UUID v4
crypto.getRandomValues in your browser.About UUID version 4
Generate random version-4 UUIDs in your browser. UUID v4 reserves version and variant bits and fills the remaining 122 bits from a cryptographically secure random source when the browser supports crypto.randomUUID.
Formula and method
The standard text form contains 32 hexadecimal digits in an 8-4-4-4-12 grouping.
Worked example
A UUID looks like 9f4c0f28-8c16-4f38-a772-6d68e3869f16; each generated value should be treated as opaque.
How to interpret the result
A version-4 UUID is designed to be generated independently with an extremely low collision probability. Its format carries version and variant information but no creation time or business meaning. Store it as an opaque identifier and compare the complete value rather than extracting meaning from individual characters.
Important limitations
- UUIDs are excellent identifiers but are not authentication secrets.
- Collision probability is extremely low, not mathematically zero.
Common questions
Can a UUID be used as a password or access token?
No. Uniqueness is not the same as secrecy. UUIDs can appear in logs and URLs, and an identifier should not be the only control protecting sensitive data.
Are generated UUIDs guaranteed unique?
No random identifier has a mathematical guarantee without coordination. With a secure random generator the collision probability is extremely small, which is sufficient for typical identification uses.
Related tools
Method and examples reviewed September 8, 2026.