View Source mix docs (ExDoc v0.32.1)

Uses ExDoc to generate a static web page from the project documentation.

Command line options

  • --canonical, -n - Indicate the preferred URL with rel="canonical" link element, defaults to no canonical path

  • --formatter, -f - Which formatters to use, html or epub. This option can be given more than once. By default, both html and epub are generated.

  • --language - Specifies the language to annotate the EPUB output in valid BCP 47

  • --open - open browser window pointed to the documentation

  • --output, -o - Output directory for the generated docs, default: "doc"

  • --proglang - Chooses the main programming language: elixir or erlang

The command line options have higher precedence than the options specified in your mix.exs file below.


ExDoc will automatically pull in information from your project, like the application and version. However, you may want to set :name, :source_url and :homepage_url to have a nicer output from ExDoc, for example:

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

    # Docs
    name: "My App",
    source_url: "",
    homepage_url: "http://YOUR_PROJECT_HOMEPAGE",
    docs: [
      main: "MyApp", # The main page in the docs
      logo: "path/to/logo.png",
      extras: [""]

ExDoc also allows configuration specific to the documentation to be set. The following options should be put under the :docs key in your project's main configuration. The :docs options should be a keyword list or a function returning a keyword list that will be lazily executed.

  • :annotations_for_docs - a function that receives metadata and returns a list of annotations to be added to the signature. The metadata received will also contain :module, :name, :arity and :kind to help identify which entity is currently being processed.

  • :api_reference - Whether to generate api-reference.html; default: true. If this is set to false, :main must also be set.

  • :assets - Path to a directory that will be copied as is to the "assets" directory in the output path. Its entries may be referenced in your docs under "assets/ASSET.EXTENSION"; defaults to no assets directory.

  • :authors - List of authors for the generated docs or epub.

  • :before_closing_body_tag - a function that takes as argument an atom specifying the formatter being used (:html or :epub) and returns a literal HTML string to be included just before the closing body tag (</body>). The atom given as argument can be used to include different content in both formats. Useful to inject custom assets, such as Javascript.

  • :before_closing_head_tag - a function that takes as argument an atom specifying the formatter being used (:html or :epub) and returns a literal HTML string to be included just before the closing head tag (</head>). The atom given as argument can be used to include different content in both formats. Useful to inject custom assets, such as CSS stylesheets.

  • :before_closing_footer_tag - a function that takes as argument an atom specifying the formatter being used (:html) and returns a literal HTML string to be included just before the closing footer tag (</footer>). This option only has effect on the html formatter. Useful if you want to inject an extra footer into the documentation.

  • :canonical - String that defines the preferred URL with the rel="canonical" element; defaults to no canonical path.

  • :cover - Path to the epub cover image (only PNG or JPEG accepted) The image size should be around 1600x2400. When specified, the cover will be placed under the "assets" directory in the output path under the name "cover" and the appropriate extension. This option has no effect when using the "html" formatter.

  • :deps - A keyword list application names and their documentation URL. ExDoc will by default include all dependencies and assume they are hosted on HexDocs. This can be overridden by your own values. Example: [plug: "https://myserver/plug/"]

  • :extra_section - String that defines the section title of the additional Markdown and plain text pages; default: "PAGES". Example: "GUIDES"

  • :extras - List of paths to additional Markdown (.md extension), Live Markdown (.livemd extension), Cheatsheets (.cheatmd extension) and plain text pages to add to the documentation. You can also specify keyword pairs to customize the generated filename, title and source file of each extra page; default: []. Example: ["", "LICENSE", "": [filename: "contributing", title: "Contributing", source: "CONTRIBUTING.mdx"]]

  • :filter_modules - Include only modules that match the given value. The value can be a regex, a string (representing a regex), or a two-arity function that receives the module and its metadata and returns true if the module must be included. If a string or a regex is given, it will be matched against the complete module name (which includes the "Elixir." prefix for Elixir modules). If a module has @moduledoc false, then it is always excluded.

  • :formatters - Formatter to use; default: ["html", "epub"], options: "html", "epub".

  • :groups_for_extras, :groups_for_modules, :groups_for_docs - See the "Groups" section

  • :ignore_apps - Apps to be ignored when generating documentation in an umbrella project. Receives a list of atoms. Example: [:first_app, :second_app].

  • :language - Identify the primary language of the documents, its value must be a valid BCP 47 language tag; default: "en"

  • :logo - Path to a logo image file for the project. Must be PNG, JPEG or SVG. When specified, the image file will be placed in the output "assets" directory, named "logo.EXTENSION". The image will be shown within a 48x48px area. If using SVG, ensure appropriate width, height and viewBox attributes are present in order to ensure predictable sizing and cropping.

  • :main - Main page of the documentation. It may be a module or a generated page, like "Plug" or "api-reference"; default: "api-reference".

  • :markdown_processor - The markdown processor to use, either module() or {module(), keyword()} to provide configuration options;

  • :meta - A keyword list or a map to specify meta tag attributes

  • :nest_modules_by_prefix - See the "Nesting" section

  • :output - Output directory for the generated docs; default: "doc". May be overridden by command line argument.

