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Definition

What is UUID (Universally Unique Identifier)?

A UUID is a 128-bit random identifier — written as 32 hex digits with dashes — that's unique enough to generate on any machine without coordination.

Also called: GUID · universally unique identifier

The most common form is version 4, which is essentially a big random number. Version 7, standardised in 2024, prepends a timestamp so IDs sort in creation order — much friendlier for database indexes.

UUIDs are used as primary keys, request IDs, session tokens, and anywhere two systems need to agree on an ID without a central issuer. Collisions are theoretically possible but astronomically unlikely.

They're 36 characters, so they take more space than an integer key. In hot paths, UUID v7 or a compact encoding (Base32, Base58) recovers most of the performance.

Try a tool that uses UUID (Universally Unique Identifier)

UUID Generator

Generate cryptographically random UUID v4 identifiers.

Hash Generator

Compute SHA-1, SHA-256, SHA-384, and SHA-512 hashes.

Password Generator

Create strong random passwords with custom rules.

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