A Version 4 UUID is a universally unique identifier that is generated using random numbers. The Version 4 UUIDs produced by this site were generated using a secure random number generator.
A Version 1 UUID is a universally unique identifier that is generated using a timestamp and the MAC address of the computer on which it was generated.
A Version 5 UUID is a name-based universally unique identifier generated using a SHA-1 hash of a namespace identifier and a name. The same namespace and name will always produce the same Version 5 UUID.
A Version 7 UUID is a time-ordered universally unique identifier that embeds a millisecond-precision Unix timestamp followed by random data, so generated UUIDs sort in chronological order.