Installation

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Prerequisites

This library requires Elixir 1.15+ and Erlang/OTP 26+.

While it is possible to use this library with the service run by W3C at validator.w3.org/nu, I would recommend running your own instance. You will eliminate a lot of network latency if it runs on the same machine as your code, and you will not hit any rate limits that might exist for validator.w3.org/nu.

The source of the Checker can be found in the repository validator/validator. Follow their instructions on how to download it and run it as a web server.

The easiest option is to use the Docker image, like this:

docker run -it --rm -p 8888:8888 ghcr.io/validator/validator:latest

The command might require an additional --platform linux/amd64 flag on M1 macs.

Check if the server is running:

$ curl localhost:8888 -I
HTTP/1.1 200 OK

Installation

Make sure to read about the prerequisites first.

Add Vnu as a dependency to your project's mix.exs.

defp deps do
  [
    {:vnu, "~> 1.2", only: [:dev, :test]}
  ]
end

And run:

$ mix deps.get

The built-in HTTP client adapter uses :httpc, which ships with Erlang/OTP. If you don't want to use :httpc, you can implement your own HTTP client module using the Vnu.HTTPClient behavior and pass it in the http_client option.