diff --git a/core/core.services.yml b/core/core.services.yml
index f91e5976f3..4c4e49bc0b 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1150,6 +1150,10 @@ services:
     tags:
       - { name: event_subscriber }
     arguments: ['@resolver_manager.entity']
+  ajax.ajax_page_state_listener:
+    class: Drupal\Core\Ajax\AjaxPageStateSubscriber
+    tags:
+      - { name: 'event_subscriber' }
   ajax_response.subscriber:
     class: Drupal\Core\EventSubscriber\AjaxResponseSubscriber
     arguments: ['@ajax_response.attachments_processor']
diff --git a/core/lib/Drupal/Core/Ajax/AjaxPageStateSubscriber.php b/core/lib/Drupal/Core/Ajax/AjaxPageStateSubscriber.php
new file mode 100644
index 0000000000..4d24246980
--- /dev/null
+++ b/core/lib/Drupal/Core/Ajax/AjaxPageStateSubscriber.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace Drupal\Core\Ajax;
+
+use Drupal\Component\Utility\UrlHelper;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpKernel\Event\KernelEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * Replaces a compressed ajax_page_state query parameter with an array.
+ */
+class AjaxPageStateSubscriber implements EventSubscriberInterface {
+
+  /**
+   * Replaces a compressed ajax_page_state request parameter with an array.
+   *
+   * @param \Symfony\Component\HttpKernel\Event\KernelEvent $event
+   *   The event to process.
+   */
+  public function onRequest(KernelEvent $event) {
+    $request = $event->getRequest();
+    if ($request->request->has('ajax_page_state')) {
+      $ajax_page_state = $request->request->get('ajax_page_state');
+      $ajax_page_state = json_decode(UrlHelper::uncompressQueryParameter($ajax_page_state), TRUE);
+      $request->request->set('ajax_page_state', $ajax_page_state);
+    }
+    if ($request->query->has('ajax_page_state')) {
+      $ajax_page_state = $request->query->get('ajax_page_state');
+      $ajax_page_state = json_decode(UrlHelper::uncompressQueryParameter($ajax_page_state), TRUE);
+      $request->query->set('ajax_page_state', $ajax_page_state);
+      $request->request->set('ajax_page_state', $ajax_page_state);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents(): array {
+    $events[KernelEvents::REQUEST][] = ['onRequest'];
+    return $events;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/Asset/AssetResolver.php b/core/lib/Drupal/Core/Asset/AssetResolver.php
index 42b51c39d8..0eaf6e8dee 100644
--- a/core/lib/Drupal/Core/Asset/AssetResolver.php
+++ b/core/lib/Drupal/Core/Asset/AssetResolver.php
@@ -4,6 +4,7 @@
 
 use Drupal\Component\Utility\Crypt;
 use Drupal\Component\Utility\NestedArray;
+use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Language\LanguageManagerInterface;
@@ -325,6 +326,11 @@ public function getJsAssets(AttachedAssetsInterface $assets, $optimize, Language
       // Update the $assets object accordingly, so that it reflects the final
       // settings.
       $assets->setSettings($settings);
+      // Convert ajaxPageState to a compressed string from an array, since it is
+      // used by ajax.js to pass to AJAX requests as a query parameter.
+      if (isset($settings['ajaxPageState'])) {
+        $settings['ajaxPageState'] = UrlHelper::compressQueryParameter(json_encode($settings['ajaxPageState']));
+      }
       $settings_as_inline_javascript = [
         'type' => 'setting',
         'group' => JS_SETTING,
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index 32d8cf08ac..b56b471923 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -824,13 +824,11 @@
 
     // Allow Drupal to return new JavaScript and CSS files to load without
     // returning the ones already loaded.
+    // @see \Drupal\Core\Ajax\AjaxPageStateSubscriber
     // @see \Drupal\Core\Theme\AjaxBasePageNegotiator
     // @see \Drupal\Core\Asset\LibraryDependencyResolverInterface::getMinimalRepresentativeSubset()
     // @see system_js_settings_alter()
-    const pageState = drupalSettings.ajaxPageState;
-    options.data['ajax_page_state[theme]'] = pageState.theme;
-    options.data['ajax_page_state[theme_token]'] = pageState.theme_token;
-    options.data['ajax_page_state[libraries]'] = pageState.libraries;
+    options.data.ajax_page_state = drupalSettings.ajaxPageState;
   };
 
   /**
diff --git a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
index 246cd47a64..09c612a7a4 100644
--- a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
+++ b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
@@ -184,7 +184,7 @@ public function testBigPipe() {
 
     // Verifying BigPipe assets are present.
     $this->assertNotEmpty($this->getDrupalSettings());
-    $this->assertContains('big_pipe/big_pipe', explode(',', $this->getDrupalSettings()['ajaxPageState']['libraries']), 'BigPipe asset library is present.');
+    $this->assertContains('big_pipe/big_pipe', explode(',', $this->getDrupalSettingsUncompressed()['ajaxPageState']['libraries']), 'BigPipe asset library is present.');
 
     // Verify that the two expected exceptions are logged as errors.
     $this->assertEquals($log_count + 2, (int) $connection->select('watchdog')->countQuery()->execute()->fetchField(), 'Two new watchdog entries.');
diff --git a/core/modules/comment/tests/src/Functional/CommentCSSTest.php b/core/modules/comment/tests/src/Functional/CommentCSSTest.php
index 5ad9c93248..1b3169e2d1 100644
--- a/core/modules/comment/tests/src/Functional/CommentCSSTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentCSSTest.php
@@ -89,7 +89,7 @@ public function testCommentClasses() {
       }
       // Request the node with the comment.
       $this->drupalGet('node/' . $node->id());
-      $settings = $this->getDrupalSettings();
+      $settings = $this->getDrupalSettingsUncompressed();
 
       // Verify the data-history-node-id attribute, which is necessary for the
       // by-viewer class and the "new" indicator, see below.
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index 4bb41d8f71..8f1404cb55 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -8,6 +8,7 @@
 use Behat\Mink\Selector\SelectorsHandler;
 use Behat\Mink\Session;
 use Drupal\Component\Serialization\Json;
+use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Database\Database;
 use Drupal\Core\Test\FunctionalTestSetupTrait;
 use Drupal\Core\Test\TestSetupTrait;
@@ -624,6 +625,21 @@ protected function getDrupalSettings() {
     return [];
   }
 
+  /**
+   * Gets the value of drupalSettings with ajaxPageState uncompressed.
+   *
+   * @return array
+   *   The Drupal settings array, with the ajaxPageState key uncompressed.
+   */
+  protected function getDrupalSettingsUncompressed() {
+    $settings = $this->getDrupalSettings();
+    if (isset($settings['ajaxPageState'])) {
+      $settings['ajaxPageState'] = json_decode(UrlHelper::uncompressQueryParameter($settings['ajaxPageState']), 1);
+    }
+    return $settings;
+  }
+
+
   /**
    * Retrieves the current calling line in the class under test.
    *