UUID Generator
Generate version 4 UUIDs from the browser cryptographic source, in bulk, with nothing sent anywhere.
Runs entirely in your browser — nothing is uploaded
Up to 500 at a time.
Version 4, from the right source
A version 4 UUID is 122 random bits with six fixed. Its whole value rests on those bits actually being random, which is why this uses the browser’s cryptographic generator rather than assembling one from Math.random.
Math.random is specified only as implementation-dependent, and identifiers built from it have collided in production more than once. It is the shortcut worth not taking.
How unique is unique
Enough that collisions are not a practical concern. You would need to generate roughly a billion UUIDs a second for about 85 years to have a 50 per cent chance of one collision.
That is a statement about version 4 specifically, and it depends entirely on the randomness being real — which brings it back to the point above.
Version 4 is not always the right one
A v4 UUID is random, so a table indexed on it gets no locality — consecutive inserts land in unrelated places and large indexes fragment.
For database keys at scale, a time-ordered identifier such as UUID v7 or ULID is usually the better choice. Version 4 is right for everything else: request identifiers, file names, anything that just has to be distinct.
Nothing is sent anywhere
Everything on this page happens in your own browser. No request is made, nothing is stored between visits, and the page keeps working with the connection switched off.
Frequently asked questions
What is the difference between a UUID and a GUID?
None that matters. GUID is Microsoft's name for the same 128-bit identifier. The formats are identical and the terms are used interchangeably.
Are these safe to use as secrets?
No. A UUID is unique, not unpredictable in the way a secret needs to be, and it is usually visible in URLs and logs. Use a password or token generator for anything that has to be secret.
Why is there a 4 in the third group?
That digit identifies the version. Every version 4 UUID has it, and the first character of the fourth group is always 8, 9, a or b — those are the six fixed bits.
Are the UUIDs sent anywhere?
No. They are generated in this tab and never leave it.