What is a UUID
A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier used to name records in a way that is practically unique, without relying on a central database to avoid collisions. It's widely used as a primary key in distributed databases, session identifiers and API keys.
How it's generated (version 4)
UUID version 4 is generated from random numbers (using the browser's cryptographically secure crypto.getRandomValues API), with only a few fixed bits to identify the version and variant — the probability of collision between two v4 UUIDs is negligible in practice.
Format
A standard UUID has 36 characters, in the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where x is a random hexadecimal digit, the "4" indicates the version, and y is one of 8, 9, a or b (indicating the variant).
Frequently asked questions
Can the generated UUIDs repeat?
The probability is astronomically low — a v4 UUID has 122 bits of randomness, so collisions are practically impossible in practice.
Does this generator work offline / without sending data to a server?
Yes — the UUIDs are generated entirely in your browser, using the native cryptographic API, with no communication with the server.