A UUID (Universally Unique Identifier), on Windows also called GUID, is a 128-bit value that is practically unique without central coordination. UUIDs are used as primary keys in databases, for object and session IDs, in APIs and anywhere unique identifiers are needed without collision risk.
Version 4 is almost entirely random. Version 7 prepends a timestamp and is therefore time-sortable – improving database index performance over purely random UUIDs. Generation runs entirely in your browser via the cryptographically secure Web Crypto API; no data is transmitted or stored.