diff --git a/core/assets/scaffold/files/default.services.yml b/core/assets/scaffold/files/default.services.yml
index dd6d60e54ea449e90dab795c7ece5a785ed68bc6..45d986cd8e52e2a923dc94eae69fb55bb8fa33ed 100644
--- a/core/assets/scaffold/files/default.services.yml
+++ b/core/assets/scaffold/files/default.services.yml
@@ -118,7 +118,8 @@ parameters:
   # Cacheability debugging:
   #
   # Responses with cacheability metadata (CacheableResponseInterface instances)
-  # get X-Drupal-Cache-Tags and X-Drupal-Cache-Contexts headers.
+  # get X-Drupal-Cache-Tags, X-Drupal-Cache-Contexts and X-Drupal-Cache-Max-Age
+  # headers.
   #
   # For more information about debugging cacheable responses, see
   # https://www.drupal.org/developing/api/8/response/cacheable-response-interface
diff --git a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
index 063369df086e58390677cf08a9eb6960005206e2..c8d76eb294dc7db624ce4effd20054ff39a19e60 100644
--- a/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php
@@ -156,6 +156,14 @@ public function onRespond(ResponseEvent $event) {
       $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())));
+      $max_age_message = $response_cacheability->getCacheMaxAge();
+      if ($max_age_message === 0) {
+        $max_age_message = '0 (Uncacheable)';
+      }
+      elseif ($max_age_message === -1) {
+        $max_age_message = '-1 (Permanent)';
+      }
+      $response->headers->set('X-Drupal-Cache-Max-Age', $max_age_message);
     }
 
     $is_cacheable = ($this->requestPolicy->check($request) === RequestPolicyInterface::ALLOW) && ($this->responsePolicy->check($response, $request) !== ResponsePolicyInterface::DENY);
diff --git a/core/modules/system/tests/src/Functional/Routing/RouterTest.php b/core/modules/system/tests/src/Functional/Routing/RouterTest.php
index 64ac896359bccd4b45742456e16bbc702055f0ae..771d5ac563d619aedaa4029edfdecdae70bf28f3 100644
--- a/core/modules/system/tests/src/Functional/Routing/RouterTest.php
+++ b/core/modules/system/tests/src/Functional/Routing/RouterTest.php
@@ -54,6 +54,7 @@ public function testFinishResponseSubscriber() {
     $headers = $session->getResponseHeaders();
     $this->assertEqual($headers['X-Drupal-Cache-Contexts'], [implode(' ', $expected_cache_contexts)]);
     $this->assertEqual($headers['X-Drupal-Cache-Tags'], ['config:user.role.anonymous http_response rendered']);
+    $this->assertEqual($headers['X-Drupal-Cache-Max-Age'], ['-1 (Permanent)']);
     // Confirm that the page wrapping is being added, so we're not getting a
     // raw body returned.
     $this->assertRaw('</html>', 'Page markup was found.');
@@ -68,6 +69,7 @@ public function testFinishResponseSubscriber() {
     $headers = $session->getResponseHeaders();
     $this->assertEqual($headers['X-Drupal-Cache-Contexts'], [implode(' ', Cache::mergeContexts($renderer_required_cache_contexts, ['url']))]);
     $this->assertEqual($headers['X-Drupal-Cache-Tags'], ['config:user.role.anonymous foo http_response rendered']);
+    $this->assertEqual($headers['X-Drupal-Cache-Max-Age'], ['60']);
     // 2. controller result: render array, per-role cacheable route access.
     $this->drupalGet('router_test/test19');
     $headers = $session->getResponseHeaders();
@@ -78,11 +80,13 @@ public function testFinishResponseSubscriber() {
     $headers = $session->getResponseHeaders();
     $this->assertFalse(isset($headers['X-Drupal-Cache-Contexts']));
     $this->assertFalse(isset($headers['X-Drupal-Cache-Tags']));
+    $this->assertFalse(isset($headers['X-Drupal-Cache-Max-Age']));
     // 4. controller result: Response object, per-role cacheable route access.
     $this->drupalGet('router_test/test20');
     $headers = $session->getResponseHeaders();
     $this->assertFalse(isset($headers['X-Drupal-Cache-Contexts']));
     $this->assertFalse(isset($headers['X-Drupal-Cache-Tags']));
+    $this->assertFalse(isset($headers['X-Drupal-Cache-Max-Age']));
     // 5. controller result: CacheableResponse object, globally cacheable route access.
     $this->drupalGet('router_test/test21');
     $headers = $session->getResponseHeaders();
@@ -100,6 +104,7 @@ public function testFinishResponseSubscriber() {
     $headers = $session->getResponseHeaders();
     $this->assertTrue(isset($headers['X-Drupal-Cache-Contexts']));
     $this->assertTrue(isset($headers['X-Drupal-Cache-Tags']));
+    $this->assertTrue(isset($headers['X-Drupal-Cache-Max-Age']));
     $this->setContainerParameter('http.response.debug_cacheability_headers', FALSE);
     $this->rebuildContainer();
     $this->resetAll();
@@ -107,6 +112,7 @@ public function testFinishResponseSubscriber() {
     $headers = $session->getResponseHeaders();
     $this->assertFalse(isset($headers['X-Drupal-Cache-Contexts']));
     $this->assertFalse(isset($headers['X-Drupal-Cache-Tags']));
+    $this->assertFalse(isset($headers['X-Drupal-Cache-Max-Age']));
   }
 
   /**
diff --git a/sites/default/default.services.yml b/sites/default/default.services.yml
index dd6d60e54ea449e90dab795c7ece5a785ed68bc6..45d986cd8e52e2a923dc94eae69fb55bb8fa33ed 100644
--- a/sites/default/default.services.yml
+++ b/sites/default/default.services.yml
@@ -118,7 +118,8 @@ parameters:
   # Cacheability debugging:
   #
   # Responses with cacheability metadata (CacheableResponseInterface instances)
-  # get X-Drupal-Cache-Tags and X-Drupal-Cache-Contexts headers.
+  # get X-Drupal-Cache-Tags, X-Drupal-Cache-Contexts and X-Drupal-Cache-Max-Age
+  # headers.
   #
   # For more information about debugging cacheable responses, see
   # https://www.drupal.org/developing/api/8/response/cacheable-response-interface