UUID Generator

A version-4 UUID is 122 bits of randomness plus 6 fixed bits:

1. 16 random bytes are drawn from crypto.getRandomValues() — the browser's cryptographically secure RNG.
2. Byte 6 is masked to 0100 in its high nibble (the version digit — always 4).
3. Byte 8 is masked to 10xx in its high bits (the RFC 4122 variant).
4. The bytes are rendered as 32 hex digits in the 8-4-4-4-12 pattern, e.g. xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where y is 8, 9, a or b.

With 122 random bits, the chance of two generated UUIDs colliding is negligible for any practical purpose.

Click Generate with the count set to 1 and you'll get something like 3f6a8b2c-9d4e-4f1a-8b7c-2e5d9a0f4c6b (your actual value will differ — that's the point). Note the 4 at the start of the third group (version) and the 8/9/a/b at the start of the fourth group (variant).

Each row is an independent random v4 UUID — use them as primary keys, idempotency keys, file names or test fixtures. Copy grabs one; Copy all grabs the batch as newline-separated text, ready to paste into a seed script or spreadsheet.

These are random, not sequential: don't use them where ordering matters, and don't use UUIDs as a substitute for real secrets — they're unique, not unguessable-by-design for security purposes (though 122 bits of entropy is plenty for nonces).