UUID v5 generator

The Randogram UUID generator produces a universally unique identifier of version 5.

Version 5 works like version 3 but uses SHA-1 instead of MD5 — this is the one the standard recommends for new work. The same name in the same namespace always yields the same identifier. Here the name is random, so the result differs every time.

You can also use the public UUID generator API

Questions and answers

How is version 5 better than version 3?

It computes the hash with SHA-1 instead of MD5, and this is the one the standard recommends for new work. The behaviour is the same: the same name in the same namespace always gives the same identifier.

Why does the result change on every run?

The name the hash is taken from is random here — the form asks for neither a namespace nor a name. If you need a reproducible identifier, compute it yourself from your own values: the same input will then always give the same result.

Is SHA-1 secure enough for identifiers?

Yes. The known attacks on SHA-1 make it possible to find two different messages with the same hash, which matters for signatures rather than for spreading names across a value space. If the identifier has to be unpredictable, take version 4 — it is built on randomness alone.