diff --git a/core/modules/media_library/css/media_library.theme.css b/core/modules/media_library/css/media_library.theme.css
index 03cc0fc766..92c52d69e1 100644
--- a/core/modules/media_library/css/media_library.theme.css
+++ b/core/modules/media_library/css/media_library.theme.css
@@ -88,13 +88,6 @@
   outline: none;
 }
 
-.media-library-add-form-input-wrapper {
-  padding: 16px;
-  border: 1px solid #bfbfbf;
-  border-radius: 2px;
-  background: #fcfcfa;
-}
-
 .media-library-add-form--without-input .form-item {
   margin: 0 0 1em;
 }
@@ -103,6 +96,13 @@
   outline: none;
 }
 
+.media-library-add-form__input-wrapper {
+  padding: 16px;
+  border: 1px solid #bfbfbf;
+  border-radius: 2px;
+  background: #fcfcfa;
+}
+
 /* Style the media add upload form. */
 .media-library-add-form--upload.media-library-add-form--without-input .form-item-upload {
   margin-bottom: 0;
@@ -113,12 +113,12 @@
 }
 
 /* Style the media add oEmbed form. */
-.media-library-add-form--oembed .media-library-add-form-input-wrapper {
+.media-library-add-form--oembed .media-library-add-form__input-wrapper {
   display: flex;
 }
 
 @media screen and (max-width: 37.5em) {
-  .media-library-add-form--oembed .media-library-add-form-input-wrapper {
+  .media-library-add-form--oembed .media-library-add-form__input-wrapper {
     display: block;
   }
 }
diff --git a/core/modules/media_library/src/Form/AddFormBase.php b/core/modules/media_library/src/Form/AddFormBase.php
index 9139fd4345..d5ec0f16f1 100644
--- a/core/modules/media_library/src/Form/AddFormBase.php
+++ b/core/modules/media_library/src/Form/AddFormBase.php
@@ -110,6 +110,8 @@ protected function getMediaType(FormStateInterface $form_state) {
    * {@inheritdoc}
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
+    // @todo Remove the ID when we can use selectors to replace content via
+    //   AJAX in https://www.drupal.org/project/drupal/issues/2821793.
     $form['#prefix'] = '<div id="media-library-add-form-wrapper" class="media-library-add-form-wrapper">';
     $form['#suffix'] = '</div>';
     $form['#attached']['library'][] = 'media_library/style';
@@ -210,7 +212,7 @@ protected function buildEntityFormElement(MediaInterface $media, array $form, Fo
       ],
       'preview' => [
         '#type' => 'container',
-        '#weight' => 1,
+        '#weight' => 10,
         '#attributes' => [
           'class' => [
             'media-library-add-form__preview',
@@ -219,7 +221,7 @@ protected function buildEntityFormElement(MediaInterface $media, array $form, Fo
       ],
       'fields' => [
         '#type' => 'container',
-        '#weight' => 2,
+        '#weight' => 20,
         '#attributes' => [
           'class' => [
             'media-library-add-form__fields',
@@ -233,7 +235,7 @@ protected function buildEntityFormElement(MediaInterface $media, array $form, Fo
         '#type' => 'submit',
         '#value' => $this->t('Remove'),
         '#name' => 'media-' . $delta . '-remove-button' . $id_suffix,
-        '#weight' => 3,
+        '#weight' => 30,
         '#attributes' => [
           'class' => ['media-library-add-form__remove-button'],
           'aria-label' => $this->t('Remove @label', ['@label' => $media->getName()]),
@@ -441,7 +443,7 @@ public function updateFormCallback(array &$form, FormStateInterface $form_state)
     // Update the form and shift focus to the added media items.
     else {
       $response->addCommand(new ReplaceCommand("#$wrapper_id", $form));
-      $response->addCommand(new InvokeCommand('#media-library-add-form-wrapper .media-library-add-form__added-media', 'focus'));
+      $response->addCommand(new InvokeCommand('.media-library-add-form__added-media', 'focus'));
     }
 
     return $response;
diff --git a/core/modules/media_library/src/Form/FileUploadForm.php b/core/modules/media_library/src/Form/FileUploadForm.php
index 97cf08fe73..283ae74e97 100644
--- a/core/modules/media_library/src/Form/FileUploadForm.php
+++ b/core/modules/media_library/src/Form/FileUploadForm.php
@@ -122,11 +122,11 @@ protected function buildInputElement(array $form, FormStateInterface $form_state
 
