UUID 產生器

A UUID (universally unique identifier) is a 128-bit value used to label things, database rows, files, events, messages, API resources, without a central authority handing out IDs. Any machine can mint one independently and trust it will not clash with anyone else's.

This generator produces version 4 UUIDs, the most common kind. A v4 UUID is almost entirely random: 122 of its 128 bits come from a random source, with the remaining 6 bits fixed to mark the version and variant. It is written as 32 hexadecimal digits in the familiar 8-4-4-4-12 grouping.

Each batch of five is generated with your platform's cryptographically secure random source, the same one used for security-sensitive randomness, not a predictable pseudo-random function. Press Run again any time for a fresh batch.

Uniqueness is a matter of probability rather than a hard guarantee, but the numbers are reassuring: with 122 random bits you would need to generate billions of UUIDs before the chance of a single collision became meaningful. For practically every application this is effectively unique.

Version 4 is the right default when you just need a unique ID. If ordering matters, version 7 encodes a timestamp in its leading bits so IDs sort by creation time, which keeps database indexes tidier than fully random v4 keys. The Learn article on v4 vs v7 covers the trade-off in depth.

Common uses include primary keys, idempotency keys that make a request safe to retry, correlation IDs for tracing a request across services, and unique file names. Keep in mind that a v4 UUID is random but not secret, so it should not be used on its own as a security token or password.