diff --git a/core/modules/block/block.links.action.yml b/core/modules/block/block.links.action.yml
deleted file mode 100644
index 2340747..0000000
--- a/core/modules/block/block.links.action.yml
+++ /dev/null
@@ -1,10 +0,0 @@
-block_layout_add_action:
-  route_name: block.admin_library
-  title: 'Add block to layout'
-  appears_on:
-    - block.admin_display
-block_layout_add_action_for_theme:
-  route_name: block.admin_library_theme
-  title: 'Add block to layout'
-  appears_on:
-    - block.admin_display_theme
diff --git a/core/modules/block/block.links.task.yml b/core/modules/block/block.links.task.yml
index 123dd4c..bc72260 100644
--- a/core/modules/block/block.links.task.yml
+++ b/core/modules/block/block.links.task.yml
@@ -13,12 +13,3 @@ block.admin_display_theme:
   route_name: block.admin_display_theme
   parent_id: block.admin_display
   deriver: 'Drupal\block\Plugin\Derivative\ThemeLocalTask'
-
-# Per theme block placement pages.
-block.admin_library:
-  route_name: block.admin_library
-  base_route: block.admin_library
-block.admin_library_theme:
-  route_name: block.admin_library_theme
-  parent_id: block.admin_library
-  deriver: 'Drupal\block\Plugin\Derivative\ThemeLocalTask'
diff --git a/core/modules/block/block.module b/core/modules/block/block.module
index a17c89e..9ce0ac2 100644
--- a/core/modules/block/block.module
+++ b/core/modules/block/block.module
@@ -27,7 +27,7 @@ function block_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
       $output .= '<dt>' . t('Placing and moving blocks') . '</dt>';
-      $output .= '<dd>' . t('You can place a new block by clicking on the <em>Add block to layout</em> button on the <a href="!blocks">Block layout page</a> and then choosing a region to place it in. Once a block is placed, it can be moved to a different region by dragging or using the drop-down <em>Region</em> list, and then clicking <em>Save blocks</em>.', array('!blocks' => \Drupal::url('block.admin_display'))) . '</dd>';
+      $output .= '<dd>' . t('You can place a new block by clicking on its title in the <em>Place blocks</em> list on the <a href="!blocks">Block layout page</a> and choosing a region to place it in. Once a block is placed, it can be moved to a different region by dragging or using the drop-down <em>Region</em> list, and then clicking <em>Save blocks</em>.', array('!blocks' => \Drupal::url('block.admin_display'))) . '</dd>';
       $output .= '<dt>' . t('Toggling between different themes') . '</dt>';
       $output .= '<dd>' . t('Blocks are placed and configured specifically for each theme. The Block layout page opens with the default theme, but you can toggle to other installed themes.') . '</dd>';
       $output .= '<dt>' . t('Demonstrating block regions for a theme') . '</dt>';
@@ -37,14 +37,14 @@ function block_help($route_name, RouteMatchInterface $route_match) {
       $output .= '<dt>' . t('Controlling visibility') . '</dt>';
       $output .= '<dd>' . t('You can control the visibility of a block by restricting it to specific pages, content types, and/or roles by setting the appropriate options under <em>Visibility settings</em> of the block configuration.') . '</dd>';
       $output .= '<dt>' . t('Adding custom blocks') . '</dt>';
-      $output .= '<dd>' . t('If the <em>Custom Block</em> module is installed, you can create and add your own blocks using fields and customizable display settings. For more information, see the <a href="!blockcontent-help">Custom Block help page</a>.', array('!blockcontent-help' => $block_content)) . '</dd>';
+      $output .= '<dd>' . t('You can add custom blocks, if the <em>Custom Block</em> module is installed. For more information, see the <a href="!blockcontent-help">Custom Block help page</a>.', array('!blockcontent-help' => $block_content)) . '</dd>';
       $output .= '</dl>';
       return $output;
   }
   if ($route_name == 'block.admin_display' || $route_name == 'block.admin_display_theme') {
     $demo_theme = $route_match->getParameter('theme') ?: \Drupal::config('system.theme')->get('default');
     $themes = \Drupal::service('theme_handler')->listInfo();
-    $output = '<p>' . t('This page provides a drag-and-drop interface for adding a block to a region, and for controlling the order of blocks within regions. Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. To add a block to this theme\'s layout, click the <em>Add block to layout</em> button. After moving blocks, remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page.') . '</p>';
+    $output = '<p>' . t('This page provides a drag-and-drop interface for adding a block to a region, and for controlling the order of blocks within regions. To add a block to a region, or to configure its specific title and visibility settings, click the block title under <em>Place blocks</em>. Since not all themes implement the same regions, or display regions in the same way, blocks are positioned on a per-theme basis. Remember that your changes will not be saved until you click the <em>Save blocks</em> button at the bottom of the page.') . '</p>';
     $output .= '<p>' . \Drupal::l(t('Demonstrate block regions (@theme)', array('@theme' => $themes[$demo_theme]->info['name'])), new Url('block.admin_demo', array('theme' => $demo_theme))) . '</p>';
     return $output;
   }
diff --git a/core/modules/block/block.routing.yml b/core/modules/block/block.routing.yml
index 0ccab2b..396bf0d 100644
--- a/core/modules/block/block.routing.yml
+++ b/core/modules/block/block.routing.yml
@@ -43,18 +43,10 @@ block.admin_display_theme:
     _permission: 'administer blocks'
 
