UUID (Universally Unique Identifier) is a 128-bit number used to identify information in computer systems. The format is xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx with hexadecimal characters.

UUIDs are widely used for database record identification, session IDs, distributed systems, API keys, and transaction IDs. They are designed to be unique across systems without central coordination.

No, UUIDs should not be used as passwords or security tokens. They are predictable based on structure and timestamp. For secure random values, use a cryptographically secure random generator instead.

UUID v4 is a random UUID generated using cryptographically secure random numbers. It provides 122 bits of randomness, making collision extremely unlikely.

Most languages support UUID generation: JavaScript uses crypto.randomUUID(), Python uses uuid.uuid4(), Java uses UUID.randomUUID(), and C# uses Guid.NewGuid().