Free UUID v4 vs v5 Differences

What is a UUID?

A Universally Unique Identifier (UUID) is a 128-bit label used for information in computer systems. They are designed to be globally unique without requiring a central registration authority, making them perfect for primary keys in distributed databases.

UUID Version 4: Randomness

Version 4 UUIDs are generated using completely random or pseudo-random numbers. Their generation requires no inputs, and the sheer volume of possiblities (2^122) means the chance of collision is almost mathematically zero. They are the standard for generating new session IDs or user records.

UUID Version 5: Name-Based

Version 5 UUIDs are generated deterministically by hashing a "namespace" identifier and a "name" via SHA-1. If you input the exact same namespace and name, you will always get the exact same UUID v5. This is highly useful for mapping known external data into a consistent UUID format without needing a lookup table.