Configuring Renderers

Renderers (also called “backends”) are responsible for creating the output of the book.

The following backends are built-in:

  • html — This renders the book to HTML. This is enabled by default if no other [output] tables are defined in book.toml.
  • markdown — This outputs the book as markdown after running the preprocessors. This is useful for debugging preprocessors.

The community has developed several backends. See the Third Party Plugins wiki page for a list of available backends.

For information on how to create a new backend, see the Backends for Developers chapter.

Output tables

Backends can be added by including a output table in book.toml with the name of the backend. For example, if you have a backend called mdbook-wordcount, then you can include it with:


With this table, mdBook will execute the mdbook-wordcount backend.

This table can include additional key-value pairs that are specific to the backend. For example, if our example backend needed some extra configuration options:

ignores = ["Example Chapter"]

If you define any [output] tables, then the html backend is not enabled by default. If you want to keep the html backend running, then just include it in the book.toml file. For example:

title = "My Awesome Book"



If more than one output table is included, this changes the behavior for the layout of the output directory. If there is only one backend, then it places its output directly in the book directory (see to override this location). If there is more than one backend, then each backend is placed in a separate directory underneath book. For example, the above would have directories book/html and book/wordcount.

Custom backend commands

By default when you add an [] table to your book.toml file, mdbook will try to invoke the mdbook-foo executable. If you want to use a different program name or pass in command-line arguments, this behaviour can be overridden by adding a command field.

command = "python"

Optional backends

If you enable a backend that isn’t installed, the default behavior is to throw an error. This behavior can be changed by marking the backend as optional:

optional = true

This demotes the error to a warning.

HTML renderer options

The HTML renderer has a variety of options detailed below. They should be specified in the [output.html] table of the book.toml file.

# Example book.toml file with all output options.
title = "Example book"
authors = ["John Doe", "Jane Doe"]
description = "The example book covers examples."

theme = "my-theme"
default-theme = "light"
preferred-dark-theme = "navy"
smart-punctuation = true
mathjax-support = false
copy-fonts = true
additional-css = ["custom.css", "custom2.css"]
additional-js = ["custom.js"]
no-section-label = false
git-repository-url = ""
git-repository-icon = "fa-github"
edit-url-template = "{path}"
site-url = "/example-book/"
cname = ""
input-404 = ""

The following configuration options are available:

  • theme: mdBook comes with a default theme and all the resource files needed for it. But if this option is set, mdBook will selectively overwrite the theme files with the ones found in the specified folder.
  • default-theme: The theme color scheme to select by default in the ‘Change Theme’ dropdown. Defaults to light.
  • preferred-dark-theme: The default dark theme. This theme will be used if the browser requests the dark version of the site via the prefers-color-scheme CSS media query. Defaults to navy.
  • smart-punctuation: Converts quotes to curly quotes, ... to , -- to en-dash, and --- to em-dash. See [Smart Punctuation]. Defaults to false.
  • curly-quotes: Deprecated alias for smart-punctuation.
  • mathjax-support: Adds support for MathJax. Defaults to false.
  • copy-fonts: (Deprecated) If true (the default), mdBook uses its built-in fonts which are copied to the output directory. If false, the built-in fonts will not be used. This option is deprecated. If you want to define your own custom fonts, create a theme/fonts/fonts.css file and store the fonts in the theme/fonts/ directory.
  • google-analytics: This field has been deprecated and will be removed in a future release. Use the theme/head.hbs file to add the appropriate Google Analytics code instead.
  • additional-css: If you need to slightly change the appearance of your book without overwriting the whole style, you can specify a set of stylesheets that will be loaded after the default ones where you can surgically change the style.
  • additional-js: If you need to add some behaviour to your book without removing the current behaviour, you can specify a set of JavaScript files that will be loaded alongside the default one.
  • no-section-label: mdBook by defaults adds numeric section labels in the table of contents column. For example, “1.”, “2.1”. Set this option to true to disable those labels. Defaults to false.
  • git-repository-url: A url to the git repository for the book. If provided an icon link will be output in the menu bar of the book.
  • git-repository-icon: The FontAwesome icon class to use for the git repository link. Defaults to fa-github which looks like . If you are not using GitHub, another option to consider is fa-code-fork which looks like .
  • edit-url-template: Edit url template, when provided shows a “Suggest an edit” button (which looks like ) for directly jumping to editing the currently viewed page. For e.g. GitHub projects set this to<owner>/<repo>/edit/<branch>/{path} or for Bitbucket projects set it to<owner>/<repo>/src/<branch>/{path}?mode=edit where {path} will be replaced with the full path of the file in the repository.
  • input-404: The name of the markdown file used for missing files. The corresponding output file will be the same, with the extension replaced with html. Defaults to
  • site-url: The url where the book will be hosted. This is required to ensure navigation links and script/css imports in the 404 file work correctly, even when accessing urls in subdirectories. Defaults to /. If site-url is set, make sure to use document relative links for your assets, meaning they should not start with /.
  • cname: The DNS subdomain or apex domain at which your book will be hosted. This string will be written to a file named CNAME in the root of your site, as required by GitHub Pages (see Managing a custom domain for your GitHub Pages site).