 block.admin_library:
-  path: 'admin/structure/block/library'
-  defaults:
-    _controller: '\Drupal\block\Controller\BlockLibraryController::listBlocks'
-    _title: 'Add block to layout'
-  requirements:
-    _permission: 'administer blocks'
-
-block.admin_library_theme:
   path: 'admin/structure/block/library/{theme}'
   defaults:
     _controller: '\Drupal\block\Controller\BlockLibraryController::listBlocks'
-    _title: 'Add block to layout'
+    _title: 'Place block'
   requirements:
     _access_theme: 'TRUE'
     _permission: 'administer blocks'
diff --git a/core/modules/block/css/block.admin.css b/core/modules/block/css/block.admin.css
index de71682..2b9eb45 100644
--- a/core/modules/block/css/block.admin.css
+++ b/core/modules/block/css/block.admin.css
@@ -1,3 +1,12 @@
+/* Block listing page */
+.region-title .button {
+  margin-left: 1em; /* LTR */
+}
+[dir="rtl"] .region-title .button {
+  margin-left: 0;
+  margin-right: 1em;
+}
+
 /* Block demo mode */
 .block-region {
   background-color: #ff6;
@@ -22,6 +31,7 @@ a.block-demo-backlink:visited {
 a.block-demo-backlink:hover {
   text-decoration: underline;
 }
+
 /* Configure block form - Block description */
 .block-form .form-item-settings-admin-label label {
   display: inline;
diff --git a/core/modules/block/src/BlockForm.php b/core/modules/block/src/BlockForm.php
index eac4d51..8c13bbb 100644
--- a/core/modules/block/src/BlockForm.php
+++ b/core/modules/block/src/BlockForm.php
@@ -170,11 +170,13 @@ public function form(array $form, FormStateInterface $form_state) {
     }
 
     // Region settings.
+    $entity_region = $entity->getRegion();
+    $region = $entity->isNew() ? $this->getRequest()->query->get('region', $entity_region) : $entity_region;
     $form['region'] = array(
       '#type' => 'select',
       '#title' => $this->t('Region'),
       '#description' => $this->t('Select the region where this block should be displayed.'),
-      '#default_value' => $entity->getRegion(),
+      '#default_value' => $region,
       '#empty_value' => BlockInterface::BLOCK_REGION_NONE,
       '#options' => system_region_list($theme, REGIONS_VISIBLE),
       '#prefix' => '<div id="edit-block-region-wrapper">',
diff --git a/core/modules/block/src/BlockListBuilder.php b/core/modules/block/src/BlockListBuilder.php
index 52f4e99..6288824 100644
--- a/core/modules/block/src/BlockListBuilder.php
+++ b/core/modules/block/src/BlockListBuilder.php
@@ -8,6 +8,7 @@
 namespace Drupal\block;
 
 use Drupal\Component\Utility\Html;
+use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Config\Entity\ConfigEntityListBuilder;
 use Drupal\Core\Entity\EntityInterface;
@@ -17,6 +18,7 @@
 use Drupal\Core\Form\FormInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Theme\ThemeManagerInterface;
+use Drupal\Core\Url;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -213,10 +215,20 @@ protected function buildBlocksForm() {
         ),
       );
       $form['region-' . $region]['title'] = array(
-        '#markup' => $region != BlockInterface::BLOCK_REGION_NONE ? $title : $this->t('Disabled', array(), array('context' => 'Plural')),
+        '#prefix' => $region != BlockInterface::BLOCK_REGION_NONE ? $title : $this->t('Disabled', array(), array('context' => 'Plural')),
+        '#type' => 'link',
+        '#title' => $this->t('Place block'),
+        '#url' => Url::fromRoute('block.admin_library', ['theme' => $this->getThemeName()], ['query' => ['region' => $region]]),
         '#wrapper_attributes' => array(
           'colspan' => 5,
         ),
+        '#attributes' => [
+          'class' => ['use-ajax', 'button', 'button--small'],
+          'data-dialog-type' => 'modal',
+          'data-dialog-options' => Json::encode([
+            'width' => 700,
+          ]),
+        ],
       );
 
