UUID Generator

A UUID (Universally Unique Identifier) is a 128-bit value, usually written as 32 hex digits split into five groups like `xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx`. This generator produces version 4 UUIDs, the random variant, using the browser's crypto.randomUUID() — a cryptographically secure random number generator built into the Web Crypto API, rather than a weaker Math.random()-based approach some libraries fall back on.

Version 4 encodes almost no information beyond randomness: 122 of its 128 bits are random, with the remaining 6 bits fixed to mark the UUID version and variant per the RFC 4122 spec (that's why every v4 UUID has a '4' in the same position and a restricted set of characters right after it). With 122 random bits, the odds of two independently generated v4 UUIDs colliding are astronomically small — small enough that collision risk is not a practical concern even at enormous scale, which is why UUIDs are trusted as unique identifiers without a central coordinating authority.

They're commonly used as database primary keys, request or trace IDs for debugging distributed systems, filenames that need to avoid collisions, or any identifier that multiple independent systems need to generate without checking in with each other first.

A UUID is 128 bits shown as 32 hex digits in the pattern 8-4-4-4-12. Version 4 uses 122 random bits, and 6 bits are fixed to mark the version and variant.

Collisions are possible in theory but astronomically unlikely: you would need to generate about 2.7 billion billion UUIDs for a 50% chance of one duplicate. Random UUIDs are poor database primary keys on some engines because they scatter inserts, where time-ordered variants such as UUIDv7 index better.