UUID Generator
Generate RFC 9562 UUIDv4 identifiers from cryptographically secure browser randomness, one value at a time.
Generated UUIDv4
Generate a UUIDv4 to see the canonical 8-4-4-4-12 hexadecimal form.
Generated locally
The identifier is created in your browser. No UUID value is sent to Yoryantra for generation or storage.
Identifier, not authentication secret
UUIDv4 is designed for identifiers. Do not treat a UUID alone as proof of identity, authorization, ownership, or access permission.
What the browser actually generates
RFC 9562 defines UUIDv4 as a 128-bit UUID whose version field is set to 4 and whose RFC variant bits are set to 10. The remaining 122 bits come from random or pseudorandom data. That fixed bit layout is why a version 4 UUID has 4 in the version position and one of 8, 9, a, or b in the variant position.
Modern browsers expose crypto.randomUUID(), which returns a cryptographically secure UUIDv4. The fallback path here uses crypto.getRandomValues() and sets the same version and variant bits explicitly when randomUUID() is unavailable.
Uniqueness is probabilistic, not a database guarantee
UUIDv4 leaves an enormous random space, so accidental collisions are extraordinarily unlikely when a sound random source is used. Still, the standard does not turn probability into an absolute guarantee. Applications that require hard uniqueness should keep the database constraint or duplicate check that the data model already needs.
Where UUIDv4 fits well
- Database primary or public identifiers when random ordering is acceptable.
- Correlation IDs for tracing requests across logs and services.
- Client-created object IDs when separate systems must create identifiers independently.
- Test fixtures where a standards-shaped random identifier is preferable to a sequential number.
For write-heavy databases where insertion order matters, UUIDv7 may be a better design choice because RFC 9562 places a Unix-epoch timestamp in the most significant bits. This page intentionally generates UUIDv4 only; it does not disguise a different scheme as version 4.
What a UUID does not tell you
A UUID string does not prove who created it, whether a referenced record exists, whether the holder may access that record, or whether an identifier was generated by a trusted source. UUIDv4 also carries no timestamp or application metadata that can be recovered from the value.
References for the exact format
RFC 9562 is the current UUID specification and replaces RFC 4122. MDN documents the browser Crypto.randomUUID() method and its secure-random UUIDv4 behavior.