.. _xref:

================ Cross-references

One of Sphinx's most useful features is creating automatic cross-references through semantic cross-referencing roles. A cross reference to an object description, such as :func:`spam```, will create a link to the place where spam()`` is documented, appropriate to each output format (HTML, PDF, ePUB, etc.).

.. _xref-syntax:

Syntax

Sphinx supports various cross-referencing roles to create links to other elements in the documentation. In general, writing ``:role:`target``` creates a link to the object called target of the type indicated by role. The link's text depends the role but is often the same as or similar to target.

.. _xref-modifiers:

The behavior can be modified in the following ways:

Custom link text: You can specify the link text explicitly using the same notation as in reStructuredText :ref:external links <rst-external-links>: ``:role:`custom text <target>``` will refer to target and display custom text as the text of the link.
Suppressed link: Prefixing with an exclamation mark (!) prevents the creation of a link but otherwise keeps the visual output of the role.

For example, writing ``:py:func:!target``` displays :py:func:!target`, with no link generated.

This is helpful for cases in which the link target does not exist; e.g. changelog entries that describe removed functionality, or third-party libraries that don't support :doc:intersphinx </usage/extensions/intersphinx>. Suppressing the link prevents warnings in :confval:nitpicky mode.
Modified domain reference: When :ref:referencing domain objects <ref-objects>, a tilde ~ prefix shortens the link text to the last component of the target. For example, :py:meth:`~queue.Queue.get``` will refer to queue.Queue.getbut only displayget`` as the link text.

In HTML output, the link's title attribute (that is e.g. shown as a tool-tip on mouse-hover) will always be the full target name.

.. _ref-objects:

Cross-referencing objects

These roles are described with their respective domains:

:ref:C <c-xref-roles>
:ref:C++ <cpp-xref-roles>
:ref:JavaScript <js-xref-roles>
:ref:reStructuredText <rst-xref-roles>
:ref:Python <python-xref-roles>

.. _ref-role:

Cross-referencing arbitrary locations

.. rst:role:: ref

To support cross-referencing to arbitrary locations in any document, the standard reStructuredText labels are used. For this to work label names must be unique throughout the entire documentation. There are two ways in which you can refer to labels:

If you place a label directly before a section title, you can reference to it with ``:ref:`label-name```. For example::

.. _my-reference-label:

Section to cross-reference

This is the text of the section.

It refers to the section itself, see :ref:my-reference-label.

The :ref: role would then generate a link to the section, with the link title being "Section to cross-reference". This works just as well when section and reference are in different source files.

Automatic labels also work with figures. For example::

.. _my-figure:

.. figure:: whatever
```
  Figure caption
```
In this case, a reference ``:ref:`my-figure``` would insert a reference to the figure with link text "Figure caption".

The same works for tables that are given an explicit caption using the :dudir:table directive.
Labels that aren't placed before a section title can still be referenced, but you must give the link an explicit title, using this syntax: ``:ref:`Link title <label-name>```.

.. note::

  Reference labels must start with an underscore. When referencing a label,
  the underscore must be omitted (see examples above).

Using :rst:role:ref is advised over standard reStructuredText links to sections (like ```Section title`_``) because it works across files, when section headings are changed, will raise warnings if incorrect, and works for all builders that support cross-references.

Cross-referencing documents

.. versionadded:: 0.6

There is also a way to directly link to documents:

.. rst:role:: doc

Link to the specified document; the document name can be a relative or absolute path and is always case-sensitive, even on Windows. For example, if the reference :doc:`parrot``` occurs in the document sketches/index, then the link refers to sketches/parrot. If the reference is :doc:/people``` or ``:doc:../people```, the link refers to people.

If no explicit link text is given (like usual: ``:doc:`Monty Python members </people>```), the link caption will be the title of the given document.

Referencing downloadable files

.. versionadded:: 0.6

.. rst:role:: download

This role lets you link to files within your source tree that are not reStructuredText documents that can be viewed, but files that can be downloaded.

