UUID Guide: Versions, Formats, and Best Practices

UUIDs (Universally Unique Identifiers) are 128-bit identifiers that are unique across space and time. They are essential for distributed systems where centralized ID generation is impractical.

UUID Versions

Version 1 uses the current timestamp and MAC address. Version 4 is completely random and most commonly used. Version 5 generates deterministic IDs from a namespace and name using SHA-1. Version 7 is time-ordered and gaining popularity for database use.

UUID Format

A standard UUID looks like: 550e8400-e29b-41d4-a716-446655440000. It consists of 32 hexadecimal digits in five groups separated by hyphens (8-4-4-4-12). The version number is encoded in the third group.

When to Use UUIDs

Use UUIDs when you need IDs generated without a central authority, when merging data from multiple sources, for distributed databases and microservices, and when sequential IDs would leak information about your system.

Performance Considerations

UUIDs are larger than auto-incrementing integers (16 bytes vs 4-8 bytes). Random UUIDs (v4) can cause index fragmentation in B-tree databases. Consider UUID v7 for better index performance due to time-ordering.

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