What is a UUID? Complete Guide to Universally Unique Identifiers

A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. Also known as GUID (Globally Unique Identifier), UUIDs are designed to be unique across all devices and time without requiring a central registration authority.

What Does a UUID Look Like?

UUIDs are typically displayed as 32 hexadecimal characters separated by hyphens into five groups:

550e8400-e29b-41d4-a716-446655440000

This format follows the pattern: 8-4-4-4-12, representing 36 characters total (32 hex digits + 4 hyphens).

Why Use UUIDs?

• Global uniqueness: Generate IDs without coordinating with a central server
• Distributed systems: Perfect for microservices and distributed databases
• Security: Harder to guess than sequential IDs
• Merge-friendly: No conflicts when combining data from different sources
• Offline generation: Create IDs without network connectivity

UUID Versions

There are several UUID versions, each with different generation methods:

• Version 1: Based on timestamp and MAC address
• Version 3: Name-based using MD5 hashing
• Version 4: Randomly generated (most common)
• Version 5: Name-based using SHA-1 hashing

Common Use Cases

UUIDs are used extensively in software development for database primary keys, API request tracking, session identifiers, file naming, message queue identifiers, and distributed transaction IDs.