diff --git a/core/modules/content_translation/content_translation.admin.inc b/core/modules/content_translation/content_translation.admin.inc
index f509752..306cbbd 100644
--- a/core/modules/content_translation/content_translation.admin.inc
+++ b/core/modules/content_translation/content_translation.admin.inc
@@ -144,116 +144,88 @@ function _content_translation_form_language_content_settings_form_alter(array &$
  * (proxied) Implements hook_preprocess_HOOK();
  */
 function _content_translation_preprocess_language_content_settings_table(&$variables) {
-  // Alter the 'build' variable injecting the translation settings if the user
+  // Alter the 'table' variable injecting the translation settings if the user
   // has the required permission.
   if (!user_access('administer content translation')) {
     return;
   }
 
   $element = $variables['element'];
-  $build = &$variables['build'];
+  $table = &$variables['table'];
 
-  array_unshift($build['#header'], array('data' => t('Translatable'), 'class' => array('translatable')));
-  $rows = array();
+  array_unshift($table['#header'], array('data' => t('Translatable'), 'class' => array('translatable')));
 
   foreach (element_children($element) as $bundle) {
     $field_names = !empty($element[$bundle]['fields']) ? element_children($element[$bundle]['fields']) : array();
     if (!empty($element[$bundle]['translatable'])) {
       $checkbox_id = $element[$bundle]['translatable']['#id'];
     }
-    $rows[$bundle] = $build['#rows'][$bundle];
 
     if (!empty($element[$bundle]['translatable'])) {
-      $translatable = array(
-        'data' => $element[$bundle]['translatable'],
-        'class' => array('translatable'),
-      );
-      array_unshift($rows[$bundle]['data'], $translatable);
-
-      $rows[$bundle]['data'][1]['data']['#prefix'] = '<label for="' . $checkbox_id . '">';
+      $translatable = $element[$bundle]['translatable'];
+      $translatable['#wrapper_attributes'] = array('class' => array('translatable'));
+      $table[$bundle]['label']['#prefix'] = '<label for="' . $checkbox_id . '">';
     }
     else {
-      $translatable = array(
-        'class' => array('untranslatable'),
-      );
-      array_unshift($rows[$bundle]['data'], $translatable);
+      $translatable = array();
+      $translatable['#wrapper_attributes'] = array('class' => array('translatable'));
     }
+    array_unshift($table[$bundle], $translatable);
 
     foreach ($field_names as $field_name) {
       $field_element = &$element[$bundle]['fields'][$field_name];
-      $rows[] = array(
-        'data' => array(
-          array(
-            'data' => drupal_render($field_element),
-            'class' => array('translatable'),
-          ),
-          array(
-            'data' => array(
-              '#prefix' => '<label for="' . $field_element['#id'] . '">',
-              '#suffix' => '</label>',
-              'bundle' => array(
-                '#prefix' => '<span class="visually-hidden">',
-                '#suffix' => '</span> ',
-                '#markup' => check_plain($element[$bundle]['settings']['#label']),
-              ),
-              'field' => array(
-                '#markup' => check_plain($field_element['#label']),
-              ),
-            ),
-            'class' => array('field'),
-          ),
-          array(
-            'data' => '',
-            'class' => array('operations'),
-          ),
+
+      $table[$field_name]['translatable'] = $field_element;
+      $table[$field_name]['translatable']['#wrapper_attributes'] = array('class' => array('translatable'));
+      $table[$field_name]['label'] = array(
+        '#wrapper_attributes' => array('class' => array('field-settings')),
+        '#prefix' => '<label for="' . $field_element['#id'] . '">',
+        '#suffix' => '</label>',
+        'bundle' => array(
+          '#prefix' => '<span class="visually-hidden">',
+          '#suffix' => '</span> ',
+          '#markup' => check_plain($element[$bundle]['settings']['#label']),
+        ),
+        'field' => array(
+          '#markup' => check_plain($field_element['#label']),
         ),
-        'class' => array('field-settings'),
       );
+      $table[$field_name]['operations'] = array();
+      $table[$field_name]['operations']['#wrapper_attributes'] = array('class' => array('operations'));
 
