UUID

It is a 128-bit identifier standardized by the Open Software Foundation (OSF) to create unique identifiers for digital objects. UUIDs are commonly used in various information systems and are particularly useful in distributed systems where unique identifiers are needed without central coordination.

UUIDs are generated using algorithms designed to ensure uniqueness across space and time, even in distributed systems where multiple UUIDs might be generated concurrently. The structure of a UUID is standardized, consisting of 32 hexadecimal digits displayed in five groups separated by hyphens, like this: 8-4-4-4-12, where each digit represents four bits.

There are several versions of UUIDs, each generated using different algorithms, and they have different properties and intended uses:

Version 1 (UUID based on timestamp and MAC address): This version uses the current timestamp and the MAC address of the computer generating the UUID to create a unique identifier. It is primarily used in scenarios where uniqueness and time-based sorting are essential.
Version 2 (DCE security version): Similar to version 1 but with modifications to include POSIX UID/GID.
Version 3 (MD5 hash of a namespace and name): This version generates UUIDs based on a namespace identifier and a name. It uses the MD5 hashing algorithm to produce the UUID. This version is deterministic; given the same namespace and name, it will always produce the same UUID.
Version 5 (SHA-1 hash of a namespace and name): Similar to version 3 but uses the SHA-1 hashing algorithm instead of MD5. Like version 3, it is deterministic.
Version 4 (Randomly generated UUID): This version generates UUIDs using random or pseudo-random numbers. It provides a high probability of uniqueness. It is widely used in various applications where uniqueness is the primary concern.

The differences between these versions primarily lie in the algorithms used for generation, the sources of randomness, and the properties of the resulting UUIDs, such as determinism and uniqueness guarantees. Each version is suitable for different use cases depending on the requirements for uniqueness, determinism, and collision resistance.