       $form['region-' . $region . '-message'] = array(
diff --git a/core/modules/block/src/Controller/BlockLibraryController.php b/core/modules/block/src/Controller/BlockLibraryController.php
index 703089c..b2a6602 100644
--- a/core/modules/block/src/Controller/BlockLibraryController.php
+++ b/core/modules/block/src/Controller/BlockLibraryController.php
@@ -7,11 +7,13 @@
 
 namespace Drupal\block\Controller;
 
+use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Block\BlockManagerInterface;
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\Core\Url;
 use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Provides a list of block plugins to be added to the layout.
@@ -53,9 +55,7 @@ public static function create(ContainerInterface $container) {
    * @return array
    *   A render array as expected by the renderer.
    */
-  public function listBlocks($theme = NULL) {
-    $theme = $theme ?: $this->config('system.theme')->get('default');
-
+  public function listBlocks(Request $request ,$theme) {
     $headers = [
       ['data' => $this->t('Block')],
       ['data' => $this->t('Category')],
@@ -67,6 +67,7 @@ public function listBlocks($theme = NULL) {
     // Order by category, and then by admin label.
     $definitions = $this->blockManager->getSortedDefinitions($definitions);
 
+    $region = $request->query->get('region');
     $rows = array();
     foreach ($definitions as $plugin_id => $plugin_definition) {
       $row = [];
@@ -77,9 +78,19 @@ public function listBlocks($theme = NULL) {
       ];
       $row['category']['data'] = SafeMarkup::checkPlain($plugin_definition['category']);
       $links['add'] = [
-        'title' => $this->t('Add block'),
+        'title' => $this->t('Place block'),
         'url' => Url::fromRoute('block.admin_add', ['plugin_id' => $plugin_id, 'theme' => $theme]),
+        'attributes' => array(
+          'class' => array('use-ajax'),
+          'data-dialog-type' => 'modal',
+          'data-dialog-options' => Json::encode([
+            'width' => 700,
+          ]),
+        ),
       ];
+      if ($region) {
+        $links['add']['query']['region'] = $region;
+      }
       $row['operations']['data'] = [
         '#type' => 'operations',
         '#links' => $links,
diff --git a/core/modules/block/src/Tests/BlockLanguageCacheTest.php b/core/modules/block/src/Tests/BlockLanguageCacheTest.php
index c07731d..543e65e 100644
--- a/core/modules/block/src/Tests/BlockLanguageCacheTest.php
+++ b/core/modules/block/src/Tests/BlockLanguageCacheTest.php
@@ -8,7 +8,6 @@
 namespace Drupal\block\Tests;
 
 use Drupal\Component\Utility\Unicode;
-use Drupal\Core\Url;
 use Drupal\language\Entity\ConfigurableLanguage;
 use Drupal\simpletest\WebTestBase;
 
@@ -60,10 +59,10 @@ public function testBlockLinks() {
     ));
     $this->drupalLogin($admin_user);
 
-    $url = Url::fromRoute('block.admin_library');
     // Create the block cache for all languages.
     foreach ($this->langcodes as $langcode) {
-      $this->drupalGet($url, array('language' => $langcode));
+      $this->drupalGet('admin/structure/block', array('language' => $langcode));
+      $this->clickLink('Place block');
     }
 
     // Create a menu in the default language.
@@ -74,7 +73,8 @@ public function testBlockLinks() {
 
     // Check that the block is listed for all languages.
     foreach ($this->langcodes as $langcode) {
-      $this->drupalGet($url, array('language' => $langcode));
+      $this->drupalGet('admin/structure/block', array('language' => $langcode));
+      $this->clickLink('Place block');
       $this->assertText($edit['label']);
     }
   }
diff --git a/core/modules/block/src/Tests/BlockUiTest.php b/core/modules/block/src/Tests/BlockUiTest.php
index 28426f6..1f26739 100644
--- a/core/modules/block/src/Tests/BlockUiTest.php
+++ b/core/modules/block/src/Tests/BlockUiTest.php
@@ -8,7 +8,6 @@
 namespace Drupal\block\Tests;
 
 use Drupal\Component\Utility\Html;
-use Drupal\Core\Url;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -146,8 +145,8 @@ public function testCandidateBlockList() {
     );
     $pattern = '//tr[.//td/div[text()=:title] and .//td[text()=:category] and .//td//a[contains(@href, :href)]]';
 
