diff --git a/CHANGES b/CHANGES
index a71f25aaa..d970b7ec6 100644
--- a/CHANGES
+++ b/CHANGES
@@ -30,6 +30,9 @@ Features added
 * #9097: Optimize the paralell build
 * #9131: Add :confval:`nitpick_ignore_regex` to ignore nitpicky warnings using
   regular expressions
+* #9174: Add ``Sphinx.add_html_assets_in_all_pages`` to tell extensions to include
+  HTML assets in all the pages. Extensions can check this via
+  ``Sphinx.html_assets_in_all_pages``
 
 
 Bugs fixed
diff --git a/sphinx/application.py b/sphinx/application.py
index 4735beffd..59e1683b3 100644
--- a/sphinx/application.py
+++ b/sphinx/application.py
@@ -146,6 +146,7 @@ class Sphinx:
         self.project: Project = None
         self.registry = SphinxComponentRegistry()
         self.html_themes: Dict[str, str] = {}
+        self.html_assets_in_all_pages: bool = False
 
         # validate provided directories
         self.srcdir = abspath(srcdir)
@@ -1181,6 +1182,13 @@ class Sphinx:
         logger.debug('[app] adding environment collector: %r', collector)
         collector().enable(self)
 
+    def add_html_assets_in_all_pages(self):
+        """Tell extensions to insert HTML assets in all the pages.
+
+        .. versionadded: 4.1
+        """
+        self.html_assets_in_all_pages = True
+
     def add_html_theme(self, name: str, theme_path: str) -> None:
         """Register a HTML Theme.
 
diff --git a/sphinx/ext/mathjax.py b/sphinx/ext/mathjax.py
index 301c0d699..8fc63cb9e 100644
--- a/sphinx/ext/mathjax.py
+++ b/sphinx/ext/mathjax.py
@@ -79,7 +79,7 @@ def install_mathjax(app: Sphinx, pagename: str, templatename: str, context: Dict
                              'mathjax extension to work')
 
     domain = cast(MathDomain, app.env.get_domain('math'))
-    if domain.has_equations(pagename):
+    if app.html_assets_in_all_pages or domain.has_equations(pagename):
         # Enable mathjax only if equations exists
         options = {'async': 'async'}
         if app.config.mathjax_options:
diff --git a/tests/test_ext_math.py b/tests/test_ext_math.py
index ebe2c0f38..52d49ec43 100644
--- a/tests/test_ext_math.py
+++ b/tests/test_ext_math.py
@@ -256,3 +256,16 @@ def test_mathjax_is_not_installed_if_no_equations(app, status, warning):
 
     content = (app.outdir / 'index.html').read_text()
     assert 'MathJax.js' not in content
+
+
+@pytest.mark.sphinx('html', testroot='ext-math',
+                    confoverrides={'extensions': ['sphinx.ext.mathjax']})
+def test_mathjax_is_installed_if_no_equations_when_forced(app, status, warning):
+    app.add_html_assets_in_all_pages()
+    app.builder.build_all()
+
+    content = (app.outdir / 'index.html').read_text()
+    assert MATHJAX_URL in content
+
+    content = (app.outdir / 'nomath.html').read_text()
+    assert MATHJAX_URL in content