diff --git a/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php b/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php
index 963135acb5..7f5f8a34e1 100644
--- a/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php
+++ b/core/modules/media_library/src/Plugin/Field/FieldWidget/MediaLibraryWidget.php
@@ -46,11 +46,6 @@
  */
 class MediaLibraryWidget extends WidgetBase implements TrustedCallbackInterface {
 
-  /**
-   * The default media view mode when rendering already-selected media items.
-   */
-  const DEFAULT_VIEW_MODE = 'media_library';
-
   /**
    * Entity type manager service.
    *
@@ -464,7 +459,7 @@ public function formElement(FieldItemListInterface $items, $delta, array $elemen
           '#limit_validation_errors' => $limit_validation_errors,
         ],
         // @todo Make the view mode configurable in https://www.drupal.org/project/drupal/issues/2971209
-        'rendered_entity' => $view_builder->view($media_item, self::DEFAULT_VIEW_MODE),
+        'rendered_entity' => $view_builder->view($media_item, 'media_library'),
         'target_id' => [
           '#type' => 'hidden',
           '#value' => $media_item->id(),
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
index dea5f4e24c..351c12e6f6 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/EmbeddedFormWidgetTest.php
@@ -5,6 +5,7 @@
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
 use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+use Drupal\media_library\MediaLibraryState;
 use Drupal\Tests\TestFileCreationTrait;
 
 /**
@@ -70,7 +71,7 @@ protected function setUp(): void {
         'region' => 'content',
         'settings' => [
           'media_types' => ['type_three'],
-          'form_mode' => 'media_library',
+          'form_mode' => MediaLibraryState::DEFAULT_FORM_MODE,
         ],
       ])
       ->save();
@@ -104,7 +105,7 @@ public function testInsertionAndReselection($widget) {
         'region' => 'content',
         'settings' => [
           'media_types' => ['type_three'],
-          'form_mode' => 'media_library',
+          'form_mode' => MediaLibraryState::DEFAULT_FORM_MODE,
         ],
       ])
       ->save();
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/EntityReferenceWidgetTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/EntityReferenceWidgetTest.php
index 54de6cb25e..66afebff14 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/EntityReferenceWidgetTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/EntityReferenceWidgetTest.php
@@ -181,10 +181,10 @@ public function testWidget() {
     $this->assertSame($link_titles, $expected_link_titles);
     $this->drupalGet('admin/structure/types/manage/basic_page/form-display');
 
-    // Ensure that the widget settings form is not displayed when only
+    // Ensure that the widget settings form is displayed even when only
     // one media type is allowed.
     $assert_session->pageTextContains('Single media type');
-    $assert_session->buttonNotExists('field_single_media_type_settings_edit');
+    $assert_session->buttonExists('field_single_media_type_settings_edit');
 
