> So would some form of CRC. Less tooling directly supports them though. The Windows Explorer extension I use does, but others just support MD5 and maybe some

> So would some form of CRC. Less tooling directly supports them though. The Windows Explorer extension I use does, but others just support MD5 and maybe some SHA variants, similarly for download management browser extensions. And for this use people are just familiar with MD5. You'd be surprised how many in tech fields who don't touch encryption much, are relatively unaware of changes from the last decade or two. Even long-time command-line dwellers might have to lookup how to check a CRC despite cksum being part of the same package as md5sum/sha1sum/et.al. and installed by default practically everywhere unix-a-like just because they've always used stronger hashes for that. > The length extension problems with SHA256 are not relevant to this use case. No, but “by default” I meant in the general case. Being in the habit of using a choice that is better generally and no worse specifically, is safer than using good enough in one place and hoping you remember to vary when there are different concerns. My memory is somewhat random, so I prefer to err on the side of caution when trying to develop habits! > but I think it's simpler to just avoid relying on MD5 to prove that 2 flies are likely the same in general Agreed, and I do. Though I'd not go as far as to chastise those using md5 where it is still sufficient.