UUID generator

How to use it

1. Choose how many UUIDs you need, from one to a hundred.
2. Press New for a fresh set.
3. Press Copy (or Copy all) and paste them where you need them.

What a version 4 UUID is

A 128-bit identifier written as 32 hexadecimal digits in five groups, of which 122 bits are random. The third group always starts with 4 — that is the version — and the fourth with 8, 9, a or b, which is the variant. Both are fixed by the standard (RFC 9562, formerly 4122), and a UUID that gets either wrong will be rejected by a strict database column or parser even though it looks right.

These come from your browser’s own crypto.randomUUID(), with the same cryptographic source the password generator uses. The chance of any two of them colliding is one in 2¹²²; across a whole collection, you would need to generate a billion a second for about 86 years before the chance of a single repeat reached 50%.

When to use a different version

Version 4 is the right default for almost everything: API keys’ public halves, idempotency keys, correlation ids. The one place it costs you is as a database primary key at scale, where its randomness scatters inserts across the whole index. For that, version 7 puts a timestamp in the leading bits so ids are roughly time-ordered; most databases and libraries now generate it for you, and it is a change to make on the server rather than one this page needs to offer.