The [output.html.print] table provides options for controlling the printable output. By default, mdBook will include an icon on the top right of the book (which looks like ) that will print the book as a single page.

enable = true    # include support for printable output
page-break = true # insert page-break after each chapter
  • enable: Enable print support. When false, all print support will not be rendered. Defaults to true.
  • page-break: Insert page breaks between chapters. Defaults to true.


The [output.html.fold] table provides options for controlling folding of the chapter listing in the navigation sidebar.

enable = false    # whether or not to enable section folding
level = 0         # the depth to start folding
  • enable: Enable section-folding. When off, all folds are open. Defaults to false.
  • level: The higher the more folded regions are open. When level is 0, all folds are closed. Defaults to 0.


The [output.html.playground] table provides options for controlling Rust sample code blocks, and their integration with the Rust Playground.

editable = false         # allows editing the source code
copyable = true          # include the copy button for copying code snippets
copy-js = true           # includes the JavaScript for the code editor
line-numbers = false     # displays line numbers for editable code
runnable = true          # displays a run button for rust code
  • editable: Allow editing the source code. Defaults to false.
  • copyable: Display the copy button on code snippets. Defaults to true.
  • copy-js: Copy JavaScript files for the editor to the output directory. Defaults to true.
  • line-numbers: Display line numbers on editable sections of code. Requires both editable and copy-js to be true. Defaults to false.
  • runnable: Displays a run button for rust code snippets. Changing this to false will disable the run in playground feature globally. Defaults to true.


The [output.html.code] table provides options for controlling code blocks.

# A prefix string per language (one or more chars).
# Any line starting with whitespace+prefix is hidden.
hidelines = { python = "~" }
  • hidelines: A table that defines how hidden code lines work for each language. The key is the language and the value is a string that will cause code lines starting with that prefix to be hidden.


The [] table provides options for controlling the built-in text search. mdBook must be compiled with the search feature enabled (on by default).

enable = true            # enables the search feature
limit-results = 30       # maximum number of search results
teaser-word-count = 30   # number of words used for a search result teaser
use-boolean-and = true   # multiple search terms must all match
boost-title = 2          # ranking boost factor for matches in headers
boost-hierarchy = 1      # ranking boost factor for matches in page names
boost-paragraph = 1      # ranking boost factor for matches in text
expand = true            # partial words will match longer terms
heading-split-level = 3  # link results to heading levels
copy-js = true           # include Javascript code for search
  • enable: Enables the search feature. Defaults to true.
  • limit-results: The maximum number of search results. Defaults to 30.
  • teaser-word-count: The number of words used for a search result teaser. Defaults to 30.
  • use-boolean-and: Define the logical link between multiple search words. If true, all search words must appear in each result. Defaults to false.
  • boost-title: Boost factor for the search result score if a search word appears in the header. Defaults to 2.
  • boost-hierarchy: Boost factor for the search result score if a search word appears in the hierarchy. The hierarchy contains all titles of the parent documents and all parent headings. Defaults to 1.
  • boost-paragraph: Boost factor for the search result score if a search word appears in the text. Defaults to 1.
  • expand: True if search should match longer results e.g. search micro should match microwave. Defaults to true.
  • heading-split-level: Search results will link to a section of the document which contains the result. Documents are split into sections by headings this level or less. Defaults to 3. (### This is a level 3 heading)
  • copy-js: Copy JavaScript files for the search implementation to the output directory. Defaults to true.


The [output.html.redirect] table provides a way to add redirects. This is useful when you move, rename, or remove a page to ensure that links to the old URL will go to the new location.

"/appendices/bibliography.html" = ""
"/other-installation-methods.html" = "../infra/other-installation-methods.html"

The table contains key-value pairs where the key is where the redirect file needs to be created, as an absolute path from the build directory, (e.g. /appendices/bibliography.html). The value can be any valid URI the browser should navigate to (e.g., /overview.html, or ../bibliography.html).

This will generate an HTML page which will automatically redirect to the given location. Note that the source location does not support # anchor redirects.

Markdown Renderer

The Markdown renderer will run preprocessors and then output the resulting Markdown. This is mostly useful for debugging preprocessors, especially in conjunction with mdbook test to see the Markdown that mdbook is passing to rustdoc.

The Markdown renderer is included with mdbook but disabled by default. Enable it by adding an empty table to your book.toml as follows:


There are no configuration options for the Markdown renderer at this time; only whether it is enabled or disabled.

See the preprocessors documentation for how to specify which preprocessors should run before the Markdown renderer.