  • :skip_undefined_reference_warnings_on - ExDoc warns when it can't create a reference in the current project docs e.g. because of a typo. This list controls where to skip the warnings, for a given module/function/callback/type (e.g.: ["Foo", "Bar.baz/0"]) or on a given file (e.g.: ["pages/"]). This option can also be a function from a reference string to a boolean (e.g.: &String.match?(&1, ~r/Foo/)); default is nothing to be skipped.

  • :skip_code_autolink_to - Similar to :skip_undefined_reference_warnings_on, this option controls which terms will be skipped by ExDoc when building documentation. Useful for example if you want to highlight private modules or functions without warnings. This option can be a function from a term to a boolean (e.g.: &String.match?(&1, ~r/PrivateModule/)) or a list of terms (e.g.:["PrivateModule", "PrivateModule.func/1"]); default is nothing to be skipped.

  • :source_beam - Path to the beam directory; default: mix's compile path.

  • :source_ref - The branch/commit/tag used for source link inference; default: "main".

  • :source_url_pattern - Public URL of the project for source links. This is derived automatically from the project's :source_url and :source_ref when using one of the supported public hosting services (currently GitHub, GitLab, or Bitbucket). If you are using one of those services with their default public hostname, you do not need to set this configuration.

    However, if using a different solution, or self-hosting, you will need to set this configuration variable to a pattern for source code links. The value must be a string or a function.

    If a string, then it should be the full URI to use for links with the following variables available for interpolation:

    • %{path}: the path of a file in the repo
    • %{line}: the line number in the file

    For GitLab/GitHub:{path}#L%{line}

    For Bitbucket:{path}#cl-%{line}

    If a function, then it must be a function that takes two arguments, path and line, where path is either an relative path from the cwd, or an absolute path. The function must return the full URI as it should be placed in the documentation.


ExDoc content can be organized in groups. This is done via the :groups_for_extras and :groups_for_modules. For example, imagine you are storing extra guides in your documentation which are organized per directory. In the extras section you have:

extras: [



You can have those grouped as follows:

groups_for_extras: [
  "Introduction": Path.wildcard("guides/introduction/*.md"),
  "Advanced": Path.wildcard("guides/advanced/*.md")

Or via a regex:

groups_for_extras: [
  "Introduction": ~r"/introduction/",
  "Advanced": ~r"/advanced/"

Similar can be done for modules:

groups_for_modules: [
  "Data types": [Atom, Regex, URI],
  "Collections": [Enum, MapSet, Stream]

A regex or the string name of the module is also supported.

Grouping functions and callbacks

Functions and callbacks inside a module can also be organized in groups. This is done via the :groups_for_docs configuration which is a keyword list of group titles and filtering functions that receive the documentation metadata of functions as argument. The metadata received will also contain :module, :name, :arity and :kind to help identify which entity is currently being processed.

For example, imagine that you have an API client library with a large surface area for all the API endpoints you need to support. It would be helpful to group the functions with similar responsibilities together. In this case in your module you might have:

defmodule APIClient do
  @doc section: :auth
  def refresh_token(params \\ [])

  @doc subject: :object
  def update_status(id, new_status)

  @doc permission: :grant
  def grant_privilege(resource, privilege)

And then in the configuration you can group these with:

groups_for_docs: [
  Authentication: & &1[:section] == :auth,
  Resource: & &1[:subject] == :object,
  Admin: & &1[:permission] in [:grant, :write]

A function can belong to a single group only. If multiple group filters match, the first will take precedence. Functions and callbacks that don't have a custom group will be listed under the default "Functions" and "Callbacks" group respectively.

Meta-tags configuration

It is also possible to configure some of ExDoc behaviour using meta tags. These meta tags can be inserted using before_closing_head_tag.

  • exdoc:autocomplete - when set to "off", it disables autocompletion.

  • exdoc:full-text-search-url - the URL to use when performing full text search. The search string will be prepended to the URL as a parameter. It defaults to ExDoc's auto-generated search page.


ExDoc also allows module names in the sidebar to appear nested under a given prefix. The :nest_modules_by_prefix expects a list of module names, such as [Foo.Bar, Bar.Baz]. In this case, a module named Foo.Bar.Baz will appear nested within Foo.Bar and only the name Baz will be shown in the sidebar. Note the Foo.Bar module itself is not affected.

This option is mainly intended to improve the display of long module names in the sidebar, particularly when they are too long for the sidebar or when many modules share a long prefix. If you mean to group modules logically or call attention to them in the docs, you should probably use :groups_for_modules (which can be used in conjunction with :nest_modules_by_prefix).

Umbrella project

ExDoc can be used in an umbrella project and generates a single documentation for all child apps. You can use the :ignore_apps configuration to exclude certain projects in the umbrella from documentation.

Generating documentation per each child app can be achieved by running:

mix cmd mix docs

See mix help cmd for more information.