     $assert_session->buttonExists('field_twin_media_settings_edit')->press();
     $this->assertElementExistsAfterWait('css', '#field-twin-media .tabledrag-toggle-weight')->press();
diff --git a/core/modules/media_library/tests/src/FunctionalJavascript/WidgetAccessTest.php b/core/modules/media_library/tests/src/FunctionalJavascript/WidgetAccessTest.php
index 0f10d0aa8b..4f0d7bd765 100644
--- a/core/modules/media_library/tests/src/FunctionalJavascript/WidgetAccessTest.php
+++ b/core/modules/media_library/tests/src/FunctionalJavascript/WidgetAccessTest.php
@@ -59,7 +59,7 @@ public function testWidgetAccess() {
     $role->save();
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     // Create a working state.
     $allowed_types = ['type_one', 'type_two', 'type_three', 'type_four'];
@@ -128,9 +128,6 @@ public function testWidgetAccess() {
     $this->drupalGet('media-library', [
       'query' => array_merge($url_options['query'], ['media_library_selected_type' => 'type_one']),
     ]);
-    $this->drupalGet('media-library', [
-      'query' => array_merge($url_options['query'], ['media_library_form_mode' => '   ']),
-    ]);
     $assert_session->responseContains('Access denied');
     $this->drupalGet('media-library', [
       'query' => array_merge($url_options['query'], ['media_library_remaining' => 3]),
diff --git a/core/modules/media_library/tests/src/Kernel/MediaLibraryAccessTest.php b/core/modules/media_library/tests/src/Kernel/MediaLibraryAccessTest.php
index 9ac79c2c14..0046f270ac 100644
--- a/core/modules/media_library/tests/src/Kernel/MediaLibraryAccessTest.php
+++ b/core/modules/media_library/tests/src/Kernel/MediaLibraryAccessTest.php
@@ -109,7 +109,7 @@ public function testFieldWidgetEntityCreateAccess() {
     $ui_builder = $this->container->get('media_library.ui_builder');
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     // Create a media library state to test access.
     $state = MediaLibraryState::create('media_library.opener.field_widget', [
@@ -165,7 +165,7 @@ public function testEditorOpenerAccess($media_embed_enabled, $can_use_format) {
     }
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     $state = MediaLibraryState::create(
       'media_library.opener.editor',
@@ -224,7 +224,7 @@ public function testFieldWidgetEntityEditAccess() {
     $forbidden_entity->save();
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     // Create a media library state to test access.
     $state = MediaLibraryState::create(
@@ -324,7 +324,7 @@ public function testFieldWidgetEntityFieldAccess(string $field_type) {
     $account = $this->createUser(['administer entity_test content']);
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     // Test that access is denied even without an entity to work with.
     $state = MediaLibraryState::create(
@@ -371,7 +371,7 @@ public function testViewAccess() {
     $ui_builder = $this->container->get('media_library.ui_builder');
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     // Create a media library state to test access.
     $state = MediaLibraryState::create(
@@ -442,7 +442,7 @@ public function testAddFormAccess(): void {
     ];
 
     // @todo where should this be pulled from? The field widget specifies.
-    $form_mode = 'media_library';
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
 
     $account = $this->createUser(['create media']);
     $this->setCurrentUser($account);
diff --git a/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php b/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
index b5a2734ad4..d77510705e 100644
--- a/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
+++ b/core/modules/media_library/tests/src/Kernel/MediaLibraryAddFormTest.php
@@ -35,13 +35,6 @@ class MediaLibraryAddFormTest extends KernelTestBase {
     'user',
   ];
 
-  /**
-   * The machine name of the form mode to render the Add media forms.
-   *
-   * Normally specified using the media library Form widget.
-   */
-  protected $form_mode = 'media_library';
-
   /**
    * {@inheritdoc}
    */
@@ -119,7 +112,10 @@ public function testMediaTypeAddForm() {
    *   The render array for the media library.
    */
   protected function buildLibraryUi($selected_type_id) {
-    $state = MediaLibraryState::create('test', ['image', 'remote_video'], $selected_type_id, -1, [], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state = MediaLibraryState::create('test', ['image', 'remote_video'], $selected_type_id, -1, [], $form_mode);
     return \Drupal::service('media_library.ui_builder')->buildUi($state);
   }
 
@@ -137,7 +133,10 @@ public function testFormStateValidation() {
    * Tests the validation of the selected type in the media library add form.
    */
   public function testSelectedTypeValidation() {
-    $state = MediaLibraryState::create('test', ['image', 'remote_video', 'header_image'], 'header_image', -1, [], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state = MediaLibraryState::create('test', ['image', 'remote_video', 'header_image'], 'header_image', -1, [], $form_mode);
     $form_state = new FormState();
     $form_state->set('media_library_state', $state);
     $this->expectException(\InvalidArgumentException::class);
diff --git a/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php b/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
index bce48dbea2..af0003f3b2 100644
--- a/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
+++ b/core/modules/media_library/tests/src/Kernel/MediaLibraryStateTest.php
@@ -76,14 +76,17 @@ public function testMethods() {
     $selected_media_type_id = 'image';
     $remaining_slots = 2;
 
-    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_media_type_id, $remaining_slots, [], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_media_type_id, $remaining_slots, [], $form_mode);
     $this->assertSame($opener_id, $state->getOpenerId());
     $this->assertSame($allowed_media_type_ids, $state->getAllowedTypeIds());
     $this->assertSame($selected_media_type_id, $state->getSelectedTypeId());
     $this->assertSame($remaining_slots, $state->getAvailableSlots());
     $this->assertTrue($state->hasSlotsAvailable());
 
