Fork me on GitHub

open62541 is an open source C (C99) implementation of OPC UA licensed under the Mozilla Public License v2.0.


  • Based solely on IEC 62541
  • Open source license (Mozilla Public License v2.0)
  • Royalty free, available on GitHub


  • Written in C99 with architecture-specific plugins (POSIX, ...)
  • Runs on Windows, Linux, QNX, Android and diverse embedded systems
  • Compiled server can be smaller than 100kb


  • Event-based architecture
  • Single or multi-threaded


  • Information model can be modified at runtime
  • Generation of data types and information models from XML specification files


April 2019: Realtime OPC UA PubSub Publisher released

At Hannover Fair 2019, we demonstrated the open62541 Realtime OPC UA PubSub Publisher at the booth of the OPC Foundation. The code is now released on Github as well.

The measurements can be replicated on RTOS and Linux (with the RT-Preempt patches) environments. The example code can be found here.

This video on the demonstrator from Hannover Fair explains the approach behind:

June 2018: Measurements for OPC UA PubSub over TSN

Our commercial partner Kalycito is publishing latency and jitter measurements for OPC UA PubSub over TSN based on open6251. Click here to know more for full details.

Mai 2018: PubSub Support

Support for the new OPC UA PubSub Extension (Part 14) based on UDP/multicast has landed on the master branch.


Latest release:


Companies contributing to open62541

Commercial support offerings for open62541