Cassiel

Congratulations on so vehemently disagreeing with something I DIDN'T recommend. Read what I wrote. I didn't recommend MD5 specifically, what I said was you need to use a PROPER HASHING ALGARIM such as one from the MDx FAMILY or the SHA-x FAMILY, including (oh yeah) SHA-256. Additionally, I didn't mention anything about downloads. Stop making assumptions. Yes OBVIOUSLY if you are comparing File_A to File_B and they have different file sizes then OBVIOUSLY they are distinct and it's wasteful doing further 'checks' to confirm this FOR THIS SPECIFIC FILE_A TO FILE_B COMAPRISON. The subject of discussion was never how most efficiently to design the programmatic logic behind this process. The file name matching or not matching is COMPLETELY irrelevant. Again, it's not just as simple as the theoretical mathematics. Look.. at the end of the day it's becoming obvious you have very specific ideas about what a duplicate file finder in CCleaner *should* do and how it *should* meet your specific (I dare say very limited) needs. I don't know whether you are envisioning this as something to find duplicate *.dll libraries of something, but that's certainly not JUST what I would use it for. Nor does it appear anyone else here who has commented would use it in such a limited way.

I completely agree with Keatah and 4NTFan. As a long time fan of CCleaner I was excited to see this new feature added, but in its current implementation it's beyond useless. To have an even half way proper duplicate file finder, the mechanism for identifying such files MUST be some sort of hashing algorithm *as a minimum*. @Alan_B Regarding CRC32, this is simply not suitable. It's not an issue of mathematics, it's an issue of maliciousness (and fundamentally design). You need to use a proper hashing algorithm, such as MDx or SHA-x. I've seen on numerous occasions, through either malicious 'cleverness' or simply quirks of design, DISTINCT files that share the same CRC32 but clearly not the same MD5/SHA-1. They are different files. It's just these sorts of suspicious files you might want to verify. Not everything is purely hypothetical…. I'm sorry if I'm sounding overly critical/negative. I think having a (reliable) duplicate file finder built right into CCleaner is an excellent thing, but at the moment it just isn't. Not even close.