diff -u b/core/misc/ajax.js b/core/misc/ajax.js
--- b/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -1015,10 +1015,6 @@
      *   The XMLHttpRequest status.
      */
     insert: function (ajax, response, status) {
-      if (!response.data) {
-        return;
-      }
-
       // Get information from the response. If it is not there, default to
       // our presets.
       var $wrapper = response.selector ? $(response.selector) : $(ajax.wrapper);
@@ -1036,25 +1032,37 @@
       // will be wrapped with a <span> element. This also gives themers the
       // possibility to style the response.
       var $new_content;
+      var onlyElementNodes;
+      var trimedData = response.data.trim();
 
-      // If only NODE_ELEMENT or COMMENT_NODE elements are returned skip wrap processing.
-      var responseDataWrappedContents = $.parseHTML(response.data.trim(), true);
-      var isAllElementNode = responseDataWrappedContents.every(function (element) {
-        return element.nodeType === Node.ELEMENT_NODE || element.nodeType === Node.COMMENT_NODE;
-      });
+      // Tranform the response data in an array of DOM Nodes.
+      var responseDataNodes = $.parseHTML(trimedData, true);
+      // When response.data is empty (to empty an element for exemple)
+      // parseHTML returns null, we need to cheat a little.
+      if (responseDataNodes === null && trimedData === '') {
+        onlyElementNodes = false;
+        responseDataNodes = [''];
+      }
+      else {
+        onlyElementNodes = responseDataNodes.every(function (element) {
+          return element.nodeType === Node.ELEMENT_NODE || element.nodeType === Node.COMMENT_NODE;
+        });
+      }
 
-      if (!isAllElementNode) {
-        // If response.data contains TEXT_ELEMENT type only or target element
-        // is not a block level element, response.data will be wrapped with SPAN.
-        if (responseDataWrappedContents.length === 1 || ($wrapper.css('display') !== 'block')) {
-          $new_content = $('<span class="ajax-inline"></span>').html(response.data);
+      // If only NODE_ELEMENT or COMMENT_NODE elements are returned skip wrap processing.
+      if (!onlyElementNodes) {
+        // If response.data contains only one TEXT_ELEMENT if the target element
+        // is not styled as a block, response.data will be wrapped with SPAN.
+        if (responseDataNodes.length === 1 || ($wrapper.css('display') !== 'block')) {
+          $new_content = $('<span></span>');
         }
         else {
-          $new_content = $('<div></div>').html(response.data);
+          $new_content = $('<div></div>');
         }
+        $new_content.html(responseDataNodes);
       }
       else {
-        $new_content = $(response.data);
+        $new_content = $(responseDataNodes);
       }
 
       // If removing content from the wrapper, detach behaviors first.
@@ -1065,10 +1073,7 @@
         case 'empty':
         case 'remove':
           settings = response.settings || ajax.settings || drupalSettings;
-          // Detach behaviors of all the to be removed element nodes.
-          $wrapper.children().each(function () {
-            Drupal.detachBehaviors(this, settings);
-          });
+          Drupal.detachBehaviors($wrapper.get(0), settings);
       }
 
       // Add the new content to the page.
diff -u b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
--- b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
+++ b/core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php
@@ -74,7 +74,7 @@
 
     $build['links'] = [
       'ajax_target' => [
-        '#markup' => '<div id="ajax-target">Target</div><div><strong>Inline Test:</strong></div><span>TEXT</span> <span id="ajax-target-inline"></span> <span>TEXT</span>',
+        '#markup' => '<div id="ajax-target" data-drupal-ajax-target="">Target</div><span id="ajax-target-inline" data-drupal-ajax-target="">Target inline</span>',
       ],
       'links' => [
         '#theme' => 'links',
diff -u b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
--- b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
@@ -17,16 +17,16 @@
   public static $modules = ['ajax_test'];
 
   /**
-   * Wrap HTML with an AJAX target div.
+   * Wrap HTML with an AJAX target element.
    *
    * @param string $html
    *   The HTML to wrap.
    *
    * @return string
-   *   The HTML wrapped in the an AJAX target div.
+   *   The HTML wrapped in the an AJAX target element.
    */
   protected function wrapAjaxTarget($html) {
-    return '<div id="ajax-target">' . $html . '</div>';
+    return 'data-drupal-ajax-target="">' . $html . '</';
   }
 
   public function testAjaxWithAdminRoute() {
@@ -104,7 +104,6 @@
    */
   public function testInsert() {
     $assert = $this->assertSession();
-
     $test_cases = [
       // Test that no additional wrapper is added when inserting already wrapped
       // response data and all top-level node elements (context) are processed
@@ -118,13 +117,13 @@
       // processed correctly.
       [
         'render_type' => 'pre-wrapped-whitespace',
-        'expected' => '<div class="pre-wrapped-whitespace processed">pre-wrapped-leading-whitespace</div>',
+        'expected' => '<div class="pre-wrapped-whitespace processed">pre-wrapped-whitespace</div>',
       ],
       // Test that not wrapped response data (text node) is inserted wrapped and
       // all top-level node elements (context) are processed correctly.
       [
         'render_type' => 'not-wrapped',
-        'expected' => '<span class="ajax-inline processed">not-wrapped</span>',
+        'expected' => '<span class="processed">not-wrapped</span>',
       ],
       // Test that top-level comments (which are not lead by text nodes) are
       // inserted without wrapper.
@@ -137,36 +136,34 @@
       [
         'method' => 'html',
         'render_type' => 'mixed',
-        'expected' => '<div class="processed"> foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p></div>',
+        'expected' => '<div class="processed">foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p></div>',
       ],
       // Test that inline response data.
       [
         'render_type' => 'inline',
-        'expected' => '<span class="ajax-inline processed">inline <div>BLOCK LEVEL<script> var test;</script></div></span>',
+        'expected' => '<span class="processed">inline <div>BLOCK LEVEL<script> var test;</script></div></span>',
       ],
       // Test that empty response data.
       [
         'render_type' => 'empty',
-        'expected' => '',
+        'expected' => '<span class="processed"></span>',
       ],
     ];
 
-    foreach (['html', 'replaceWith'] as $method) {
-      foreach ($test_cases as $test_case) {
-        $this->drupalGet('ajax-test/insert');
-        $this->clickLink("Link $method {$test_case['render_type']}");
-        $assert->assertWaitOnAjaxRequest();
-        switch ($method) {
-          case 'html':
-            $assert->responseContains($this->wrapAjaxTarget($test_case['expected']));
-            break;
-
-          case 'replaceWith':
-            $assert->responseContains($test_case['expected']);
-            $assert->responseNotContains($this->wrapAjaxTarget($test_case['expected']));
-            break;
-        }
-      }
+    $this->drupalGet('ajax-test/insert');
+    foreach ($test_cases as $test_case) {
+      $this->clickLink("Link html {$test_case['render_type']}");
+      $assert->assertWaitOnAjaxRequest();
+      // Extra span added by a second prepend command on the ajax requests.
+      $assert->responseContains($this->wrapAjaxTarget('<span class="processed"></span>' . $test_case['expected']));
+    }
+
+    foreach ($test_cases as $test_case) {
+      $this->drupalGet('ajax-test/insert');
+      $this->clickLink("Link replaceWith {$test_case['render_type']}");
+      $assert->assertWaitOnAjaxRequest();
+      $assert->responseContains($test_case['expected']);
+      $assert->responseNotContains($this->wrapAjaxTarget($test_case['expected']));
     }
   }