UUID Versions
- v1 ??time + MAC address. Sortable by creation time but reveals the host's MAC.
- v3 ??MD5 hash of a namespace + name. Deterministic.
- v4 ??pure random. The most common variant. ~5횞10쨀??unique values.
- v5 ??SHA-1 hash of namespace + name. Deterministic, preferred over v3.
- v6/v7/v8 ??newer (RFC 9562, 2024). v7 embeds Unix time, giving sortable yet random UUIDs.
Format
Standard text representation is 36 characters: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. The M nibble (position 14) is the version. The two highest bits of N (position 19) are the variant ??for RFC-compliant UUIDs they are 10, meaning the first hex digit of group 4 is 8, 9, a, or b.
Randomness
This tool uses the browser's crypto.randomUUID() when available (Chrome 92+, Firefox 95+, Safari 15.4+), with a crypto.getRandomValues fallback for older browsers. Both rely on the operating system's cryptographic random number generator, suitable for security-sensitive use.