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Uses crypto.randomUUID() — RFC 4122 version 4.
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value used to identify information without relying on a central authority to avoid duplicates. A version 4 UUID — the type this tool generates — is built almost entirely from random bits, which makes the chance of two ever colliding astronomically small (you'd need to generate billions of UUIDs per second for centuries before a collision became likely).
Every UUID follows the same 8-4-4-4-12 hexadecimal pattern, e.g. 3fa85f64-5717-4562-b3fc-2c963f66afa6. The 4 in the third group marks it as version 4, and the leading digit of the fourth group (8, 9, a, or b) marks the RFC 4122 variant.
Common uses for UUIDs
- Primary keys in databases, so records can merge from multiple sources without ID collisions
- Unique identifiers for API requests, sessions, or tracing IDs in distributed systems
- File names or object keys in storage systems (S3 buckets, CDNs) that need to be unguessable
- Test fixtures and mock data where you need unique but disposable IDs
Frequently asked questions
How random are these UUIDs?
This tool uses crypto.randomUUID(), a browser API backed by a cryptographically secure random number generator — the same class of randomness used for encryption keys, not a simple Math.random() fallback.
Can two UUIDs ever collide?
In theory yes, in practice no. With 122 random bits, you'd need to generate around 1 billion UUIDs per second for about 85 years before the probability of a single collision reached 50%.
What's the difference between UUID v1 and v4?
UUID v1 is derived from the current timestamp and the generating device's MAC address, which can leak information about when and where it was created. UUID v4, generated here, is purely random and reveals nothing about its origin.
Is my data sent to a server?
No. UUIDs are generated entirely in your browser using the Web Crypto API — nothing is transmitted anywhere.