UUID generator
Generate random v4 or time-ordered v7 UUIDs, one or up to a thousand at once.
How it works
A UUID is 128 bits written as 32 hex digits in groups of 8-4-4-4-12. In v4 122 bits are random; in v7 the first 48 bits are the Unix time in milliseconds and the rest is random. Both set the version digit (the 13th) and the variant bits.
Worked example
- v4: 3f1c9b7a-2d4e-4c1b-9a6f-8e2d5c7b1a03
- the “4” after the second dash is the version
- the 8, 9, a or b after the third dash is the variant
Frequently asked questions
Which version should I use, v4 or v7?
v4 is fully random and the usual choice. v7 starts with the current time in milliseconds, so new IDs sort after older ones; database indexes like that better.
Can two UUIDs ever be the same?
In practice no. A v4 UUID has 122 random bits; you would need to create about a billion per second for 85 years to reach a 50% chance of one duplicate.
Are these UUIDs safe to use?
They are created in your browser with crypto.getRandomValues, a cryptographically secure generator, and never leave your device.