, MacOS makes a COW (copy-on-write) copy of the file which behaves like a hardlink until you modify one of the copies, at which point the modified one becomes a separate file with its own identity. But AFAIK MacOS doesn't attempt to proactively dedupe the file system.