Formula
v4: 122 random bits + version and variant bitsv7: 48-bit Unix millisecond timestamp + random bits + version and variant bits
- Format: 8-4-4-4-12 hexadecimal digits.
A UUID is a 128-bit number written as 32 hex digits.
Worked example
One v4 UUID
- How many
- 1
- Version
- Version 4 — random
- Letters
- lowercase
- Hyphens
- Include hyphens
UUID
e75cca50-e322-486a-a6cd-629160123b64
Version: 4 (random)
Count: 1
e75cca50-e322-486a-a6cd-629160123b64
UUIDs are random, so a new value is created every time — the example above is only a sample.
How it works
Version 4 UUIDs are random: 122 of the 128 bits come from the secure random generator (crypto.getRandomValues), so collisions are astronomically unlikely. Version 7 puts the current time in the first 48 bits so values sort in creation order, which keeps database indexes tidy; the rest is random.
Generation happens in your browser and nothing is sent anywhere or stored — but a UUID is an identifier, not a secret, so don't use one as a password or token. Press Generate again for a new batch. To decode or inspect tokens see the JWT Decoder; for timestamps see the Unix Timestamp Converter.
Assumptions and limits
- Up to 100 per click.
- UUIDs aren't secrets; don't use them as access tokens.