A UUID (Universally Unique Identifier) is a 128-bit identifier that is guaranteed to be unique across both space and time, making it ideal for distributed systems and databases.

What's the difference between UUID versions?

UUID v1 uses timestamp and MAC address, UUID v4 uses random numbers, and NIL UUID is all zeros. Version 4 is most commonly used for its simplicity and randomness.

UUID Generator

Generate universally unique identifiers (UUIDs) or GUIDs for databases, software, and more.

UUID Version

Number of UUIDs to Generate

Generated UUID(s)

About UUIDs

A Universally Unique Identifier (UUID) is a 128-bit number used to uniquely identify information in computer systems. The term GUID (Globally Unique Identifier) is also commonly used, particularly in Microsoft implementations. The primary purpose of UUIDs is to enable distributed systems to uniquely identify information without significant coordination between them.

Technical Details of UUID Generation (Version 4)

Version 4 UUIDs are generated using a pseudo-random number generator. The algorithm replaces certain bits of the randomly generated number with fixed values to indicate the UUID version and variant. While the probability of two randomly generated UUIDs being the same is extremely low, it is not zero. However, for practical purposes, they are considered unique.

Applications of UUIDs

Database Primary Keys: Used as unique identifiers for records in distributed databases.
Distributed Systems: Identifying objects or transactions across multiple systems without central coordination.
File Naming: Generating unique filenames to prevent collisions.
Session IDs: Creating unique session identifiers for web applications.

Common Questions

Are UUIDs truly unique?

While not mathematically guaranteed to be unique (due to being pseudo-random), the probability of a collision (two identical UUIDs being generated) is so astronomically low that it's considered negligible for practical applications. You would need to generate trillions upon trillions of UUIDs for a reasonable chance of collision.

Can UUIDs be used for security purposes?

UUIDs are excellent for uniqueness but should not be relied upon for security purposes like encryption keys or authentication tokens. Their predictability (especially for versions other than v4) and lack of inherent cryptographic strength make them unsuitable for such uses. For security, use cryptographically secure random numbers.

What is the difference between UUID and GUID?

UUID and GUID are essentially the same thing. UUID is the standard term, while GUID is Microsoft's implementation and term for the same concept. They both refer to a 128-bit identifier designed for uniqueness.