ExDoc

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ExDoc is a tool to generate documentation for your Elixir projects. To see an example, you can access Elixir’s official docs.

To learn about how to document your projects, see Elixir’s writing documentation page.

To see all supported options, see the documentation for mix docs.

Features

ExDoc ships with many features:

Usage

You can use ExDoc with Mix (recommended for Elixir projects), with Rebar (recommended for Erlang projects), or via the command line.

Using ExDoc with Mix

ExDoc requires Elixir v1.10 or later.

First, add ExDoc as a dependency:

def deps do
  [
    {:ex_doc, "~> 0.27", only: :dev, runtime: false},
  ]
end

Then run mix deps.get.

Erlang development environment

Some Operating System distributions split Erlang into multiple packages, and at least one ExDoc dependency (earmark_parser) requires the Erlang development environment. If you see a message like “/usr/lib/erlang/lib/parsetools-2.3.1/include/yeccpre.hrl: no such file or directory”, it means you lack this environment. For instance, on the Debian operating system and its derivatives, you need to apt install erlang-dev.

ExDoc will automatically pull in information from your projects, such as the application and version. However, you may want to set :name, :source_url and :homepage_url in order to have nicer output from ExDoc:

def project do
  [
    app: :my_app,
    version: "0.1.0-dev",
    deps: deps(),

    # Docs
    name: "MyApp",
    source_url: "https://github.com/USER/PROJECT",
    homepage_url: "http://YOUR_PROJECT_HOMEPAGE",
    docs: [
      main: "MyApp", # The main page in the docs
      logo: "path/to/logo.png",
      extras: ["README.md"]
    ]
  ]
end

Now you are ready to generate your project documentation with mix docs. To see all options available, run mix help docs.

Using ExDoc with Rebar3

From Erlang/OTP 24+, you can use ExDoc to render your Erlang documentation written with EDoc. See rebar3_ex_doc for more information.

Using ExDoc via command line

You can use ExDoc via the command line.

  1. Install ExDoc as an escript: 

    $ mix escript.install hex ex_doc

  2. Now you are ready to use it in your projects. Move into your project directory and make sure it’s compiled: 

    $ cd PATH_TO_YOUR_PROJECT
$ mix compile

  3. Invoke the ex_doc executable from your project: 

    $ ex_doc "PROJECT_NAME" "PROJECT_VERSION" _build/dev/lib/project/ebin -m "PROJECT_MODULE" -u "https://github.com/GITHUB_USER/GITHUB_REPO" -l path/to/logo.png

    Examples of appropriate values: 

    PROJECT_NAME    => Ecto
PROJECT_VERSION => 0.1.0
PROJECT_MODULE  => Ecto (the main module provided by the library)
GITHUB_USER     => elixir-lang
GITHUB_REPO     => ecto

Syntax highlighting

ExDoc uses the makeup project for syntax highlighting. By default, highlighters for Erlang and Elixir are included. To syntax-highlight other languages, simply add the equivalent makeup_LANGUAGE package to your mix.exs/rebar.config file. For example, for HTML support you would add:

{:makeup_html, ">= 0.0.0", only: :dev, runtime: false}

You can find all supported languages under the Makeup organization on GitHub and view them at Makeup’s website.

Additional pages

You can publish additional pages in your project documentation by configuring them as :extras. The following formats and extensions are supported:

For example, you can set your :extras to:

extras: ["README.md", "LICENSE", "tutorial.livemd", "cheatsheet.cheatmd"]

Run mix help docs for more information on configuration.

Metadata

ExDoc supports metadata keys in your documentation.

In Elixir, you can add metadata to modules and functions.

For a module, use @moduledoc, which is equivalent to adding the annotation to everything inside the module (functions, macros, callbacks, types):

@moduledoc since: "1.10.0"

For a function, use @doc:

@doc since: "1.13.1"

In Erlang’s EDoc:

%% @since 0.1.0

The following metadata is available for both modules and functions:

The following metadata is available for modules:

Auto-linking

ExDoc for Elixir will automatically generate links across modules and functions if you enclose them in backticks.

