UUID v4 Generator

A version 4 UUID is 128 bits of which 122 are random - four bits are fixed to mark the version and two more to mark the variant. That is why every v4 UUID has a 4 at the start of the third group and one of 8, 9, a or b at the start of the fourth.

With 122 random bits, collisions are not a practical concern. You would need to generate billions per second for many years before the probability became worth thinking about, which is why v4 is the default choice for identifiers that need no ordering.

The security of that claim rests entirely on the random source. A UUID generated from Math.random is not 122 bits of entropy and should never be used as a token, a session ID or anything else where guessing it matters.

V4 UUIDs carry no timestamp and no ordering, so a table keyed by one has no natural sort and, in databases that cluster on the primary key, inserts land at random positions and fragment the index. Discord's snowflakes solve exactly this by encoding time in the high bits.

They are also long. 36 characters in the canonical hyphenated form is fine in a database column and awkward in a URL a human has to read or type. If the identifier is user-facing, a shorter scheme is usually kinder.

Discord bots use UUIDs in audit logs, webhook IDs and internal systems. Developers use them as primary keys in databases. Anywhere you need a globally unique identifier with practically no risk of collision, a UUID v4 is the right answer.

A version 4 UUID contains 122 random bits and 6 fixed bits. The version nibble is always 4 and the variant bits are always 10, which is why the third group always starts with a 4 and the fourth group always starts with 8, 9, a or b.