What is a UUID?
A UUID (universally unique identifier) is a 128-bit label written as 32 hex digits in five groups, such as 3f2b8c1e-9d4a-4e7b-a1c5-2d8f6b0e7a34. Developers use them as database keys, file names and request IDs because two systems can create them without talking to each other and still avoid clashes.
Version 4 explained
This tool makes version 4 UUIDs. 122 of the 128 bits are random, and the rest mark the version and variant. The chance of two random UUIDs matching is so small that you could generate billions a second for decades and still expect no duplicate.
Tips
- A UUID is an identifier, not a secret. Do not use it as a password. For that, use the password generator.
- Need a fingerprint of some text? The hash generator creates SHA hashes.
Frequently asked questions
Is a UUID the same as a GUID?
Yes. GUID is the name Microsoft uses. The format and the way they are made are the same.
Can two UUIDs ever be the same?
In theory yes, in practice no. With 122 random bits, the odds of a clash are far smaller than the odds of a hardware fault.
Are these UUIDs safe to use as database keys?
Yes, as unique identifiers. Random UUIDs are not sorted by time, which can slow some large indexes. Time-ordered versions exist for that case.
How random are they?
They come from your browser's cryptographically secure random generator (crypto.randomUUID or crypto.getRandomValues), not from Math.random.
What does version 4 mean?
The 13th hex digit is always 4 and the 17th is 8, 9, a or b. Those digits tell programs which UUID version and variant this is.