diff --git a/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php b/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php
index c6b49ab..8ef248e 100644
--- a/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php
+++ b/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php
@@ -55,7 +55,16 @@ public function handle(Request $request, $type = self::MASTER_REQUEST, $catch =
         $request::setTrustedProxies($proxies);
       }
     }
-    return $this->httpKernel->handle($request, $type, $catch);
+
+    $response = $this->httpKernel->handle($request, $type, $catch);
+
+    // X-Drupal-Cache-Contexts and X-Drupal-Cache-Tags header respectively, when
+    // either a reverse proxy is being used (so the reverse proxy or CDN can be
+    // invalidated when appropriate) or when developing/debugging.
+    if (!($this->settings->get('reverse_proxy', FALSE) || $this->settings->get('send_cacheability_headers', FALSE))) {
+      $response->headers->remove('X-Drupal-Cache-Tags');
+      $response->headers->remove('X-Drupal-Cache-Contexts');
+    }
   }
 
 }
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 4418bd4..8c88f40 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -761,7 +761,7 @@ protected function prepareSettings() {
       'value' => FALSE,
       'required' => TRUE,
     ];
-    
+
     $this->writeSettings($settings);
     // Allow for test-specific overrides.
     $settings_testing_file = DRUPAL_ROOT . '/' . $this->originalSite . '/settings.testing.php';
diff --git a/sites/example.settings.local.php b/sites/example.settings.local.php
index a5d50f2..dacc687 100644
--- a/sites/example.settings.local.php
+++ b/sites/example.settings.local.php
@@ -73,6 +73,13 @@
 # $settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.null';
 
 /**
+ * Send cacheablity headers for debugging purposes.
+ *
+ * By default, cacheability headers are only sent when behind a reverse proxy.
+ */
+# $settings['send_cacheability_headers'] = TRUE;
+
+/**
  * Allow test modules and themes to be installed.
  *
  * Drupal ignores test modules and themes by default for performance reasons.