Question 1

What is a UUID?

Accepted Answer

UUID stands for Universally Unique Identifier. It is a 128-bit value used to uniquely identify information without coordination between systems. A version 4 UUID is generated using random numbers and looks like this: 550e8400-e29b-41d4-a716-446655440000.

Question 2

How unique is a UUID v4?

Accepted Answer

Version 4 UUIDs use 122 bits of randomness. The probability of generating two identical UUIDs is astronomically small — roughly 1 in 5.3 undecillion. In practice, collisions are so rare they can be treated as impossible for any application.

Question 3

What is the difference between UUID versions?

Accepted Answer

UUID v1 is based on the current timestamp and MAC address. UUID v3 and v5 are namespace-based hashes (MD5 and SHA-1 respectively). UUID v4 is randomly generated and is the most commonly used version. UUID v7 is a newer standard that combines timestamp and randomness for sortability.

Question 4

Is crypto.randomUUID() secure?

Accepted Answer

Yes. The browser's crypto.randomUUID() method uses a cryptographically secure random number generator (CSPRNG), the same source used by crypto.getRandomValues(). The generated UUIDs are suitable for security-sensitive uses such as session tokens or API keys.

Question 5

Are the UUIDs generated on a server?

Accepted Answer

No. UUIDs are generated entirely in your browser using the Web Crypto API. Nothing is sent to any server. The UUIDs are not logged, stored, or transmitted anywhere.

UUID Generator

When to use this

Database primary keys

API request IDs

Test data generation

Free UUID v4 generator — instant, private, no sign-up

Quick answers

Related tools