How to use it
Pick type and count
Version 4 is fully random; version 7 starts with the time, so it sorts by creation.
Pick the format
With or without hyphens, uppercase, or quoted with commas to paste into code or SQL.
Copy or download
Copy the list or download it as a text file.
v4 or v7?
| Version 4 | Version 7 | |
|---|---|---|
| Content | 122 random bits | Millisecond time + 74 random bits |
| Order | Random | By creation time |
| As a database primary key | Scatters the index, slower inserts | Faster inserts and indexing |
| Reveals creation time? | No | Yes |
Good to know
Odds of a duplicate. With v4 you would need about 2.7 quintillion IDs for a 50% chance of a single repeat, so it is unique in practice.
v7 reveals the time. The first 12 hex digits are the creation time. If that matters, use v4.
UUID vs GUID. Same thing: GUID is Microsoft’s name, often written in uppercase inside { }.
FAQ
What is a UUID?
A 128-bit identifier written as 32 hex digits in five groups, like 550e8400-e29b-41d4-a716-446655440000, that systems create without coordinating, yet practically never repeat.
Are these really random?
Yes. We use crypto.getRandomValues, your browser’s cryptographically secure random generator.
How do I tell a UUID’s version?
The first digit of the third group is the version: xxxxxxxx-xxxx-7xxx-... is version 7. Paste it into the checker to see its version and creation time where it has one.
Are the UUIDs I create stored?
No. They are made in your browser and never sent anywhere.