-    // Check if the block is listed.
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet('admin/structure/block');
+    $this->clickLink('Place block');
     $elements = $this->xpath($pattern, $arguments);
     $this->assertTrue(!empty($elements), 'The test block appears in the category for its module.');
 
@@ -155,9 +154,9 @@ public function testCandidateBlockList() {
     $this->container->get('state')->set('block_test_info_alter', TRUE);
     $this->container->get('plugin.manager.block')->clearCachedDefinitions();
 
-    // Check if the block is listed with a custom category.
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
-    $arguments[':category'] = "Custom category";
+    $this->drupalGet('admin/structure/block');
+    $this->clickLink('Place block');
+    $arguments[':category'] = 'Custom category';
     $elements = $this->xpath($pattern, $arguments);
     $this->assertTrue(!empty($elements), 'The test block appears in a custom category controlled by block_test_block_alter().');
   }
diff --git a/core/modules/block/src/Tests/BlockXssTest.php b/core/modules/block/src/Tests/BlockXssTest.php
index 97a4559..5cd6477 100644
--- a/core/modules/block/src/Tests/BlockXssTest.php
+++ b/core/modules/block/src/Tests/BlockXssTest.php
@@ -31,7 +31,7 @@ class BlockXssTest extends WebTestBase {
   /**
    * Test XSS in title.
    */
-  public function testXSSInTitle() {
+  public function testXssInTitle() {
     $this->drupalPlaceBlock('test_xss_title', array('label' => '<script>alert("XSS label");</script>'));
 
     \Drupal::state()->set('block_test.content', $this->randomMachineName());
@@ -45,12 +45,13 @@ public function testXSSInTitle() {
   }
 
   /**
-   * Test XSS in title.
+   * Tests XSS in category.
    */
-  public function testXSSInCategory() {
+  public function testXssInCategory() {
     $this->drupalPlaceBlock('test_xss_title');
     $this->drupalLogin($this->drupalCreateUser(['administer blocks', 'access administration pages']));
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet(Url::fromRoute('block.admin_display'));
+    $this->clickLink('Place block');
     $this->assertNoRaw("<script>alert('XSS category');</script>");
   }
 
@@ -76,7 +77,8 @@ protected function doViewTest() {
     $view->addDisplay('block');
     $view->save();
 
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet(Url::fromRoute('block.admin_display'));
+    $this->clickLink('Place block');
     // The block admin label is automatically XSS admin filtered.
     $this->assertRaw('alert("view");');
     $this->assertNoRaw('<script>alert("view");</script>');
@@ -91,7 +93,8 @@ protected function doMenuTest() {
       'label' => '<script>alert("menu");</script>',
     ])->save();
 
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet(Url::fromRoute('block.admin_display'));
+    $this->clickLink('Place block');
     // The block admin label is automatically XSS admin filtered.
     $this->assertRaw('alert("menu");');
     $this->assertNoRaw('<script>alert("menu");</script>');
@@ -111,7 +114,8 @@ protected function doBlockContentTest() {
       'info' => '<script>alert("block_content");</script>',
     ])->save();
 
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet(Url::fromRoute('block.admin_display'));
+    $this->clickLink('Place block');
     // The block admin label is automatically XSS admin filtered.
     $this->assertRaw('alert("block_content");');
     $this->assertNoRaw('<script>alert("block_content");</script>');
diff --git a/core/modules/block/src/Tests/Views/DisplayBlockTest.php b/core/modules/block/src/Tests/Views/DisplayBlockTest.php
index 24dc5c1..d9f9196 100644
--- a/core/modules/block/src/Tests/Views/DisplayBlockTest.php
+++ b/core/modules/block/src/Tests/Views/DisplayBlockTest.php
@@ -8,7 +8,6 @@
 namespace Drupal\block\Tests\Views;
 
 use Drupal\Component\Serialization\Json;
-use Drupal\Core\Url;
 use Drupal\views\Views;
 use Drupal\views\Tests\ViewTestBase;
 use Drupal\views\Tests\ViewTestData;
@@ -70,7 +69,8 @@ public function testBlockCategory() {
       )),
       ':category' => t('Lists (Views)'),
     );
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet('admin/structure/block');
+    $this->clickLink('Place block');
     $elements = $this->xpath($pattern, $arguments);
     $this->assertTrue(!empty($elements), 'The test block appears in the category for its base table.');
 
