OPC UA (Open Platform Communications Unified Architecture) is a modern industrial communication standard maintained by the OPC Foundation. It is the successor to the original OPC standard, redesigned to be platform-independent, securely encrypted by default, and capable of handling complex data models rather than simple register reads.

In short: OPC UA is the dominant standard for Industry 4.0 and modern industrial interoperability. It is supported by major automation vendors (Siemens, Rockwell, ABB, Schneider Electric, Mitsubishi, Beckhoff) and is increasingly built directly into PLCs and edge devices. It supports both client-server and publish-subscribe communication patterns, runs over TCP/IP or MQTT, and includes built-in authentication and encryption.

The difference between OPC UA and Modbus is one of architecture, not just modernity. Modbus exposes raw registers and trusts the integrator to interpret them. OPC UA exposes a structured information model where data is named, typed, and described. A temperature reading in OPC UA includes its unit, range, quality status, and timestamp; a Modbus register is just a number that has to be interpreted by reference to an external document.

For IIoT deployments, OPC UA is increasingly the protocol of choice for new builds. Many Teltonika routers support OPC UA client functionality, allowing them to read data from OPC UA servers on the plant network and forward it to cloud platforms via MQTT. Existing Modbus equipment can be bridged into OPC UA infrastructure where needed, giving a migration path rather than a forklift upgrade.