The JSON message mapping uses the OPC UA JSON encoding defined in OPC 10000-6. If an ExtensionObject is encoded, the TypeId shall be the DataType NodeId of the contained structure.

JSON is a format that uses human readable text. It is defined in IETF RFC 8259.

The JSON based message mapping allows OPC UA Applications to interoperate with web and enterprise software that use this format and do not understand OPC UA specific encodings.

The JSON message mapping defines different optional header fields, variations of field settings and different message types. Available layouts with standard settings and the corresponding URI Strings for JSON are defined in A.3.