UUID

UUID (Universally Unique Identifier) is a 128-bit identifier that is unique across space and time. It is commonly used for database primary keys and distributed systems.

UUID v1 uses timestamp and MAC address, v4 is random, v5 uses namespace and name hashing. V4 is most common for general use due to its simplicity and randomness.

Theoretically yes, but practically no. The probability of UUID v4 collision is astronomically low (about 1 in 2^122), making it safe for most applications.