Fixed #35505 -- Added extrabody block to admin/base.html.

django/contrib/admin/templates/admin/base.html

@@ -121,5 +121,6 @@
   <symbol viewBox="0 0 24 24" width="1rem" height="1rem" id="icon-sun"><path d="M0 0h24v24H0z" fill="currentColor"/><path d="M12 18a6 6 0 1 1 0-12 6 6 0 0 1 0 12zm0-2a4 4 0 1 0 0-8 4 4 0 0 0 0 8zM11 1h2v3h-2V1zm0 19h2v3h-2v-3zM3.515 4.929l1.414-1.414L7.05 5.636 5.636 7.05 3.515 4.93zM16.95 18.364l1.414-1.414 2.121 2.121-1.414 1.414-2.121-2.121zm2.121-14.85l1.414 1.415-2.121 2.121-1.414-1.414 2.121-2.121zM5.636 16.95l1.414 1.414-2.121 2.121-1.414-1.414 2.121-2.121zM23 11v2h-3v-2h3zM4 11v2H1v-2h3z"/></symbol>
 </svg>
 <!-- END SVGs -->
+{% block extrabody %}{% endblock extrabody %}
 </body>
 </html>

docs/ref/contrib/admin/index.txt

@@ -2827,6 +2827,32 @@ linked to the document in ``{% block dark-mode-vars %}``.
 
 .. _prefers-color-scheme: https://developer.mozilla.org/en-US/docs/Web/CSS/@media/prefers-color-scheme
 
+.. _extrabody:
+
+``extrabody`` block
+===================
+
+.. versionadded:: 5.2
+
+You can add custom HTML, JavaScript, or other content to appear just before the
+closing ``</body>`` tag of templates that extend ``admin/base.html`` by
+extending the ``extrabody`` block. For example, if you want an alert to appear
+on page load you could add a ``admin/base.html`` template override to your
+project:
+
+.. code-block:: html+django
+
+    {% extends 'admin/base.html' %}
+
+    {% block extrabody %}
+        {{ block.super }}
+        <script>
+            document.addEventListener('DOMContentLoaded', function() {
+                window.alert('Welcome!');
+            });
+        </script>
+    {% endblock extrabody %}
+
 ``AdminSite`` objects
 =====================
 

docs/releases/5.2.txt

@@ -37,7 +37,9 @@ Minor features
 :mod:`django.contrib.admin`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-* ...
+* The ``admin/base.html`` template now has a new block
+  :ref:`extrabody <extrabody>` for adding custom code before the closing
+  ``</body>`` tag.
 
 :mod:`django.contrib.admindocs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

tests/admin_views/templates/admin/base_site.html

@@ -1,3 +1,5 @@
 {% extends "admin/base.html" %}
 
 {% block bodyclass %}bodyclass_consistency_check{% endblock %}
+
+{% block extrabody %}extrabody_check{% endblock extrabody %}

tests/admin_views/tests.py

@@ -1746,6 +1746,10 @@ def test_extended_bodyclass_template_change_form(self):
         response = self.client.get(reverse("admin:admin_views_section_add"))
         self.assertContains(response, "bodyclass_consistency_check ")
 
+    def test_extended_extrabody(self):
+        response = self.client.get(reverse("admin:admin_views_section_add"))
+        self.assertContains(response, "extrabody_check\n</body>")
+
     def test_change_password_template(self):
         user = User.objects.get(username="super")
         response = self.client.get(