diff --git a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
index c22107f..3f22250 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
@@ -117,7 +117,9 @@ public function onRespond(FilterResponseEvent $event) {
 
     // Expose the cache contexts and cache tags associated with this page in a
     // X-Drupal-Cache-Contexts and X-Drupal-Cache-Tags header respectively.
-    if (Settings::get('reverse_proxy', FALSE) && $response instanceof CacheableResponseInterface) {
+    // We just want to send the cacheability headers in case it is actually
+    // needed, so a reverse proxy is used, or when we want to debug its values.
+    if ((Settings::get('reverse_proxy', FALSE) || Settings::get('send_cacheability_headers', FALSE)) && $response instanceof CacheableResponseInterface) {
       $response_cacheability = $response->getCacheableMetadata();
       $response->headers->set('X-Drupal-Cache-Tags', implode(' ', $response_cacheability->getCacheTags()));
       $response->headers->set('X-Drupal-Cache-Contexts', implode(' ', $this->cacheContextsManager->optimizeTokens($response_cacheability->getCacheContexts())));
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 2ac0d4b..c053110 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -742,6 +742,14 @@ protected function prepareSettings() {
       'value' => FALSE,
       'required' => TRUE,
     ];
+
+    // Enable to send cacheability metadata headers for tests in order to check
+    // their values.
+    $settings['settings']['send_cacheability_headers'] = (object) [
+      'value' => TRUE,
+      '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 34b4e19..8abdb00 100644
--- a/sites/example.settings.local.php
+++ b/sites/example.settings.local.php
@@ -76,3 +76,8 @@
  * using these parameters in a request to rebuild.php.
  */
 $settings['rebuild_access'] = TRUE;
+
+/**
+ * Send cacheablity metadata for debugging purposes.
+ */
+$settings['send_cacheability_headers'] = TRUE;