UUID Generator

What is a UUID?

A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify information in computer systems. The standard format is a string of 32 hexadecimal digits displayed in five groups separated by hyphens, for example: 550e8400-e29b-41d4-a716-446655440000. UUIDs are defined by RFC 4122 and are widely used in distributed systems, databases, and software development.

UUID Versions Explained

UUID v1 is generated using the host computer's MAC address and the current timestamp (in 100-nanosecond intervals since the UUID epoch). It provides temporal ordering but may expose the machine's identity.

UUID v4 is the most commonly used version. It generates a random UUID using a cryptographically secure pseudo-random number generator. The chance of a collision is astronomically low — approximately 1 in 2¹²², making it safe for virtually any use case.

UUID v7 is a newer standard that combines a Unix timestamp (in milliseconds) with random bits. This creates identifiers that are both unique and time-sortable, which improves database index performance compared to v4.

NIL UUID (00000000-0000-0000-0000-000000000000) is a special case used as a sentinel value representing "no UUID" or an uninitialized state.

Common Use Cases

UUIDs are used as primary keys in databases, session identifiers in web applications, transaction IDs in financial systems, and resource identifiers in REST APIs. They eliminate the need for a central coordinating authority to guarantee uniqueness.