UUID

Where it came from

UUIDs trace to the Apollo Network Computing System (1980s) and were standardized for DCE/RPC in the 90s; Microsoft popularized them as GUIDs in COM. After 30 years of ad-hoc versions, RFC 9562 (2024) finally documented the whole family — including the modern time-ordered v6/v7/v8.

How it works

A UUID is 128 bits with version semantics:

v1/v6 — timestamp + MAC address (privacy concern: leaks the MAC);

v3/v5 — hash of a name in a namespace (MD5/SHA-1), deterministic;

v4 — 122 random bits, the default everywhere;

v7 — millisecond timestamp + randomness, sortable and database-friendly;

v8 — vendor-custom.

Collision odds for v4 are famously negligible: you'd need to generate a billion UUIDs per second for a century to reach ~50% probability.

UWC generates every version with CSPRNG and verified RFC test vectors — offline, in your browser.