ExDoc supports linking to modules (`MyModule`), functions (`MyModule.function/1`), types (`t:MyModule.type/2`) and callbacks (`c:MyModule.callback/3`). If you want to link a function, type or callback in the current module, you may skip the module name; e.g.: `function/1`.

You can also use custom text; e.g.: [custom text](`MyModule.function/1`). This also allows you to refer to OTP modules; e.g.: [`:array`](`:array`).

Link to extra pages using the syntax [Up and running](Up and running.md), skipping the directory in which the page is. The final link will be automatically converted to up-and-running.html.

Admonition blocks

You may want to draw attention to certain statements by taking them out of the content’s flow and labeling them with a priority. Such statements are called admonitions. (They are also known as asides or callouts.) An admonition block is rendered based on the assigned label or class. ExDoc supports warning, error, info, tip and neutral tags, on header levels h3 and h4.

The syntax is as follows:

> #### Error {: .error}
>
> This syntax will render an error block

The result for the previous syntax is:

Error

This syntax will render an error block

For example, if you change the class name to neutral, you get the same admonition block in neutral style:

Neutral

This syntax will render a neutral block

Tabsets

Where only one section of content of a series is likely to apply to the reader, you may wish to define a set of tabs.

This example contains code blocks, separating them into tabs based on language:

Elixir

IO.puts "Hello, world!"

Erlang

io:fwrite("Hello, world!\n").

