UUID Generator

What is a UUID?

A UUID (Universally Unique Identifier, sometimes called GUID) is a 128-bit number written as 32 hex digits in the canonical 8-4-4-4-12 shape — for example a1b2c3d4-e5f6-4a7b-9c0d-1e2f3a4b5c6d. The point is that any system can mint one with no coordination and the chance of collision is negligible. v4 is fully random; v7 embeds a millisecond timestamp at the start, so v7s sort chronologically and play much nicer with database B-tree indexes than v4s.

How to use this tool

Pick a version (v4 for opaque random IDs, v7 when you want time-ordering for primary keys), choose how many you need (1-100), pick lower or UPPERCASE, and hit Regenerate. Use Copy next to a row to grab one, or Copy all to dump them all to the clipboard, one per line. v4 uses the browser's crypto.randomUUID(); v7 is built locally from a 48-bit timestamp plus 74 random bits.

v4 vs v7 — which should I use?

Use v4 for tokens, request IDs, opaque public-facing identifiers, anywhere you don't want order or timing leaked. Use v7 for primary keys in modern databases — it gives you globally-unique IDs without random-insert index thrash, and rows naturally sort by creation time. Avoid v1 (leaks MAC address) and v3/v5 (name-based, niche use). Don't truncate UUIDs to "save space" — collisions ramp up fast.

UUID versions at a glance

All UUIDs are 128 bits and look the same on the wire; the version number (the first hex digit of the third group) tells you how they were minted.

Frequently asked questions