Globally Unique Identifier/Universally Unique Identifier. A unique identification string used with remote procedure calls. Every interface and object class uses a GUID for identification. A GUID is a 128-bit value. For example, 12345678-1234-1234-1234-123456789ABC is a syntactically correct GUID. The GUIDs on the client and server must match for the client and server to bind. Vendors of objects can request that Microsoft allocate one or more sets of 256 GUIDs for their exclusive use. Alternatively, if you have a network card, you can run a tool named Uuidgen.exe, which provides a set of 256 GUIDs based on the time of day, the date, and a unique number contained in your network card.