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# `sphinx.ext.extlinks` – Markup to shorten external links

Module author: Georg Brandl

New in version 1.0.

This extension is meant to help with the common pattern of having many external links that point to URLs on one and the same site, e.g. links to bug trackers, version control web interfaces, or simply subpages in other websites. It does so by providing aliases to base URLs, so that you only need to give the subpage name when creating a link.

Let’s assume that you want to include many links to issues at the Sphinx tracker, at `https://github.com/sphinx-doc/sphinx/issues/num`. Typing this URL again and again is tedious, so you can use `extlinks` to avoid repeating yourself.

The extension adds one new config value:

`extlinks`

  This config value must be a dictionary of external sites, mapping unique short alias names to a base URL and a prefix. For example, to create an alias for the above mentioned issues, you would add

      extlinks = {'issue': ('https://github.com/sphinx-doc/sphinx/issues/%s',
                            'issue ')}

  Now, you can use the alias name as a new role, e.g. `:issue:`123``. This then inserts a link to https://github.com/sphinx-doc/sphinx/issues/123. As you can see, the target given in the role is substituted in the base URL in the place of `%s`.

  The link caption depends on the second item in the tuple, the prefix:

  - If the prefix is `None`, the link caption is the full URL.
  - If the prefix is the empty string, the link caption is the partial URL given in the role content (`123` in this case.)
  - If the prefix is a non-empty string, the link caption is the partial URL, prepended by the prefix – in the above example, the link caption would be `issue 123`.

  You can also use the usual “explicit title” syntax supported by other roles that generate links, i.e. `:issue:`this issue <123>``. In this case, the prefix is not relevant.

Note

Since links are generated from the role in the reading stage, they appear as ordinary links to e.g. the `linkcheck` builder.