       if (!empty($element[$bundle]['columns'][$field_name])) {
         $column_element = &$element[$bundle]['columns'][$field_name];
         foreach (element_children($column_element) as $key) {
           $column_label = $column_element[$key]['#title'];
           unset($column_element[$key]['#title']);
-          $rows[] = array(
-            'data' => array(
-              array(
-                'data' => drupal_render($column_element[$key]),
-                'class' => array('translatable'),
-              ),
-              array(
-                'data' => array(
-                  '#prefix' => '<label for="' . $column_element[$key]['#id'] . '">',
-                  '#suffix' => '</label>',
-                  'bundle' => array(
-                    '#prefix' => '<span class="visually-hidden">',
-                    '#suffix' => '</span> ',
-                    '#markup' => check_plain($element[$bundle]['settings']['#label']),
-                  ),
-                  'field' => array(
-                    '#prefix' => '<span class="visually-hidden">',
-                    '#suffix' => '</span> ',
-                    '#markup' => check_plain($field_element['#label']),
-                  ),
-                  'columns' => array(
-                    '#markup' => check_plain($column_label),
-                  ),
-                ),
-                'class' => array('column'),
-              ),
-              array(
-                'data' => '',
-                'class' => array('operations'),
-              ),
+
+          $table[$key]['#attributes'] = array('class' => array('column-settings'));
+          $table[$key]['translatable'] = $column_element[$key];
+          $table[$key]['translatable']['#wrapper_attributes'] = array('class' => array('translatable'));
+          $table[$key]['label'] = array(
+            '#wrapper_attributes' => array('class' => array('column')),
+            '#prefix' => '<label for="' . $column_element[$key]['#id'] . '">',
+            '#suffix' => '</label>',
+            'bundle' => array(
+              '#prefix' => '<span class="visually-hidden">',
+              '#suffix' => '</span> ',
+              '#markup' => check_plain($element[$bundle]['settings']['#label']),
+            ),
+            'field' => array(
+              '#prefix' => '<span class="visually-hidden">',
+              '#suffix' => '</span> ',
+              '#markup' => check_plain($field_element['#label']),
+            ),
+            'columns' => array(
+              '#markup' => check_plain($column_label),
             ),
-            'class' => array('column-settings'),
           );
+          $table[$key]['operations'] = array();
+          $table[$key]['operations']['#wrapper_attributes'] = array('class' => array('operations'));
         }
       }
     }
   }
-
-  $build['#rows'] = $rows;
 }
 
 /**
diff --git a/core/modules/language/language.admin.inc b/core/modules/language/language.admin.inc
index 79dc5d1..52ca03e 100644
--- a/core/modules/language/language.admin.inc
+++ b/core/modules/language/language.admin.inc
@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Language\LanguageManager;
+use Drupal\Component\Utility\String;
 
 /**
  * Prepare a language code list for unused predefined languages.
@@ -27,75 +28,84 @@ function language_admin_predefined_list() {
 /**
  * Returns HTML for the language negotiation configuration form.
  *
- * @param $variables
+ * Default template: language-content-configuration-form.html.twig.
+ *
+ * @param array $variables
  *   An associative array containing:
  *   - form: A render element representing the form.
- *
- * @ingroup themeable
  */
-function theme_language_negotiation_configure_form($variables) {
-  $form = $variables['form'];
-  $output = '';
+function template_preprocess_language_negotiation_configure_form(&$variables) {
+  $form =& $variables['form'];
+  $variables['language_types'] = array();
 
   foreach ($form['#language_types'] as $type) {
-    $rows = array();
-    $title = '<h4 class="label">' . $form[$type]['#title'] . '</h4>';
-    $description = '<div class="description">' . $form[$type]['#description'] . '</div>';
-
-    foreach ($form[$type]['title'] as $id => $element) {
-      // Do not take form control structures.
-      if (is_array($element) && element_child($id)) {
-        $row = array(
-          'data' => array(
-            '<strong>' . drupal_render($form[$type]['title'][$id]) . '</strong>',
-            drupal_render($form[$type]['description'][$id]),
-            drupal_render($form[$type]['enabled'][$id]),
-            drupal_render($form[$type]['weight'][$id]),
-          ),
-          'class' => array('draggable'),
-        );
-        if ($form[$type]['#show_operations']) {
-          $row['data'][] = drupal_render($form[$type]['operation'][$id]);
-        }
-        $rows[] = $row;
-      }
-    }
-
     $header = array(
-      array('data' => t('Detection method')),
-      array('data' => t('Description')),
-      array('data' => t('Enabled')),
-      array('data' => t('Weight')),
+      t('Detection method'),
+      t('Description'),
+      t('Enabled'),
+      t('Weight'),
     );
 
     // If there is at least one operation enabled show the operation column.
     if ($form[$type]['#show_operations']) {
-      $header[] = array('data' => t('Operations'));
+      $header[] = t('Operations');
     }
 
