Duplicate File Finder

[AceInfinity]

What I am trying to ask is:
Why does it search for similar file sizes when, if two file sizes are not the exact same size, it can't be the same file?

Answer: To narrow the search.

For example if you have files in a directory as the following:
-File1 (10GB)
-File2 (11GB)
-File3 (3.05Kb)
-File4 (3.21Kb)
-File5 (3.25Kb)
-File6 (3.35Kb)
-File7 (3.05Kb)

If you're comparing for similar MD5 hashes, to compare File5 to all files including File1 and File2 would be senseless because obviously they aren't going to be the same file, they have GB's more data than the file in comparison itself. So if you were to compare File5 to File3 through to File7, then that would speed things up because you're not comparing the file to every other file to check for the same MD5 hash, but only a select few now.