-    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_media_type_id, 0, [], $this->form_mode);
+    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_media_type_id, 0, [], $form_mode);
     $this->assertFalse($state->hasSlotsAvailable());
   }
 
@@ -110,7 +113,10 @@ public function testCreate($opener_id, array $allowed_media_type_ids, $selected_
       $this->expectException(\InvalidArgumentException::class);
       $this->expectExceptionMessage($exception_message);
     }
-    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_type_id, $remaining_slots, [], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state = MediaLibraryState::create($opener_id, $allowed_media_type_ids, $selected_type_id, $remaining_slots, [], $form_mode);
     $this->assertInstanceOf(MediaLibraryState::class, $state);
 
     // Ensure that the state object carries cache metadata.
@@ -284,9 +290,12 @@ public function providerCreate() {
    * @dataProvider providerFromRequest
    */
   public function testFromRequest(array $query_overrides, $exception_expected) {
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
     // Override the query parameters and verify an exception is thrown when
     // required state parameters are changed.
-    $query = MediaLibraryState::create('test', ['file', 'image'], 'image', 2, [], $this->form_mode)->all();
+    $query = MediaLibraryState::create('test', ['file', 'image'], 'image', 2, [], $form_mode)->all();
     $query = array_merge($query, $query_overrides);
     if ($exception_expected) {
       $this->expectException(BadRequestHttpException::class);
@@ -334,7 +343,7 @@ public function providerFromRequest() {
         'media_library_opener_id' => 'test',
         'media_library_allowed_types' => ['file', 'image'],
         'media_library_selected_type' => 'image',
-        'media_library_form_mode' => 'media_library',
+        'media_library_form_mode' => MediaLibraryState::DEFAULT_FORM_MODE,
         'media_library_remaining' => 2,
       ],
       FALSE,
@@ -378,7 +387,10 @@ public function providerFromRequest() {
    * @covers ::getOpenerParameters
    */
   public function testOpenerParameters() {
-    $state = MediaLibraryState::create('test', ['file'], 'file', -1, ['foo' => 'baz'], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state = MediaLibraryState::create('test', ['file'], 'file', -1, ['foo' => 'baz'], $form_mode);
     $this->assertSame(['foo' => 'baz'], $state->getOpenerParameters());
   }
 
@@ -386,8 +398,11 @@ public function testOpenerParameters() {
    * Tests that hash is unaffected by allowed media type order.
    */
   public function testHashUnaffectedByMediaTypeOrder() {
-    $state1 = MediaLibraryState::create('test', ['file', 'image'], 'image', 2, [], $this->form_mode);
-    $state2 = MediaLibraryState::create('test', ['image', 'file'], 'image', 2, [], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state1 = MediaLibraryState::create('test', ['file', 'image'], 'image', 2, [], $form_mode);
+    $state2 = MediaLibraryState::create('test', ['image', 'file'], 'image', 2, [], $form_mode);
     $this->assertSame($state1->getHash(), $state2->getHash());
   }
 
@@ -395,8 +410,11 @@ public function testHashUnaffectedByMediaTypeOrder() {
    * Tests that hash is unaffected by opener parameter order.
    */
   public function testHashUnaffectedByOpenerParamOrder() {
-    $state1 = MediaLibraryState::create('test', ['file'], 'file', -1, ['foo' => 'baz', 'baz' => 'foo'], $this->form_mode);
-    $state2 = MediaLibraryState::create('test', ['file'], 'file', -1, ['baz' => 'foo', 'foo' => 'baz'], $this->form_mode);
+    // @todo where should this be pulled from? The field widget specifies.
+    $form_mode = MediaLibraryState::DEFAULT_FORM_MODE;
+
+    $state1 = MediaLibraryState::create('test', ['file'], 'file', -1, ['foo' => 'baz', 'baz' => 'foo'], $form_mode);
+    $state2 = MediaLibraryState::create('test', ['file'], 'file', -1, ['baz' => 'foo', 'foo' => 'baz'], $form_mode);
     $this->assertSame($state1->getHash(), $state2->getHash());
   }