What is a UUID?

A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit label used to uniquely identify information in computer systems. The probability of generating duplicate UUIDs is so astronomically low that they can be assumed to be unique across all systems without requiring a central coordinator.

UUID Versions Explained

v4 — Random

Cryptographically random. Best for most use cases.

v1 — Time-based

Based on current time + MAC address (simulated).

v7 — Unix Time

Sortable by creation time. Ideal for database primary keys.

Common Use Cases

Database primary keys — especially UUID v7 for sortability
Session tokens and authentication
Idempotency keys in distributed systems
Tracking IDs for analytics events
File naming to avoid conflicts