and<!– tabs-close –>HTML comments. Eachh3heading results in a new tab panel, with its text setting the tab button label. Here is the above example's source: ````markdown <!-- tabs-open --> ### Elixir ```elixir IO.puts "Hello, world!" ``` ### Erlang ```erlang io:fwrite("hello, world!\n"). ``` <!-- tabs-close --> ```` ## Extensions ExDoc renders Markdown content for you, but you can extend it to render complex objects on the page using JavaScript. To inject custom JavaScript into every page, add this to your configuration: ```elixir docs: [ # ... before_closing_head_tag: &before_closing_head_tag/1, before_closing_body_tag: &before_closing_body_tag/1 ] # ... defp before_closing_head_tag(:html) do """ <!-- HTML injected at the end of the <head> element --> """ end defp before_closing_head_tag(:epub), do: "" defp before_closing_body_tag(:html) do """ <!-- HTML injected at the end of the <body> element --> """ end defp before_closing_body_tag(:epub), do: "" ``` Besides an anonymous function, you can also pass amodule-function-argstuple. It will the given module and function, with the format prefixed to the arguments: ```elixir docs: [ # ... before_closing_head_tag: {MyModule, :before_closing_head_tag, []}, before_closing_body_tag: {MyModule, :before_closing_body_tag, []} ] ``` Or you can pass a map where the key is the format: ```elixir docs: [ # ... before_closing_head_tag: %{html: "...", epub: "..."}, before_closing_body_tag: %{html: "...", epub: "..."} ] ``` ### Rendering Math If you write TeX-style math in your Markdown, such as$\sum_{i}^{N} x_i$, it ends up as raw text on the generated pages. To render expressions, we recommend using [KaTeX](https://katex.org/), a JavaScript library that turns expressions into graphics. To load and trigger KaTeX on every documentation page, we can insert the following HTML: ```html <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.css" integrity="sha384-vKruj+a13U8yHIkAyGgK1J3ArTLzrFGBbBc0tDp4ad/EyewESeXE/Iv67Aj8gKZ0" crossorigin="anonymous"> <script defer src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/katex.min.js" integrity="sha384-PwRUT/YqbnEjkZO0zZxNqcxACrXe+j766U2amXcgMg5457rve2Y7I6ZJSm2A0mS4" crossorigin="anonymous"></script> <link href="https://cdn.jsdelivr.net/npm/katex-copytex@1.0.2/dist/katex-copytex.min.css" rel="stylesheet" type="text/css"> <script src="https://cdn.jsdelivr.net/npm/katex-copytex@1.0.2/dist/katex-copytex.min.js" crossorigin="anonymous"></script> <script defer src="https://cdn.jsdelivr.net/npm/katex@0.16.4/dist/contrib/auto-render.min.js" integrity="sha384-+VBxd3r6XgURycqtZ117nYw44OOcIax56Z4dCRWbxyPt0Koah1uHoK0o4+/RRE05" crossorigin="anonymous" onload="renderMathInElement(document.body, { delimiters: [ {left: '$$', right: '$$', display: true}, {left: '$', right: '$', display: false}, ] });"></script> </script> ``` For more details and configuration options, see the [KaTeX Auto-render Extension](https://katex.org/docs/autorender.html). ### Rendering Vega-Lite plots Snippets are also objects you may want to render in a special manner. For example, assuming your Markdown includes Vega-Lite specification invega-litecode snippets: ```html <script src="https://cdn.jsdelivr.net/npm/vega@5.20.2"></script> <script src="https://cdn.jsdelivr.net/npm/vega-lite@5.1.1"></script> <script src="https://cdn.jsdelivr.net/npm/vega-embed@6.18.2"></script> <script> document.addEventListener("DOMContentLoaded", function () { for (const codeEl of document.querySelectorAll("pre code.vega-lite")) { try { const preEl = codeEl.parentElement; const spec = JSON.parse(codeEl.textContent); const plotEl = document.createElement("div"); preEl.insertAdjacentElement("afterend", plotEl); vegaEmbed(plotEl, spec); preEl.remove(); } catch (error) { console.log("Failed to render Vega-Lite plot: " + error) } } }); </script> ``` For more details and configuration options, see [vega/vega-embed](https://github.com/vega/vega-embed). ### Rendering Mermaid graphs Similarly to the example above, if your Markdown includes Mermaid graph specification inmermaidcode snippets: ```html <script src="https://cdn.jsdelivr.net/npm/mermaid@10.2.3/dist/mermaid.min.js"></script> <script> document.addEventListener("DOMContentLoaded", function () { mermaid.initialize({ startOnLoad: false, theme: document.body.className.includes("dark") ? "dark" : "default" }); let id = 0; for (const codeEl of document.querySelectorAll("pre code.mermaid")) { const preEl = codeEl.parentElement; const graphDefinition = codeEl.textContent; const graphEl = document.createElement("div"); const graphId = "mermaid-graph-" + id++; mermaid.render(graphId, graphDefinition).then(({svg, bindFunctions}) => { graphEl.innerHTML = svg; bindFunctions?.(graphEl); preEl.insertAdjacentElement("afterend", graphEl); preEl.remove(); }); } }); </script> ``` For more details and configuration options, see the [Mermaid usage docs](https://mermaid-js.github.io/mermaid/#/usage). ## Contributing The easiest way to test changes to ExDoc is to locally rebuild the app and its own documentation: 1. Runmix setupto install all dependencies. 2. Runmix buildto generate the docs. This is a custom alias that will build assets, recompile ExDoc, and output fresh docs into thedoc/directory. 3. If working on the assets, you may wish to run the assets build script in watch mode:npm run –prefix assets build:watch. 4. Runmix lintto check if the Elixir and JavaScript files are properly formatted. You can runmix fixto let the JavaScript linter and Elixir formatter fix the code automatically before submitting your pull request. 5. Please do not add the files generated in theformatters/directory to your commits. These will be handled as necessary by the repository maintainers. See the README in theassets/` directory for more information on working on the assets. ## License ExDoc source code is released under the Apache 2 License. The generated contents, however, are under different licenses based on projects used to help render HTML, including CSS, JS, and other assets. Any documentation generated by ExDoc, or any documentation generated by any “Derivative Works” (as specified in the Apache 2 License), must include a direct, readable, and visible link to the ExDoc repository on each rendered material. For HTML pages, every single page is a rendered material. For PDF, EPUB and other ebook formats, the whole body of documentation is a rendered material.