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An open source and free C (C99) OPC UA stack licensed under LGPL + static linking exception.

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Latest stable release

Demo server and client downloads:


  • stack design based solely on IEC 62541
  • licensed under open source (LGPL & static linking exception)
  • royalty free, available on GitHub


  • single or multi-threaded architecture
  • one thread per connection/session



  • written in C99 with POSIX support
  • compiled server is smaller than 100kb
  • runs on Windows (x86, x64), Linux (x86, x64, ARM e.g. Raspberry Pi, SPARCstation), QNX and Android


  • dynamically loadable and reconfigurable user models

More info?

A full list of supported OPC UA features can be found here: open62541 features.
You can also dig into the documentation, check the bugtracker or read the whitepaper (coming soon)

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