UUID generator

Generate UUIDs — random v4, time-ordered v7, legacy v1, or the all-zero nil. Make one or a whole batch, choose upper or lower case, and keep or drop the hyphens. Everything runs in your browser — the values are generated locally and nothing is uploaded.

What this does

A UUID (universally unique identifier, also called a GUID) is a 128-bit value written as 32 hexadecimal digits in five hyphen-separated groups, like f47ac10b-58cc-4372-a567-0e02b2c3d479. They let independent systems mint identifiers that won't collide without any central coordination.

v4 is almost entirely random and is the right default for most uses. v7 puts a millisecond timestamp in the high bits so the values sort by creation time — that locality makes them far kinder to database indexes than v4, which is why they're increasingly used as primary keys. v1 is the older time-based scheme (here the node is random, not a hardware address). The nil UUID is all zeros, useful as a placeholder or "no value" sentinel. v4 and v7 are generated from a cryptographically secure random source.