globally unique identifier (GUID-globally unique identifier), GUID is a 128-bit globallyly unique identifier (GUID - Globally Unique Identifier), GUID is a 128-bit binary number (16 bytes) that can be used for all computers and networks that require a unique identifier. It is very unlikely that this identifier will be repeated. GUIDs are in the format "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", where each x is a hexadecimal number in the range 0-9 or a-f.