     $slots = $state->getAvailableSlots();
 
-    // Add a container to group the input elements.
+    // Add a container to group the input elements for styling purposes.
     $form['container'] = [
       '#type' => 'container',
       '#attributes' => [
-        'class' => ['media-library-add-form-input-wrapper'],
+        'class' => ['media-library-add-form__input-wrapper'],
       ],
     ];
 
diff --git a/core/modules/media_library/src/Form/OEmbedForm.php b/core/modules/media_library/src/Form/OEmbedForm.php
index ec543b0fbb..4af94334c0 100644
--- a/core/modules/media_library/src/Form/OEmbedForm.php
+++ b/core/modules/media_library/src/Form/OEmbedForm.php
@@ -91,11 +91,11 @@ protected function buildInputElement(array $form, FormStateInterface $form_state
     $media_type = $this->getMediaType($form_state);
     $providers = $media_type->getSource()->getProviders();
 
-    // Add a container to group the input elements.
+    // Add a container to group the input elements for styling purposes.
     $form['container'] = [
       '#type' => 'container',
       '#attributes' => [
-        'class' => ['media-library-add-form-input-wrapper'],
+        'class' => ['media-library-add-form__input-wrapper'],
       ],
     ];
 
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
index f8003b6e90..7fbc75b2ce 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/MediaLibraryTest.php
@@ -832,7 +832,7 @@ public function testWidgetUpload() {
     $page->attachFileToField('Add files', $this->container->get('file_system')->realpath($png_image->uri));
     $assert_session->assertWaitOnAjaxRequest();
     // Assert the focus is shifted to the added media items.
-    $this->assertJsCondition('jQuery("#media-library-add-form-wrapper .media-library-add-form__added-media").is(":focus")');
+    $this->assertJsCondition('jQuery(".media-library-add-form__added-media").is(":focus")');
     // Assert the media item fields are shown and the vertical tabs are no
     // longer shown.
     $assert_session->elementExists('css', '.media-library-add-form__fields');
@@ -842,8 +842,7 @@ public function testWidgetUpload() {
     $assert_session->elementExists('css', '.media-library-add-form__remove-button')->click();
     $assert_session->assertWaitOnAjaxRequest();
     // Assert the remove message is shown.
-    $filename = $png_image->filename;
-    $assert_session->pageTextContains("The media item $filename has been removed.");
+    $assert_session->pageTextContains("The media item $png_image->filename has been removed.");
     // Assert the focus is shifted to the first tabbable element of the add
     // form, which should be the source field.
     $this->assertJsCondition('jQuery("#media-library-add-form-wrapper :tabbable").is(":focus")');
@@ -949,7 +948,7 @@ public function testWidgetOEmbed() {
     $assert_session->pageTextNotContains('Add or select media');
     $assert_session->pageTextContains('Custom video title');
 
-    // Assert removing an uploaded media item before save works as expected.
+    // Assert removing an added oEmbed media item before save works as expected.
     $assert_session->elementExists('css', '.media-library-open-button[name^="field_unlimited_media"]')->click();
     $assert_session->assertWaitOnAjaxRequest();
     $assert_session->pageTextContains('Add or select media');
@@ -959,7 +958,7 @@ public function testWidgetOEmbed() {
     $page->pressButton('Add');
     $assert_session->assertWaitOnAjaxRequest();
     // Assert the focus is shifted to the added media items.
-    $this->assertJsCondition('jQuery("#media-library-add-form-wrapper .media-library-add-form__added-media").is(":focus")');
+    $this->assertJsCondition('jQuery(".media-library-add-form__added-media").is(":focus")');
     // Assert the media item fields are shown and the vertical tabs are no
     // longer shown.
     $assert_session->elementExists('css', '.media-library-add-form__fields');