When you use this role, the referenced file is automatically marked for inclusion in the output when building (obviously, for HTML output only). All downloadable files are put into a _downloads/<unique hash>/ subdirectory of the output directory; duplicate filenames are handled.

An example::

  See :download:`this example script <../example.py>`.

The given filename is usually relative to the directory the current source file is contained in, but if it absolute (starting with /), it is taken as relative to the top source directory.

The example.py file will be copied to the output directory, and a suitable link generated to it.

Not to show unavailable download links, you should wrap whole paragraphs that have this role::

  .. only:: builder_html

     See :download:`this example script <../example.py>`.

Cross-referencing figures by figure number

.. versionadded:: 1.3

.. versionchanged:: 1.5 :rst:role:numref role can also refer sections. And :rst:role:numref allows {name} for the link text.

.. rst:role:: numref

Link to the specified figures, tables, code-blocks and sections; the standard reStructuredText labels are used. When you use this role, it will insert a reference to the figure with link text by its figure number like "Fig. 1.1".

If an explicit link text is given (as usual: ``:numref:Image of Sphinx (Fig. %s) <my-figure>```), the link caption will serve as title of the reference. As placeholders, %sand{number}get replaced by the figure number and {name} by the figure caption. If no explicit link text is given, the :confval:numfig_format` setting is used as fall-back default.

If :confval:numfig is False, figures are not numbered, so this role inserts not a reference but the label or the link text.

Cross-referencing other items of interest

The following roles do possibly create a cross-reference, but do not refer to objects:

.. rst:role:: confval

A configuration value or setting. Index entries are generated. Also generates a link to the matching :rst:dir:confval directive, if it exists.

.. rst:role:: envvar

An environment variable. Index entries are generated. Also generates a link to the matching :rst:dir:envvar directive, if it exists.

.. rst:role:: token

The name of a grammar token (used to create links between :rst:dir:productionlist directives).

.. rst:role:: keyword

The name of a keyword in Python. This creates a link to a reference label with that name, if it exists.

.. rst:role:: option

A command-line option to an executable program. This generates a link to a :rst:dir:option directive, if it exists.

The following role creates a cross-reference to a term in a :ref:glossary <glossary-directive>:

.. rst:role:: term

Reference to a term in a glossary. A glossary is created using the glossary directive containing a definition list with terms and definitions. It does not have to be in the same file as the term markup, for example the Python docs have one global glossary in the glossary.rst file.

If you use a term that's not explained in a glossary, you'll get a warning during build.

This role also supports :ref:custom link text <xref-modifiers> from the general cross-reference syntax.

.. _any-role:

Cross-referencing anything

.. rst:role:: any

.. versionadded:: 1.3

This convenience role tries to do its best to find a valid target for its reference text.

First, it tries standard cross-reference targets that would be referenced by :rst:role:doc, :rst:role:ref or :rst:role:option.

Custom objects added to the standard domain by extensions (see :meth:.Sphinx.add_object_type) are also searched.
Then, it looks for objects (targets) in all loaded domains. It is up to the domains how specific a match must be. For example, in the Python domain a reference of :any:`Builder``` would match the sphinx.builders.Builder`` class.

If none or multiple targets are found, a warning will be emitted. In the case of multiple targets, you can change "any" to a specific role.

This role is a good candidate for setting :confval:default_role. If you do, you can write cross-references without a lot of markup overhead. For example, in this Python function documentation::

  .. function:: install()

     This function installs a `handler` for every signal known by the
     `signal` module.  See the section `about-signals` for more information.

there could be references to a glossary term (usually :term:`handler```), a Python module (usually :py:mod:signal``` or ``:mod:signal) and a section (usually ``:ref:`about-signals).

The :rst:role:any role also works together with the :mod:~sphinx.ext.intersphinx extension: when no local cross-reference is found, all object types of intersphinx inventories are also searched.

Cross-references