core/core.services.yml                               |  4 ++--
 ...onSubscriber.php => FinalExceptionSubscriber.php} | 20 +++++++++++++++++---
 ...iberTest.php => FinalExceptionSubscriberTest.php} |  8 ++++----
 3 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/core/core.services.yml b/core/core.services.yml
index 40c6a8a..0c91b8c 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1230,8 +1230,8 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@http_kernel', '@logger.channel.php', '@redirect.destination', '@router.no_access_checks']
-  exception.default:
-    class: Drupal\Core\EventSubscriber\DefaultExceptionSubscriber
+  exception.final:
+    class: Drupal\Core\EventSubscriber\FinalExceptionSubscriber
     tags:
       - { name: event_subscriber }
     arguments: ['@config.factory']
diff --git a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/FinalExceptionSubscriber.php
similarity index 86%
rename from core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
rename to core/lib/Drupal/Core/EventSubscriber/FinalExceptionSubscriber.php
index 4d3bffc..2d6f022 100644
--- a/core/lib/Drupal/Core/EventSubscriber/DefaultExceptionSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/FinalExceptionSubscriber.php
@@ -13,12 +13,25 @@
 use Symfony\Component\HttpKernel\KernelEvents;
 
 /**
- * Last-chance handler for exceptions.
+ * Last-chance handler for exceptions: the final exception subscriber.
  *
  * This handler will catch any exceptions not caught elsewhere and report
  * them as an error page.
+ *
+ * Each format has its own way of handling exceptions:
+ * - html: exception.default_html, exception.custom_page_html and
+ *   exception.fast_404_html
+ * - json: exception.default_json
+ *
+ * And when the serialization module is installed, all serialization formats are
+ * handled by a single exception subscriber:: serialization.exception.default.
+ *
+ * This exception subscriber runs after all the above (it has a lower priority),
+ * which makes it the last-chance exception handler. It always sends a plain
+ * text response. If it's a displayable error and the error level is configured
+ * to be verbose, then a helpful backtrace is also printed.
  */
-class DefaultExceptionSubscriber implements EventSubscriberInterface {
+class FinalExceptionSubscriber implements EventSubscriberInterface {
   use StringTranslationTrait;
 
   /**
@@ -36,7 +49,7 @@ class DefaultExceptionSubscriber implements EventSubscriberInterface {
   protected $configFactory;
 
   /**
-   * Constructs a new DefaultExceptionSubscriber.
+   * Constructs a new FinalExceptionSubscriber.
    *
    * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
    *   The configuration factory.
@@ -129,6 +142,7 @@ public function onException(GetResponseForExceptionEvent $event) {
    * {@inheritdoc}
    */
   public static function getSubscribedEvents() {
+    // Run as the final (very late) KernelEvents::EXCEPTION subscriber.
     $events[KernelEvents::EXCEPTION][] = ['onException', -256];
     return $events;
   }
diff --git a/core/tests/Drupal/Tests/Core/EventSubscriber/DefaultExceptionSubscriberTest.php b/core/tests/Drupal/Tests/Core/EventSubscriber/FinalExceptionSubscriberTest.php
similarity index 87%
rename from core/tests/Drupal/Tests/Core/EventSubscriber/DefaultExceptionSubscriberTest.php
rename to core/tests/Drupal/Tests/Core/EventSubscriber/FinalExceptionSubscriberTest.php
index a0a48a1..aaf6982 100644
--- a/core/tests/Drupal/Tests/Core/EventSubscriber/DefaultExceptionSubscriberTest.php
+++ b/core/tests/Drupal/Tests/Core/EventSubscriber/FinalExceptionSubscriberTest.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Tests\Core\EventSubscriber;
 
-use Drupal\Core\EventSubscriber\DefaultExceptionSubscriber;
+use Drupal\Core\EventSubscriber\FinalExceptionSubscriber;
 use Drupal\Tests\UnitTestCase;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -11,10 +11,10 @@
 use Symfony\Component\HttpKernel\HttpKernelInterface;
 
 /**
- * @coversDefaultClass \Drupal\Core\EventSubscriber\DefaultExceptionSubscriber
+ * @coversDefaultClass \Drupal\Core\EventSubscriber\FinalExceptionSubscriber
  * @group EventSubscriber
  */
-class DefaultExceptionSubscriberTest extends UnitTestCase {
+class FinalExceptionSubscriberTest extends UnitTestCase {
 
   /**
    * @covers ::onException
@@ -41,7 +41,7 @@ public function testOnExceptionWithUnknownFormat() {
 
 }
 
-class TestDefaultExceptionSubscriber extends DefaultExceptionSubscriber {
+class TestDefaultExceptionSubscriber extends FinalExceptionSubscriber {
 
   protected function isErrorDisplayable($error) {
     return TRUE;