UUID Generator
A UUID (Universally Unique Identifier, RFC 9562) is a 128-bit identifier with negligible collision probability. This tool generates v4 (random — the default), v7 (unix-ms timestamp + random, sortable by creation time), v1 (time + random node), and v5 (SHA-1 hash of namespace + name, deterministic). Up to 100 at a time, all generated locally via crypto.getRandomValues and the Web Crypto API.
Switch to the Inspect tab to paste an existing UUID and read its version, variant, and any embedded timestamp — useful for debugging cases where the wrong UUID flavour is being passed across services.
Which version should I use?
v4 — the default
Pure random, 122 bits of entropy. Good when you don't need ordering and just want a unique key. Practically zero collision risk for any realistic load.
v7 — sortable
Embeds a 48-bit unix-ms timestamp at the start, so v7s sort lexicographically by creation time. Better than v4 as a database primary key — keeps B-tree inserts cheap and gives you a free creation timestamp. Use for new schemas.
v5 — deterministic
SHA-1 hash of a namespace UUID + a name string. The same input always produces the same UUID — useful for content-addressable IDs (e.g. derive a UUID from a URL or a hostname).