diff --git a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/AccessibilityChecker.php b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/AccessibilityChecker.php
new file mode 100644
index 0000000..7fd358f
--- /dev/null
+++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/AccessibilityChecker.php
@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\ckeditor\Plugin\CKEditorPlugin;
+
+use Drupal\ckeditor\CKEditorPluginBase;
+use Drupal\ckeditor\CKEditorPluginCssInterface;
+use Drupal\editor\Entity\Editor;
+
+/**
+ * Defines the "A11ychecker" plugin.
+ *
+ * @CKEditorPlugin(
+ *   id = "AccessibilityChecker",
+ *   label = @Translation("Accessibility Checker")
+ * )
+ */
+class AccessibilityChecker extends CKEditorPluginBase implements CKEditorPluginCssInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isInternal() {
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFile() {
+    // This plugin is already part of Drupal core's CKEditor build.
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getLibraries(Editor $editor) {
+    return [];
+  }
+
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConfig(Editor $editor) {
+    return [];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getButtons() {
+    return [
+      'A11ychecker' => [
+        'label' => $this->t('Accessibility Checker'),
+        'image_alternative' => [
+          '#type' => 'inline_template',
+          '#template' => '<a href="#" class="cke-icon-only" role="button" title="' . $this->t('Accessibility Checker') . '" aria-label="' . $this->t('Accessibility Checker') . '"><span class="cke_button_icon cke_button__a11ychecker_icon">' . $this->t('Accessibility Checker') . '</span></a>',
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  function getCssFiles(Editor $editor) {
+    return [];
+  }
+
+}