UUID Generator (v4)
Generate random RFC 4122 version-4 UUIDs — one or a whole batch. Choose case and hyphenation, then copy. Everything is produced locally in your browser and never transmitted.
About version-4 UUIDs
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier written as 32 hexadecimal digits grouped as 8-4-4-4-12, for example f47ac10b-58cc-4372-a567-0e02b2c3d479. They let independent systems mint identifiers that will not clash without any central coordinator — perfect for database keys, request IDs, file names and distributed systems.
Version 4 is the fully random flavour. Of the 128 bits, 6 are fixed to mark the version and variant, leaving 122 random bits. In the string you can spot this: the first digit of the third group is always 4 (the version) and the first digit of the fourth group is always 8, 9, a or b (the variant). This tool sets those bits correctly.
Where your browser supports it, we call crypto.randomUUID(); otherwise we build the UUID from crypto.getRandomValues() and set the version and variant bits by hand. Either way the random bytes come from your device's cryptographic RNG and never leave it. No server, no logging, no storage.
When to use v4 UUIDs
- Database primary keys that can be created offline or across many services without collisions.
- Correlation / request IDs for tracing a request through logs.
- Idempotency keys and unique file names.
Because v4 UUIDs are random rather than time-ordered, they are not ideal as clustered index keys in some databases — but for uniqueness they are excellent. To learn how identifiers and addresses underpin networking, see what an IP address is. Need a different kind of secret? Try the token generator or the password generator.
Frequently asked questions
What is a version-4 UUID?
A UUID (Universally Unique Identifier) is a 128-bit value written as 32 hexadecimal digits in the pattern 8-4-4-4-12. Version 4 means almost all of those bits are random. The 13th digit is always 4 (the version) and the 17th is one of 8, 9, a or b (the variant).
Are these UUIDs really unique?
A v4 UUID has 122 random bits, so the chance of two ever colliding is astronomically small — you would need to generate billions of UUIDs before a collision became even remotely likely. For practical purposes they are unique.
Is anything sent to a server?
No. UUIDs are generated locally with crypto.randomUUID or crypto.getRandomValues in your browser. Nothing is uploaded, logged, or stored. The tool works fully offline.
Can I generate many UUIDs at once?
Yes. Set the count and press generate to produce a batch, then use Copy all to grab the whole list. Each line is an independent random UUID.
Want the theory? Read the guides → · Visit the zoo →