UUID generator
Random UUID v4 identifiers, one or a batch.
Pure randomness, the usual choice.
Up to 500.
Check a UUID
The identifiers are created right in your browser by a cryptographically secure generator; they are never sent anywhere and never stored. Use version 7 where a UUID is a database key: it sorts by creation time, so the index does not fragment.
- Runs right in your browser
- Free, no sign-up
More about UUID generator
What a UUID is
A UUID is a 128-bit identifier written as 32 hexadecimal characters in five groups. The point of it is that anyone can generate one themselves and still not collide with someone else's: the chance of two random version 4 UUIDs meeting is so low that in practice nobody plans for it.
Version 4 or version 7?
Version 4 is purely random and the default choice. Version 7 carries the creation time in its first 48 bits, so the identifiers can be sorted by age. In a database that has a practical effect: the index fills up at the end instead of randomly across the whole structure, which saves both writes and space.
Frequently asked questions
Are the generated UUIDs secure?
They come from the browser's cryptographically secure generator, not from Math.random. They are never sent anywhere and never stored, so only your computer has seen them.
Can I use one as a secret token?
Version 4 has 122 random bits, which is enough for a one-off link. Be careful with version 7: the creation time in it is readable, so it makes a poor secret.
What does a UUID of all zeros mean?
That is the nil UUID, used as “no value” where a column cannot be empty. The checker therefore treats it as valid.