Learn about UUIDs & GUIDs

Plain-English guides to how unique identifiers work, the standards behind them, and how to pick the right version for your project.

Basics

An introduction to UUIDs: what they are, why they exist, and where you'll encounter them in everyday software.

Basics

UUID and GUID describe the same 128-bit identifier - here's where the naming difference comes from and whether it matters.

Standard

A breakdown of the IETF standard that defines UUID structure, versions, and variants - and how RFC 9562 supersedes it.

Comparison

Random vs sortable identifiers - how each version is built, and which one fits your database schema.

Reference

The anatomy of a UUID string, its 128-bit storage size, and the real-world odds of a collision.