-    $build = array(
+    $table = array(
       '#type' => 'table',
       '#header' => $header,
-      '#rows' => $rows,
-      '#attributes' => array('id' => "language-negotiation-methods-$type"),
+      '#attributes' => array('id' => 'language-negotiation-methods-' . $type),
       '#tabledrag' => array(
         array(
           'action' => 'order',
           'relationship' => 'sibling',
-          'group' => "language-method-weight-$type",
+          'group' => 'language-method-weight-' . $type,
         ),
       ),
     );
 
-    $table  = drupal_render($form[$type]['configurable']);
-    $table .= drupal_render($build);
-    $table .= drupal_render_children($form[$type]);
+    foreach ($form[$type]['title'] as $id => $element) {
+      // Do not take form control structures.
+      if (is_array($element) && element_child($id)) {
+        $table[$id]['#attributes']['class'][] = 'draggable';
+        $table[$id]['#weight'] = $element['#weight'];
+
+        $table[$id]['title'] = array(
+          '#prefix' => '<strong>',
+          $form[$type]['title'][$id],
+          '#suffix' => '</strong>',
+        );
+        $table[$id]['description'] = $form[$type]['description'][$id];
+        $table[$id]['enabled'] = $form[$type]['enabled'][$id];
+        $table[$id]['weight'] = $form[$type]['weight'][$id];
+        if ($form[$type]['#show_operations']) {
+          $table[$id]['operation'] = $form[$type]['operation'][$id];
+        }
+        // Unset so we don't print them along with children as well.
+        unset($form[$type]['title'][$id]);
+        unset($form[$type]['description'][$id]);
+        unset($form[$type]['enabled'][$id]);
+        unset($form[$type]['weight'][$id]);
+        unset($form[$type]['operation'][$id]);
+      }
+    }
 
-    $output .= '<div class="form-item table-language-group table-' . $type . '-wrapper">' . $title . $description . $table . '</div>';
+    // Store and unset configurable so it doesn't print twice in form children.
+    $configurable = isset($form[$type]['configurable']) ? $form[$type]['configurable'] : NULL;
+    unset($form[$type]['configurable']);
+
+    $variables['language_types'][] = array(
+      'type' => $type,
+      'title' => $form[$type]['#title'],
+      'description' => $form[$type]['#description'],
+      'configurable' => $configurable,
+      'table' => $table,
+      'children' => $form[$type],
+    );
+    unset($form[$type]);
   }
 
-  $output .= drupal_render_children($form);
-  return $output;
+  $variables['children'] = $form;
 }
 
 /**
@@ -248,64 +258,44 @@ function language_content_settings_form(array $form, array $form_state, array $s
 }
 
 /**
- * Implements hook_preprocess_HOOK() for theme_language_content_settings_table().
+ * Prepares variables for language content settings table templates.
+ *
+ * Default template: language-content-settings-table.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - @todo list variables.
  */
 function template_preprocess_language_content_settings_table(&$variables) {
   // Add a render element representing the bundle language settings table.
   $element = $variables['element'];
 
-  $header = array(
-    array(
-      'data' => $element['#bundle_label'],
-      'class' => array('bundle'),
-    ),
-    array(
-      'data' => t('Configuration'),
-      'class' => array('operations'),
+  $variables['table'] = array(
+    '#type' => 'table',
+    '#header' => array(
+      array(
+        'data' => $element['#bundle_label'],
+        'class' => array('bundle'),
+      ),
+      array(
+        'data' => t('Configuration'),
+        'class' => array('operations'),
+      ),
     ),
   );
 
-  $rows = array();
   foreach (element_children($element) as $bundle) {
-    $rows[$bundle] = array(
-      'data' => array(
-        array(
-          'data' => array(
-            '#prefix' => '<label>',
-            '#suffix' => '</label>',
-            '#markup' => check_plain($element[$bundle]['settings']['#label']),
-          ),
-          'class' => array('bundle'),
-        ),
-        array(
-          'data' => $element[$bundle]['settings'],
-          'class' => array('operations'),
-        ),
-      ),
-      'class' => array('bundle-settings'),
+    $variables['table'][$bundle]['#attributes']['class'][] = 'bundle-settings';
+    $variables['table'][$bundle]['label'] = array(
+      '#wrapper_attributes' => array('class' => array('bundle')),
+      '#prefix' => '<label>',
+      '#suffix' => '</label>',
+      '#markup' => String::checkPlain($element[$bundle]['settings']['#label']),
     );
+    $variables['table'][$bundle]['operations'] = $element[$bundle]['settings'];
+    $variables['table'][$bundle]['operations']['#wrapper_attributes'] = array('class' => array('operations'));
   }
-
-  $variables['build'] = array(
-    '#title' => $element['#title'],
-    '#header' => $header,
-    '#rows' => $rows,
-    '#theme' => 'table',
-  );
-}
-
-/**
- * Returns HTML for an administration settings table.
- *
- * @param array $variables
- *   An associative array containing:
- *   - build: A render element representing a table of bundle content language
- *     settings for a particular entity type.
- *
- * @ingroup themable
- */
-function theme_language_content_settings_table($variables) {
-  return '<h4>' . $variables['build']['#title'] . '</h4>' . drupal_render($variables['build']);
+  $variables['title'] = $element['#title'];
 }
 
