When discussing ID generation in software, you may have heard of a UUID. What are they? Are they useful? What are the different versions? Let's explore that.

Playful Programming

UUIDs (Universally Unique Identifiers) are 128-bit numerical values used to uniquely identify digital resources without requiring knowledge of previously generated IDs. All UUIDs share a common hexadecimal string format with embedded version and variant metadata. The five official UUID versions each serve different purposes: UUIDv1 combines a MAC address and timestamp (useful for network tracking but exposes system identity); UUIDv2 is rarely used due to collision issues and poor documentation; UUIDv3 and UUIDv5 generate deterministic IDs by hashing a namespace and name (MD5 vs SHA-1 respectively), ideal for stable reproducible IDs; and UUIDv4 uses random data, making collisions practically impossible and requiring no input metadata. Guidance is provided on when to choose each version based on security, performance, and use case requirements.

What are UUIDs?