How to Generate and Use UUID v4 in Web Applications

A Universally Unique Identifier (UUID) is a 128-bit label used for information in computer systems. Version 4 UUIDs are generated using random numbers.

Structure of a UUID v4

A standard UUID v4 contains 36 characters including 4 hyphens:

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx

• The 4 indicates version 4 (randomly generated).
• The y is always one of 8, 9, a, or b per RFC 4122.

Generating UUID v4 in the Browser

Modern JavaScript runtimes support generating UUIDs natively using the crypto global:

const uuid = crypto.randomUUID();
console.log(uuid); // -> "e8555e5c-74a4-47c3-bb0d-f0bb50d6063b"

This uses a cryptographically secure random number generator (CSPRNG), ensuring collision probability is virtually zero.