diff --git a/core/includes/form.inc b/core/includes/form.inc
index 77443ad..7cfd776 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -4071,17 +4071,13 @@ function theme_vertical_tabs($variables) {
 }
 
 /**
- * Adds autocomplete functionality to elements with a valid #autocomplete_path.
+ * Adds autocomplete functionality to elements with a valid
+ * #autocomplete_route_name.
  *
- * Suppose your autocomplete path in the menu system is 'mymodule_autocomplete.'
+ * Suppose your autocomplete route is 'mymodule.autocomplete.'
  * In your form you have:
  * @code
- * '#autocomplete_path' => 'mymodule_autocomplete/' . $some_key . '/' . $some_id,
- * @endcode
- * Or if your route is called 'mymodule_autocomplete' with the path of
- * '/mymodule-autocomplete/{a}/{b}':
- * @code
- * '#autocomplete_route_name' => 'mymodule_autocomplete',
+ * '#autocomplete_route_name' => 'mymodule.autocomplete',
  * '#autocomplete_route_parameters' => array('a' => $some_key, 'b' => $some_id),
  * @endcode
  * The user types in "keywords" so the full path called is:
@@ -4089,8 +4085,6 @@ function theme_vertical_tabs($variables) {
  *
  * @param array $element
  *   The form element to process. Properties used:
- *   - #autocomplete_path: A system path to be used as callback URL by the
- *     autocomplete JavaScript library.
  *   - #autocomplete_route_name: A route to be used as callback URL by the
  *     autocomplete JavaScript library.
  *   - #autocomplete_route_parameters: The parameters to be used in conjunction
@@ -4109,10 +4103,6 @@ function form_process_autocomplete($element, &$form_state) {
     $path = \Drupal::urlGenerator()->generate($element['#autocomplete_route_name'], $parameters);
     $access = \Drupal::service('access_manager')->checkNamedRoute($element['#autocomplete_route_name'], $parameters);
   }
-  elseif (!empty($element['#autocomplete_path'])) {
-    $path = url($element['#autocomplete_path'], array('absolute' => TRUE));
-    $access = drupal_valid_path($element['#autocomplete_path']);
-  }
   if ($access) {
     $element['#attributes']['class'][] = 'form-autocomplete';
     $element['#attached']['library'][] = array('system', 'drupal.autocomplete');
diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index 161c230..16a9138 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -238,7 +238,7 @@ function hook_field_widget_WIDGET_TYPE_form_alter(&$element, &$form_state, $cont
   // Code here will only act on widgets of type WIDGET_TYPE.  For example,
   // hook_field_widget_mymodule_autocomplete_form_alter() will only act on
   // widgets of type 'mymodule_autocomplete'.
-  $element['#autocomplete_path'] = 'mymodule/autocomplete_path';
+  $element['#autocomplete_route_name'] = 'mymodule.autocomplete_route';
 }
 
 /**
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 03f9042..84e3a4f 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -325,7 +325,7 @@ function system_element_info() {
     '#input' => TRUE,
     '#size' => 60,
     '#maxlength' => 128,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_autocomplete', 'ajax_process_form', 'form_process_pattern'),
     '#pre_render' => array('form_pre_render_textfield'),
     '#theme' => 'input__textfield',
@@ -335,7 +335,7 @@ function system_element_info() {
     '#input' => TRUE,
     '#size' => 30,
     '#maxlength' => 128,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_autocomplete', 'ajax_process_form', 'form_process_pattern'),
     '#pre_render' => array('form_pre_render_tel'),
     '#theme' => 'input__tel',
@@ -346,7 +346,7 @@ function system_element_info() {
     '#size' => 60,
     // user.module is not loaded in case of early bootstrap errors.
     '#maxlength' => defined('EMAIL_MAX_LENGTH') ? EMAIL_MAX_LENGTH : 255,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_autocomplete', 'ajax_process_form', 'form_process_pattern'),
     '#element_validate' => array('form_validate_email'),
     '#pre_render' => array('form_pre_render_email'),
@@ -357,7 +357,7 @@ function system_element_info() {
     '#input' => TRUE,
     '#size' => 60,
     '#maxlength' => 255,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_autocomplete', 'ajax_process_form', 'form_process_pattern'),
     '#element_validate' => array('form_validate_url'),
     '#pre_render' => array('form_pre_render_url'),
@@ -368,7 +368,7 @@ function system_element_info() {
     '#input' => TRUE,
     '#size' => 60,
     '#maxlength' => 128,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_autocomplete', 'ajax_process_form'),
     '#pre_render' => array('form_pre_render_search'),
     '#theme' => 'input__search',
@@ -408,7 +408,7 @@ function system_element_info() {
     '#required' => TRUE,
     '#maxlength' => 64,
     '#size' => 60,
-    '#autocomplete_path' => FALSE,
+    '#autocomplete_route_name' => FALSE,
     '#process' => array('form_process_machine_name', 'form_process_autocomplete', 'ajax_process_form'),
     '#element_validate' => array('form_validate_machine_name'),
     '#pre_render' => array('form_pre_render_textfield'),
diff --git a/core/modules/views_ui/lib/Drupal/views_ui/Form/Ajax/EditDetails.php b/core/modules/views_ui/lib/Drupal/views_ui/Form/Ajax/EditDetails.php
index 3c011f3..3a442b7 100644
--- a/core/modules/views_ui/lib/Drupal/views_ui/Form/Ajax/EditDetails.php
+++ b/core/modules/views_ui/lib/Drupal/views_ui/Form/Ajax/EditDetails.php
@@ -59,7 +59,7 @@ public function buildForm(array $form, array &$form_state) {
       '#title' => $this->t('View tag'),
       '#description' => $this->t('Optionally, enter a comma delimited list of tags for this view to use in filtering and sorting views on the administrative page.'),
       '#default_value' => $view->get('tag'),
-      '#autocomplete_path' => 'admin/views/ajax/autocomplete/tag',
+      '#autocomplete_route_name' => 'views_ui.autocomplete',
     );
     $form['details']['description'] = array(
       '#type' => 'textfield',