> SHA-2, SHA-3, BLAKE2b, Skein, Whirlpool, etc.: We don't have any collisions for these, so it doesn't get any better than that. There are important difference

> SHA-2, SHA-3, BLAKE2b, Skein, Whirlpool, etc.: We don't have any collisions for these, so it doesn't get any better than that. There are important differences; some of those primitives are definitely more trustworthy than others. SHA-2 and Whirlpool use the old Merkle–Damgård construction, which has fallen out of favor because of unfortunate properties. They are vulnerable to length extension attacks, such that it can be misused. For instance, if you want to use it as a keyed hash, you cannot just do sha2(key + message) (where + is concatenation). You have to use something like HMAC for that. Skein is much better, but has a bit of an aged design now, and an insane 72 rounds. It doesn’t have as much love as BLAKE2 for instance, which makes it unlikely that people will build things competitive with BLAKE3 with it. SHA-3, BLAKE2b and BLAKE3 are the best. Like Skein, they are not vulnerable to length extension attacks, so they have a trivial keyed hash function construction. SHA-3 in particular has an elegant new design, the Sponge construction, which yields precise cryptographic protections in terms of the number of bits of security. It has displaced Merkle–Damgård as The Way We Do Things™ now; many modern hashes use it, eg Gimli relied on it to make comparisons. One of the great things about this form is that it makes it a XOF: you can make your hash as long as you desire. (BLAKE also shares this property, but with a different construction.) However, SHA-3 is slow, so if you want speed, use BLAKE2b (or Kangaroo12) over SHA-3, and BLAKE3 over them both. If you want to be conservative about security and don't care about speed, a safe bet is still SHA-512/256, which is safe against length extension attacks.