=========================
How to override templates
=========================

In your project, you might want to override a template in another Django
application, whether it be a third-party application or a contrib application
such as ``django.contrib.admin``. You can either put template overrides in your
project's templates directory or in an application's templates directory.

If you have app and project templates directories that both contain overrides,
the default Django template loader will try to load the template from the
project-level directory first. In other words, :setting:`DIRS <TEMPLATES-DIRS>`
is searched before :setting:`APP_DIRS <TEMPLATES-APP_DIRS>`.

.. seealso::

   Read :ref:`overriding-built-in-widget-templates` if you're looking to
   do that.

Overriding from the project's templates directory
=================================================

First, we'll explore overriding templates by creating replacement templates in
your project's templates directory.

Let's say you're trying to override the templates for a third-party application
called ``blog``, which provides the templates ``blog/post.html`` and
``blog/list.html``. The relevant settings for your project would look like::

    from pathlib import Path

    BASE_DIR = Path(__file__).resolve().parent.parent

    INSTALLED_APPS = [
        ...,
        'blog',
        ...,
    ]

    TEMPLATES = [
        {
            'BACKEND': 'django.template.backends.django.DjangoTemplates',
            'DIRS': [BASE_DIR / 'templates'],
            'APP_DIRS': True,
            ...
        },
    ]

The :setting:`TEMPLATES` setting and ``BASE_DIR`` will already exist if you
created your project using the default project template. The setting that needs
to be modified is :setting:`DIRS<TEMPLATES-DIRS>`.

These settings assume you have a ``templates`` directory in the root of your
project. To override the templates for the ``blog`` app, create a folder
in the ``templates`` directory, and add the template files to that folder:

.. code-block:: none

    templates/
        blog/
            list.html
            post.html

The template loader first looks for templates in the ``DIRS`` directory. When
the views in the ``blog`` app ask for the ``blog/post.html`` and
``blog/list.html`` templates, the loader will return the files you just created.

Overriding from an app's template directory
===========================================

Since you're overriding templates located outside of one of your project's
apps, it's more common to use the first method and put template overrides in a
project's templates folder. If you prefer, however, it's also possible to put
the overrides in an app's template directory.

First, make sure your template settings are checking inside app directories::

    TEMPLATES = [
        {
            ...,
            'APP_DIRS': True,
            ...
        },
    ]

If you want to put the template overrides in an app called ``myapp`` and the
templates to override are named ``blog/list.html`` and ``blog/post.html``,
then your directory structure will look like:

.. code-block:: none

    myapp/
        templates/
            blog/
                list.html
                post.html

With :setting:`APP_DIRS<TEMPLATES-APP_DIRS>` set to ``True``, the template
loader will look in the app's templates directory and find the templates.

.. _extending_an_overridden_template:

Extending an overridden template
================================

With your template loaders configured, you can extend a template using the
:ttag:`{% extends %}<extends>` template tag whilst at the same time overriding
it. This can allow you to make small customizations without needing to
reimplement the entire template.

For example, you can use this technique to add a custom logo to the
``admin/base_site.html`` template:

    .. code-block:: html+django
       :caption: ``templates/admin/base_site.html``

        {% extends "admin/base_site.html" %}

        {% block branding %}
            <img src="link/to/logo.png" alt="logo">
            {{ block.super }}
        {% endblock %}

Key points to note:

* The example creates a file at ``templates/admin/base_site.html`` that uses
  the configured project-level ``templates`` directory to override
  ``admin/base_site.html``.
* The new template extends ``admin/base_site.html``, which is the same template
  as is being overridden.
* The template replaces just the ``branding`` block, adding a custom logo, and
  using ``block.super`` to retain the prior content.
* The rest of the template is inherited unchanged from
  ``admin/base_site.html``.

This technique works because the template loader does not consider the already
loaded override template (at ``templates/admin/base_site.html``) when
resolving the ``extends`` tag. Combined with ``block.super`` it is a powerful
technique to make small customizations.
