HTML theme development

Added in version 0.6.

Note

This document provides information about creating your own theme. If you simply wish to use a pre-existing HTML themes, refer to HTML Theming.

Sphinx supports changing the appearance of its HTML output via themes. A theme is a collection of HTML templates, stylesheet(s) and other static files. Additionally, it has a configuration file which specifies from which theme to inherit, which highlighting style to use, and what options exist for customizing the theme’s look and feel.

Themes are meant to be project-unaware, so they can be used for different projects without change.

Note

See Sphinx Extensions API for more information that may be helpful in developing themes.

Creating themes

Themes take the form of either a directory or a zipfile (whose name is the theme name), containing the following:

  • Either a theme.toml file (preferred) or a theme.conf file.

  • HTML templates, if needed.

  • A static/ directory containing any static files that will be copied to the output static directory on build. These can be images, styles, script files.

Theme configuration (theme.toml)

The theme.toml file is a TOML document, containing two tables: [theme] and [options].

The [theme] table defines the theme’s settings:

  • inherit (string): The name of the base theme from which to inherit settings, options, templates, and static files. All static files from theme ‘ancestors’ will be used. The theme will use all options defined in inherited themes. Finally, inherited themes will be used to locate missing templates (for example, if "basic" is used as the base theme, most templates will already be defined).

    If set to "none", the theme will not inherit from any other theme. Inheritance is recursive, forming a chain of inherited themes (e.g. default -> classic -> basic -> none).

  • stylesheets (list of strings): A list of CSS filenames which will be included in generated HTML header. Setting the html_style config value will override this setting.

    Other mechanisms for including multiple stylesheets include @import in CSS or using a custom HTML template with appropriate <link rel="stylesheet"> tags.

  • sidebars (list of strings): A list of sidebar templates. This can be overridden by the user via the html_sidebars config value.

  • pygments_style (table): A TOML table defining the names of Pygments styles to use for highlighting syntax. The table has two recognised keys: default and dark. The style defined in the dark key will be used when the CSS media query (prefers-color-scheme: dark) evaluates to true.

    [theme.pygments_style.default] can be overridden by the user via the pygments_style config value.

The [options] table defines the options for the theme. It is structured such that each key-value pair corresponds to a variable name and the corresponding default value. These options can be overridden by the user in html_theme_options and are accessible from all templates as theme_<name>.

Added in version 7.3: theme.toml support.

Exemplar theme.toml file:

[theme]
inherit = "basic"
stylesheets = [
    "main-CSS-stylesheet.css",
]
sidebars = [
    "localtoc.html",
    "relations.html",
    "sourcelink.html",
    "searchbox.html",
]
# Style names from https://pygments.org/styles/
pygments_style = { default = "style_name", dark = "dark_style" }

[options]
variable = "default value"

Theme configuration (theme.conf)

The theme.conf file is in INI format [1] (readable by the standard Python configparser module) and has the following structure:

[theme]
inherit = base theme
stylesheet = main CSS name
pygments_style = stylename
sidebars = localtoc.html, relations.html, sourcelink.html, searchbox.html

[options]
variable = default value
  • The inherit setting gives the name of a “base theme”, or none. The base theme will be used to locate missing templates (most themes will not have to supply most templates if they use basic as the base theme), its options will be inherited, and all of its static files will be used as well. If you want to also inherit the stylesheet, include it via CSS’ @import in your own.

  • The stylesheet setting gives a list of CSS filenames separated commas which will be referenced in the HTML header. You can also use CSS’ @import technique to include one from the other, or use a custom HTML template that adds <link rel="stylesheet"> tags as necessary. Setting the html_style config value will override this setting.

  • The pygments_style setting gives the name of a Pygments style to use for highlighting. This can be overridden by the user in the pygments_style config value.

  • The pygments_dark_style setting gives the name of a Pygments style to use for highlighting when the CSS media query (prefers-color-scheme: dark) evaluates to true. It is injected into the page using add_css_file().

  • The sidebars setting gives the comma separated list of sidebar templates for constructing sidebars. This can be overridden by the user in the html_sidebars config value.

  • The options section contains pairs of variable names and default values. These options can be overridden by the user in html_theme_options and are accessible from all templates as theme_<name>.

Added in version 1.7: sidebar settings

Changed in version 5.1: The stylesheet setting accepts multiple CSS filenames

Convert theme.conf to theme.toml

INI-style theme configuration files (theme.conf) can be converted to TOML via a helper programme distributed with Sphinx. This is intended for one-time use, and may be removed without notice in a future version of Sphinx.

$ python -m sphinx.theming conf_to_toml [THEME DIRECTORY PATH]

The required argument is a path to a directory containing a theme.conf file. The programme will write a theme.toml file in the same directory, and will not modify the original theme.conf file.

Added in version 7.3.

Distribute your theme as a Python package

As a way to distribute your theme, you can use a Python package. This makes it easier for users to set up your theme.

To distribute your theme as a Python package, please define an entry point called sphinx.html_themes in your pyproject.toml file, and write a setup() function to register your theme using the add_html_theme() API:

# pyproject.toml

[project.entry-points."sphinx.html_themes"]
name_of_theme = "your_theme_package"
# your_theme_package.py
from os import path

def setup(app):
    app.add_html_theme('name_of_theme', path.abspath(path.dirname(__file__)))

If your theme package contains two or more themes, please call add_html_theme() twice or more.

Added in version 1.2: ‘sphinx_themes’ entry_points feature.

