cONNXr

The cONNXr project provides a pure C runtime for ONNX models intended for embedded devices.

github.com/alrevuelta/cONNXr
cONNXr homepage screenshot

About cONNXr

cONNXr is a runtime for running inference on ONNX machine learning models. It is written in pure C99 with no external dependencies and is aimed at embedded devices and older hardware that cannot compile newer C or C++ code. Models can be trained in any framework that exports to ONNX, such as TensorFlow, Keras, or scikit-learn, and then run with this runtime.

The runtime uses single-threaded C99 code and has no GPU or hardware accelerator support. Several models are supported out of the box, including MNIST, tiny YOLO v2, super resolution, and MobileNet v2. A model that uses an operator the project has not yet implemented will not run. The project describes itself as at a very early stage and not production ready, and it is looking for developers to contribute. Linking it as a static library is not yet supported.

Key features

  • Pure C99 ONNX runtime with no external dependencies
  • Runs inference on ONNX models exported from frameworks such as TensorFlow, Keras, and scikit-learn
  • Command-line runner that takes an ONNX model and a .pb input file
  • Example C code showing how to resolve operators and run inference
  • Architecture that allows operators to be replaced for bare-metal hardware with dedicated accelerators
  • Out-of-the-box support for MNIST, tiny YOLO v2, super resolution, and MobileNet v2 models
Best for: Developers who need to run ONNX model inference on embedded or older hardware that cannot build newer C++ code.
Good for
  • Has zero dependencies and is written in pure C99
  • Works with models trained in any framework that exports to ONNX
Watch out for
  • Described by the project as at a very early stage and not production ready
  • Has no GPU or hardware accelerator support and uses non-multi-threaded code
  • Models that use operators not yet implemented will not work

cONNXr at a glance

Type
Open-source project
Pricing
Not confirmed. Check the site
Open source
Yes · Source code
Language
English
Last checked
Oct 6, 2026 · Online when checked
Listed
Oct 5, 2026

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cONNXr FAQ

Does cONNXr support GPUs or hardware accelerators?
No. The project states that it has no GPUs or hardware accelerators and uses only pure, non-multi-thread C99 code.
Why might my ONNX model fail to run?
The project says a model that does not work is probably using an operator that has not been implemented yet. Users are invited to open an issue.
Can cONNXr be used as a static library?
Not yet. The project says linking it as a static library is not supported at this time, so the source files must be included and compiled in your project.
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