IEC 62541-6:2020 is available as IEC 62541-6:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 62541-6:2020 specifies the OPC Unified Architecture (OPC UA) mapping between the security model described in IEC TR 62541-2, the abstract service definitions specified in IEC 62541-4, the data structures defined in IEC 62541-5 and the physical network protocols that can be used to implement the OPC UA specification. This third edition cancels and replaces the second edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
a) Encodings:
• added JSON encoding for PubSub (non-reversible);
• added JSON encoding for Client/Server (reversible);
• added support for optional fields in structures;
• added support for Unions.
b) Transport mappings:
• added WebSocket secure connection – WSS;
• added support for reverse connectivity;
• added support for session-less service invocation in HTTPS.
c) Deprecated Transport (missing support on most platforms):
• SOAP/HTTP with WS-SecureConversation (all encodings).
d) Added mapping for JSON Web Token.
e) Added support for Unions to NodeSet Schema.
f) Added batch operations to add/delete nodes to/from NodeSet Schema.
g) Added support for multi-dimensional arrays outside of Variants.
h) Added binary representation for Decimal data types.
i) Added mapping for an OAuth2 Authorization Framework.