UUID Generator

Universally Unique Identifier (UUID) is a standardized global unique identifier. Its main uses are as follows:

• Unique Identification: UUID is designed to provide unique identification in distributed systems. Each UUID is unique and will not conflict with other UUIDs.
• Decentralized Management: UUIDs do not require a central registry or coordination process to ensure their uniqueness. They can be generated independently by any person or organization.
• High Availability: UUIDs can be generated at any time, anywhere, without conflicting with UUIDs in other systems.
• Efficiency: UUIDs can be generated quickly, without needing to query a database or network service.
• Widespread Application: UUIDs are widely used in various fields, such as computer programs, databases, messaging systems, to uniquely identify different objects.

The specific format of a UUID is a 32-bit number, typically divided into 5 parts separated by hyphens, such as "550e8400-e29b-41d4-a716-446655440000".

UUID is a simple and effective identification solution that is widely used in software development and system design. It can ensure uniqueness while also having high generation speed and distributed characteristics.

There are several main versions of UUID:

• Version 1 (time-based): This is the earliest UUID version, using the current time and MAC address to generate the UUID. It can ensure that UUIDs are unique over time.
• Version 2 (DCE security): This version adds security mechanisms based on Version 1, suitable for the POSIX environment. It includes the UID or GID of the UUID owner.
• Version 3 (name-based, MD5): This version uses a namespace ID and a name as input, generating the UUID through the MD5 hashing algorithm. It is suitable for generating deterministic UUIDs based on names.
• Version 4 (random): This version generates UUIDs completely randomly, without relying on any input data. It is most suitable for scenarios requiring high randomness.
• Version 5 (name-based, SHA-1): This version is similar to Version 3, but uses the SHA-1 hashing algorithm instead of MD5. It is also suitable for generating deterministic UUIDs based on names.

Among these, Version 1 and Version 4 are the most commonly used UUID versions:

• Version 1 is suitable for application scenarios that require time-ordered UUIDs, such as database primary keys.
• Version 4 is suitable for application scenarios that require high randomness, such as temporary file names or session IDs.

The other versions also have their uses in specific scenarios, such as Version 2 for the POSIX environment, and Versions 3 and 5 for generating UUIDs based on names. Overall, the different UUID versions provide rich choices for developers.