Universally unique identifiers look simple: a 36-character string with four hyphens. Behind that string sits a careful design decision. Which version should your database use? Does your API need sortable keys? Should identifiers be guessable, or deterministic, or completely random? This blog exists to answer those questions with practical, code-first guidance rather than theory alone.
Every guide here pairs a plain-English explanation with the trade-offs that matter in production: index performance, collision probability, privacy implications of embedded timestamps, and what happens when two systems disagree on formatting. If you are building with PostgreSQL, MongoDB, REST APIs, message queues, or event-driven services, these articles will help you choose the right identifier strategy the first time.
A quick preview of what matters most: v4 UUIDs are random and reveal nothing about their origin, which makes them the safe default for most records. v7 UUIDs embed a timestamp, so they sort in insertion order and keep database indexes happy under heavy write load. v5 UUIDs are deterministic, meaning the same namespace and name always produce the same identifier, which is invaluable for stable references across systems. The guides below go into the detail behind each choice, including the edge cases where the standard leaves room for interpretation.
A full breakdown of the four versions developers actually use. How each one is constructed, when its characteristics help you, and where they create hidden risks like timestamp leakage or predictability.
July 13, 2026 • 8 min read
Read Article →Why globally unique keys matter when services generate identifiers independently. Database index behaviour, UUID v7 adoption, sharding considerations, and the coordination costs you avoid.
July 13, 2026 • 8 min read
Read Article →The difference between Microsoft's GUID and RFC 4122 UUIDs, byte-order quirks that break cross-platform systems, and how to keep identifiers interchangeable across .NET, Java, and web stacks.
July 13, 2026 • 8 min read
Read Article →These guides are written for working developers and data engineers who need a defensible answer to "which UUID should we use?" Each article is grounded in the RFC 4122 specification and real database behaviour, and every example can be reproduced with the free browser-based tool on this site.
Use the UUID Generator to generate and validate v1, v4, v5 and v7 identifiers while you read. The tool runs entirely in your browser, so nothing you generate ever leaves your machine.