 /**
diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 883ab88..5338ac6 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -122,10 +122,12 @@ function language_theme() {
     'language_negotiation_configure_browser_form_table' => array(
       'render element' => 'form',
       'file' => 'language.admin.inc',
+      'template' => 'language-negotiation-configure-form',
     ),
     'language_content_settings_table' => array(
       'render element' => 'element',
       'file' => 'language.admin.inc',
+      'template' => 'language-content-settings-table',
     ),
   );
 }
diff --git a/core/modules/language/lib/Drupal/language/Form/NegotiationBrowserForm.php b/core/modules/language/lib/Drupal/language/Form/NegotiationBrowserForm.php
index 0537a6a..2fd079c 100644
--- a/core/modules/language/lib/Drupal/language/Form/NegotiationBrowserForm.php
+++ b/core/modules/language/lib/Drupal/language/Form/NegotiationBrowserForm.php
@@ -82,11 +82,25 @@ public function buildForm(array $form, array &$form_state) {
 
     $form['mappings'] = array(
       '#tree' => TRUE,
-      '#theme' => 'language_negotiation_configure_browser_form_table',
+      '#type' => 'table',
+      '#header' => array(
+        t('Browser language code'),
+        t('Drupal language'),
+        t('Operations'),
+      ),
+      '#attributes' => array('id' => 'lang-neg-browser'),
     );
 
     $mappings = $this->language_get_browser_drupal_langcode_mappings();
     foreach ($mappings as $browser_langcode => $drupal_langcode) {
+      $links = array();
+      $links['delete'] = array(
+        'title' => t('Delete'),
+        'href' => 'admin/config/regional/language/detection/browser/delete/' . $browser_langcode,
+        'attributes' => array(
+          'class' => array('image-style-link'),
+        ),
+      );
       $form['mappings'][$browser_langcode] = array(
         'browser_langcode' => array(
           '#type' => 'textfield',
@@ -100,6 +114,10 @@ public function buildForm(array $form, array &$form_state) {
           '#default_value' => $drupal_langcode,
           '#required' => TRUE,
         ),
+        'operations' => array(
+          '#type' => 'operations',
+          '#links' => $links,
+        ),
       );
     }
 
diff --git a/core/modules/language/templates/language-content-settings-table.html.twig b/core/modules/language/templates/language-content-settings-table.html.twig
new file mode 100644
index 0000000..2c7a61a
--- /dev/null
+++ b/core/modules/language/templates/language-content-settings-table.html.twig
@@ -0,0 +1,18 @@
+{#
+/**
+* @file
+* Default theme implementation for an administration settings table.
+*
+* Available variables:
+* - title: A title for the table
+* - attributes: Remaining HTML attributes for the element.
+* - table: A render element representing a table of bundle content language
+*    settings for a particular entity type.
+*
+* @see template_preprocess_language_content_settings_table()
+*
+* @ingroup themeable
+*/
+#}
+<h4>{{ title }}</h4>
+{{ table }}
diff --git a/core/modules/language/templates/language-negotiation-configure-form.html.twig b/core/modules/language/templates/language-negotiation-configure-form.html.twig
new file mode 100644
index 0000000..1da8a3e
--- /dev/null
+++ b/core/modules/language/templates/language-negotiation-configure-form.html.twig
@@ -0,0 +1,30 @@
+{#
+/**
+* @file
+* Default theme implementation for a language negotiation configuration form.
+*
+* Available variables:
+* - language_types: @todo.
+*   - type: @todo.
+*   - title: @todo.
+*   - description: @todo.
+*   - configurable: @todo.
+*   - table: @todo.
+*   - children: @todo.
+* - children: Remaining form items like the save button.
+*
+* @see template_preprocess_language_negotiation_configure_form()
+*
+* @ingroup themeable
+*/
+#}
+{% for language_type in language_types %}
+  <div class="form-item table-language-group table-{{ language_type.type }}-wrapper">
+    <h4 class="label">{{ language_type.title }}</h4>
+    <div class="description">{{ language_type.description }}</div>
+    {{ language_type.configurable }}
+    {{ language_type.table }}
+    {{ language_type.children }}
+  </div>
+{% endfor %}
+{{ form }}