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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, VxWorks, 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


February 2021: New release open6251 v1.2

See the release page for more information:

January 2021: Quick start guide of OPC UA PubSub with enhanced user experience

Our commercial partner Kalycito has enhanced the out of the box user experience to setup the environment and to run the OPC UA PubSub on real-time Linux over TSN. User can now have a running sample in less than 20 minutes. Follow the quick start guide available in README file

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 open62541. Click here to know more for full details.

May 2018: PubSub Support

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


Building from source

A detailed description on how to build from source can be found here: Installing

Prebuilt packages

Prebuild binaries

You can always find prebuild binaries for every release on our Github Release Page.

Nightly single file releases for Linux and Windows of the last 50 commits can be found here:

The latest release binaries are also listed in the next section a few lines below.

OS Specific packages

Debian packages can be found in our official PPA:

To install the open62541-dev stable package in Ubuntu, use these lines:

sudo add-apt-repository ppa:open62541-team/ppa
sudo apt-get update
sudo apt-get install libopen62541-1-dev


Latest release:


Companies contributing to open62541

Commercial support offerings for open62541