Deprecated since version 1.6: sphinx_themes entry_points has been deprecated.

Added in version 1.6: sphinx.html_themes entry_points feature.

Templating

The guide to templating is helpful if you want to write your own templates. What is important to keep in mind is the order in which Sphinx searches for templates:

  • First, in the user’s templates_path directories.

  • Then, in the selected theme.

  • Then, in its base theme, its base’s base theme, etc.

When extending a template in the base theme with the same name, use the theme name as an explicit directory: {% extends "basic/layout.html" %}. From a user templates_path template, you can still use the “exclamation mark” syntax as described in the templating document.

Static templates

Since theme options are meant for the user to configure a theme more easily, without having to write a custom stylesheet, it is necessary to be able to template static files as well as HTML files. Therefore, Sphinx supports so-called “static templates”, like this:

If the name of a file in the static/ directory of a theme (or in the user’s static path, for that matter) ends with _t, it will be processed by the template engine. The _t will be left from the final file name. For example, the classic theme has a file static/classic.css_t which uses templating to put the color options into the stylesheet. When a documentation project is built with the classic theme, the output directory will contain a _static/classic.css file where all template tags have been processed.

Use custom page metadata in HTML templates

Any key / value pairs in field lists that are placed before the page’s title will be available to the Jinja template when building the page within the meta attribute. For example, if a page had the following text before its first title:

:mykey: My value

My first title
--------------

Then it could be accessed within a Jinja template like so:

{%- if meta is mapping %}
    {{ meta.get("mykey") }}
{%- endif %}

Note the check that meta is a dictionary (“mapping” in Jinja terminology) to ensure that using it in this way is valid.

Defining custom template functions

Sometimes it is useful to define your own function in Python that you wish to then use in a template. For example, if you’d like to insert a template value with logic that depends on the user’s configuration in the project, or if you’d like to include non-trivial checks and provide friendly error messages for incorrect configuration in the template.

To define your own template function, you’ll need to define two functions inside your module:

  • A page context event handler (or registration) function. This is connected to the Sphinx application via an event callback.

  • A template function that you will use in your Jinja template.

First, define the registration function, which accepts the arguments for html-page-context.

Within the registration function, define the template function that you’d like to use within Jinja. The template function should return a string or Python objects (lists, dictionaries) with strings inside that Jinja uses in the templating process

Note

The template function will have access to all of the variables that are passed to the registration function.

At the end of the registration function, add the template function to the Sphinx application’s context with context['template_func'] = template_func.

Finally, in your extension’s setup() function, add your registration function as a callback for html-page-context.

# The registration function
 def setup_my_func(app, pagename, templatename, context, doctree):
     # The template function
     def my_func(mystring):
         return "Your string is %s" % mystring
     # Add it to the page's context
     context['my_func'] = my_func

 # Your extension's setup function
 def setup(app):
     app.connect("html-page-context", setup_my_func)

Now, you will have access to this function in jinja like so:

<div>
{{ my_func("some string") }}
</div>

Add your own static files to the build assets

By default, Sphinx copies static files on the static/ directory of the template directory. However, if your package needs to place static files outside of the static/ directory for some reasons, you need to copy them to the _static/ directory of HTML outputs manually at the build via an event hook. Here is an example of code to accomplish this:

from os import path
from sphinx.util.fileutil import copy_asset_file

def copy_custom_files(app, exc):
    if app.builder.format == 'html' and not exc:
        staticdir = path.join(app.builder.outdir, '_static')
        copy_asset_file('path/to/myextension/_static/myjsfile.js', staticdir)

def setup(app):
    app.connect('build-finished', copy_custom_files)

Inject JavaScript based on user configuration

If your extension makes use of JavaScript, it can be useful to allow users to control its behavior using their Sphinx configuration. However, this can be difficult to do if your JavaScript comes in the form of a static library (which will not be built with Jinja).

There are two ways to inject variables into the JavaScript space based on user configuration.

First, you may append _t to the end of any static files included with your extension. This will cause Sphinx to process these files with the templating engine, allowing you to embed variables and control behavior.

For example, the following JavaScript structure:

mymodule/
├── _static
│   └── myjsfile.js_t
└── mymodule.py

Will result in the following static file placed in your HTML’s build output:

_build/
└── html
    └── _static
        └── myjsfile.js

See Static templates for more information.

Second, you may use the Sphinx.add_js_file() method without pointing it to a file. Normally, this method is used to insert a new JavaScript file into your site. However, if you do not pass a file path, but instead pass a string to the “body” argument, then this text will be inserted as JavaScript into your site’s head. This allows you to insert variables into your project’s JavaScript from Python.

For example, the following code will read in a user-configured value and then insert this value as a JavaScript variable, which your extension’s JavaScript code may use:

# This function reads in a variable and inserts it into JavaScript
def add_js_variable(app):
    # This is a configuration that you've specified for users in `conf.py`
    js_variable = app.config['my_javascript_variable']
    js_text = "var my_variable = '%s';" % js_variable
    app.add_js_file(None, body=js_text)
# We connect this function to the step after the builder is initialized
def setup(app):
    # Tell Sphinx about this configuration variable
    app.add_config_value('my_javascript_variable', 0, 'html')
    # Run the function after the builder is initialized
    app.connect('builder-inited', add_js_variable)

As a result, in your theme you can use code that depends on the presence of this variable. Users can control the variable’s value by defining it in their conf.py file.