Generate random version 4 UUIDs (also called GUIDs), one at a time or in bulk.
A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier) on Windows/.NET, is a 128-bit identifier standardized in RFC 4122. A version 4 UUID (the most common variant, generated here) is built from random bits, formatted as 32 hexadecimal digits in five groups separated by hyphens (8-4-4-4-12), e.g. f47ac10b-58cc-4372-a567-0e02b2c3d479. The odds of two random v4 UUIDs colliding are astronomically small — about 1 in 2.71 × 10¹⁸ for any given pair — which is why they're used as database primary keys, request/trace IDs, and session tokens without a central coordinator handing out sequential numbers.