diff --git a/core/lib/Drupal/Component/Utility/Json.php b/core/lib/Drupal/Component/Utility/Json.php
index 54614b5..0715e13 100644
--- a/core/lib/Drupal/Component/Utility/Json.php
+++ b/core/lib/Drupal/Component/Utility/Json.php
@@ -39,9 +39,6 @@ public static function encode($variable) {
    *
    * @return mixed
    *   Returns the decoded string.
-   *
-   * @see drupal_json_encode()
-   * @ingroup php_wrappers
    */
   public static function decode($string) {
     return json_decode($string, TRUE);
diff --git a/core/lib/Drupal/Core/Asset/JsCollectionRenderer.php b/core/lib/Drupal/Core/Asset/JsCollectionRenderer.php
index 1173012..cdaf1d8 100644
--- a/core/lib/Drupal/Core/Asset/JsCollectionRenderer.php
+++ b/core/lib/Drupal/Core/Asset/JsCollectionRenderer.php
@@ -7,6 +7,7 @@
 namespace Drupal\Core\Asset;
 
 use Drupal\Core\KeyValueStore\StateInterface;
+use Drupal\Component\Utility\Json;
 
 /**
  * Renders JavaScript assets.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
index 11e7e22..03f37e1 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/Editor/CKEditor.php
@@ -16,7 +16,6 @@
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\editor\Entity\Editor as EditorEntity;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Drupal\Component\Utility\Json;
 
 /**
  * Defines a CKEditor-based text editor for Drupal.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
index 7663d27..f984160 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
@@ -9,7 +9,6 @@
 
 use Drupal\editor\Entity\Editor;
 use Drupal\simpletest\WebTestBase;
-use Drupal\Component\Utility\Json;
 
 /**
  * Tests administration of CKEditor.
@@ -154,7 +153,7 @@ function testAdmin() {
       array('JustifyCenter')
     );
     $edit = array(
-      'editor[settings][toolbar][buttons]' => Json::encode($expected_settings['toolbar']['buttons']),
+      'editor[settings][toolbar][button_groups]' => json_encode($expected_settings['toolbar']['rows']),
     );
     $this->drupalPostForm(NULL, $edit, t('Save configuration'));
     $editor = entity_load('editor', 'filtered_html');
diff --git a/core/modules/config/lib/Drupal/config/Form/ConfigSync.php b/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
index 45c6973..8e95d7e 100644
--- a/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
+++ b/core/modules/config/lib/Drupal/config/Form/ConfigSync.php
@@ -20,7 +20,6 @@
 use Drupal\Core\Routing\UrlGeneratorInterface;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
-use Drupal\Component\Utility\Json;
 
 /**
  * Construct the storage changes in a configuration synchronization form.
@@ -210,7 +209,7 @@ public function buildForm(array $form, array &$form_state) {
           'attributes' => array(
             'class' => array('use-ajax'),
             'data-accepts' => 'application/vnd.drupal-modal',
-            'data-dialog-options' => Json::encode(array(
+            'data-dialog-options' => json_encode(array(
               'width' => 700
             )),
           ),
diff --git a/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php b/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
index 20499a3..5903780 100644
--- a/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
+++ b/core/modules/rest/lib/Drupal/rest/Tests/Views/StyleSerializerTest.php
@@ -9,7 +9,6 @@
 
 use Drupal\views\Tests\Plugin\PluginTestBase;
 use Drupal\views\Tests\ViewTestData;
-use Drupal\Component\Utility\Json;
 
 /**
  * Tests the serializer style plugin.
@@ -88,7 +87,7 @@ public function testSerializerResponses() {
       $expected[] = $expected_row;
     }
 
-    $this->assertIdentical($actual_json, Json::encode($expected), 'The expected JSON output was found.');
+    $this->assertIdentical($actual_json, json_encode($expected), 'The expected JSON output was found.');
 
 
     // Test that the rendered output and the preview output are the same.
diff --git a/core/modules/serialization/lib/Drupal/serialization/Tests/EntitySerializationTest.php b/core/modules/serialization/lib/Drupal/serialization/Tests/EntitySerializationTest.php
index 1cc96cc..262d0a6 100644
--- a/core/modules/serialization/lib/Drupal/serialization/Tests/EntitySerializationTest.php
+++ b/core/modules/serialization/lib/Drupal/serialization/Tests/EntitySerializationTest.php
@@ -13,7 +13,6 @@
 use Drupal\serialization\Normalizer\TypedDataNormalizer;
 use Drupal\simpletest\DrupalUnitTestBase;
 use Symfony\Component\Serializer\Serializer;
-use Drupal\Component\Utility\Json;
 
 /**
  * Tests entity normalization and serialization of supported core formats.
@@ -122,7 +121,7 @@ public function testSerialize() {
     // JsonEncoder. The output of ComplexDataNormalizer::normalize() is tested
     // elsewhere, so we can just assume that it works properly here.
     $normalized = $this->serializer->normalize($this->entity, 'json');
-    $expected = Json::encode($normalized);
+    $expected = json_encode($normalized);
     // Test 'json'.
     $actual = $this->serializer->serialize($this->entity, 'json');
     $this->assertIdentical($actual, $expected, 'Entity serializes to JSON when "json" is requested.');
diff --git a/core/modules/system/tests/modules/ajax_test/ajax_test.module b/core/modules/system/tests/modules/ajax_test/ajax_test.module
index b7ab7a1..2ea9eb9 100644
--- a/core/modules/system/tests/modules/ajax_test/ajax_test.module
+++ b/core/modules/system/tests/modules/ajax_test/ajax_test.module
@@ -5,7 +5,6 @@
  * Helper module for Ajax framework tests.
  */
 
-use Drupal\Component\Utility\Json;
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\AlertCommand;
 use Drupal\Core\Ajax\OpenDialogCommand;
@@ -131,7 +130,7 @@ function ajax_test_dialog() {
         'attributes' => array(
           'class' => array('use-ajax'),
           'data-accepts' => 'application/vnd.drupal-modal',
-          'data-dialog-options' => Json::encode(array(
+          'data-dialog-options' => json_encode(array(
             'width' => 400,
           ))
         ),
@@ -142,7 +141,7 @@ function ajax_test_dialog() {
         'attributes' => array(
           'class' => array('use-ajax'),
           'data-accepts' => 'application/vnd.drupal-dialog',
-          'data-dialog-options' => Json::encode(array(
+          'data-dialog-options' => json_encode(array(
             'target' => 'ajax-test-dialog-wrapper-1',
             'width' => 800,
           ))
@@ -169,7 +168,7 @@ function ajax_test_dialog() {
         'attributes' => array(
           'class' => array('use-ajax'),
           'data-accepts' => 'application/vnd.drupal-modal',
-          'data-dialog-options' => Json::encode(array(
+          'data-dialog-options' => json_encode(array(
             'width' => 800,
             'height' => 500,
           ))
@@ -181,7 +180,7 @@ function ajax_test_dialog() {
         'attributes' => array(
           'class' => array('use-ajax'),
           'data-accepts' => 'application/vnd.drupal-dialog',
-          'data-dialog-options' => Json::encode(array(
+          'data-dialog-options' => json_encode(array(
             'width' => 800,
           ))
         ),