diff --git a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
index 146ee97..54018c7 100644
--- a/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
+++ b/core/lib/Drupal/Core/Installer/Form/SiteConfigureForm.php
@@ -190,6 +190,8 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#options' => $countries,
       '#description' => $this->t('Select the default country for the site.'),
       '#weight' => 0,
+      // Use the Select2 library.
+      '#select2' => TRUE,
     );
     $form['regional_settings']['date_default_timezone'] = array(
       '#type' => 'select',
diff --git a/core/modules/entity_reference/src/Plugin/Field/FieldWidget/AutocompleteWidgetBase.php b/core/modules/entity_reference/src/Plugin/Field/FieldWidget/AutocompleteWidgetBase.php
index b392f45..23063fc 100644
--- a/core/modules/entity_reference/src/Plugin/Field/FieldWidget/AutocompleteWidgetBase.php
+++ b/core/modules/entity_reference/src/Plugin/Field/FieldWidget/AutocompleteWidgetBase.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\Tags;
 use Drupal\Core\Field\EntityReferenceFieldItemListInterface;
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\Field\WidgetBase;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\user\EntityOwnerInterface;
@@ -87,6 +88,11 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
       $autocomplete_route_parameters['entity_id'] = $entity_id;
     }
 
+    $max_selection_size = $this->fieldDefinition->getFieldStorageDefinition()->getCardinality();
+    if ($max_selection_size === FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED) {
+      $max_selection_size = 0;
+    }
+
     $element += array(
       '#type' => 'textfield',
       '#maxlength' => 1024,
@@ -95,6 +101,7 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
       '#autocomplete_route_parameters' => $autocomplete_route_parameters,
       '#autocomplete_options' => array(
         'id_in_text' => TRUE,
+        'maximumSelectionSize' => $max_selection_size,
       ),
       '#size' => $this->getSetting('size'),
       '#placeholder' => $this->getSetting('placeholder'),
diff --git a/core/modules/node/src/Entity/Node.php b/core/modules/node/src/Entity/Node.php
index 4b7671f..fbffc46 100644
--- a/core/modules/node/src/Entity/Node.php
+++ b/core/modules/node/src/Entity/Node.php
@@ -378,6 +378,7 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setSetting('handler', 'default')
       ->setDefaultValueCallback('Drupal\node\Entity\Node::getCurrentUserId')
       ->setTranslatable(TRUE)
+//      ->setCardinality(1)
       ->setDisplayOptions('view', array(
         'label' => 'hidden',
         'type' => 'author',
diff --git a/core/modules/system/src/Form/RegionalForm.php b/core/modules/system/src/Form/RegionalForm.php
index 0550370..6e5b630 100644
--- a/core/modules/system/src/Form/RegionalForm.php
+++ b/core/modules/system/src/Form/RegionalForm.php
@@ -78,6 +78,8 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#default_value' => $system_date->get('country.default'),
       '#options' => $countries,
       '#attributes' => array('class' => array('country-detect')),
+      // Use the Select2 library.
+      '#select2' => TRUE,
     );
 
     $form['locale']['date_first_day'] = array(
diff --git a/core/modules/taxonomy/src/Plugin/Field/FieldWidget/TaxonomyAutocompleteWidget.php b/core/modules/taxonomy/src/Plugin/Field/FieldWidget/TaxonomyAutocompleteWidget.php
index dd85ed7..ae03524 100644
--- a/core/modules/taxonomy/src/Plugin/Field/FieldWidget/TaxonomyAutocompleteWidget.php
+++ b/core/modules/taxonomy/src/Plugin/Field/FieldWidget/TaxonomyAutocompleteWidget.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
 use Drupal\Core\Field\WidgetBase;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
@@ -110,6 +111,12 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
         $tags[] = isset($item->entity) ? $item->entity : $this->termStorage->load($item->target_id);
       }
     }
+
+    $max_selection_size = $this->fieldDefinition->getFieldStorageDefinition()->getCardinality();
+    if ($max_selection_size === FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED) {
+      $max_selection_size = 0;
+    }
+
     $element += array(
       '#type' => 'textfield',
       '#default_value' => taxonomy_implode_tags($tags),
@@ -118,6 +125,9 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
         'entity_type' => $items->getEntity()->getEntityTypeId(),
         'field_name' => $this->fieldDefinition->getName(),
       ),
+      '#autocomplete_options' => array(
+        'maximumSelectionSize' => $max_selection_size,
+      ),
       '#size' => $this->getSetting('size'),
       '#placeholder' => $this->getSetting('placeholder'),
       '#maxlength' => 1024,