UUID Version 4

A UUID (Universally Unique Identifier) is a 128-bit number that identifies information in computer systems. Version 4 UUIDs are the most common type of UUID. They use random numbers that have an extremely low chance of collision, making them perfect for creating unique identifiers without coordination between systems.

Format

A version 4 UUID consists of 32 hexadecimal digits displayed in five groups separated by hyphens (8-4-4-4-12 format). The first three groups contain random data, while the fourth group starts with a '4' to indicate the UUID version. The fifth group begins with one of eight specific characters (8, 9, A, or B) to show it's a variant 1 UUID. This structure ensures each UUID is unique while maintaining a consistent format.

Applications

Version 4 UUIDs work well for distributed systems that need to generate IDs without coordination. They're ideal for session IDs, database keys, and file names. While UUID v7 (which includes a timestamp) offers better sorting and database performance, v4 remains popular for its simplicity and collision resistance. Choose v4 when you need unpredictable identifiers and don't require time-based ordering.

Learn more about how UUID v4 compares to other versions in our comprehensive UUID comparison.