@@ -94,7 +94,8 @@ public function testBlockCategory() {
 
     // Test that the blocks are listed under the correct categories.
     $arguments[':category'] = $category;
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet('admin/structure/block');
+    $this->clickLink('Place block');
     $elements = $this->xpath($pattern, $arguments);
     $this->assertTrue(!empty($elements), 'The test block appears in the custom category.');
 
diff --git a/core/modules/block/templates/block-list.html.twig b/core/modules/block/templates/block-list.html.twig
new file mode 100644
index 0000000..854d3ce
--- /dev/null
+++ b/core/modules/block/templates/block-list.html.twig
@@ -0,0 +1,23 @@
+{#
+/**
+ * @file
+ * Two column template for the block add/edit form.
+ *
+ * This template will be used when a block edit form specifies 'block_edit_form'
+ * as its #theme callback.  Otherwise, by default, block add/edit forms will be
+ * themed by form.html.twig.
+ *
+ * Available variables:
+ * - form: The block add/edit form.
+ *
+ * @ingroup themeable
+ */
+#}
+<div class="layout-block-list clearfix">
+  <div class="layout-region block-list-primary">
+    {{ form|without('place_blocks') }}
+  </div>
+  <div class="layout-region block-list-secondary">
+    {{ form.place_blocks }}
+  </div>
+</div>
diff --git a/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestXSSTitleBlock.php b/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestXSSTitleBlock.php
index 1f028c3..3146b59 100644
--- a/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestXSSTitleBlock.php
+++ b/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestXSSTitleBlock.php
@@ -8,11 +8,10 @@
 namespace Drupal\block_test\Plugin\Block;
 
 /**
- * Provides a block to test XSS in the title and category.
+ * Provides a block to test XSS in title.
  *
  * @Block(
  *   id = "test_xss_title",
- *   category = @Translation("<script>alert('XSS category');</script>"),
  *   admin_label = "<script>alert('XSS subject');</script>"
  * )
  */
diff --git a/core/modules/block_content/block_content.links.action.yml b/core/modules/block_content/block_content.links.action.yml
index b55361a..4772a6f 100644
--- a/core/modules/block_content/block_content.links.action.yml
+++ b/core/modules/block_content/block_content.links.action.yml
@@ -8,5 +8,6 @@ block_content_add_action:
   route_name: block_content.add_page
   title: 'Add custom block'
   appears_on:
+    - block.admin_library
     - entity.block_content.collection
   class: \Drupal\block_content\Plugin\Menu\LocalAction\BlockContentAddLocalAction
diff --git a/core/modules/block_content/block_content.links.task.yml b/core/modules/block_content/block_content.links.task.yml
index e6b0545..2b88171 100644
--- a/core/modules/block_content/block_content.links.task.yml
+++ b/core/modules/block_content/block_content.links.task.yml
@@ -1,5 +1,5 @@
 entity.block_content.collection:
-  title: 'Custom blocks'
+  title: 'Custom block library'
   route_name: entity.block_content.collection
   base_route: block.admin_display
 block_content.list_sub:
diff --git a/core/modules/block_content/block_content.module b/core/modules/block_content/block_content.module
index bc00d7a..04a1e6c 100644
--- a/core/modules/block_content/block_content.module
+++ b/core/modules/block_content/block_content.module
@@ -18,23 +18,24 @@ function block_content_help($route_name, RouteMatchInterface $route_match) {
       $field_ui = \Drupal::moduleHandler()->moduleExists('field_ui') ? \Drupal::url('help.page', array('name' => 'field_ui')) : '#';
       $output = '';
       $output .= '<h3>' . t('About') . '</h3>';
-      $output .= '<p>' . t('The Custom Block module allows you to create custom <em>block types</em> and <em>content-containing blocks</em> based on those types. A list of all custom blocks is available at the <a href="!block-listing">Custom blocks</a> page. Custom block types have fields; see the <a href="!field-help">Field module help</a> for more information. Once created, custom blocks can be placed in regions just like blocks provided by other modules; see the <a href="!blocks">Block module help page</a> for details. For more information, see <a href="!online-help">the online documentation for the Custom Block module</a>.', array('!block-listing' => \Drupal::url('entity.block_content.collection'), '!block-content' => \Drupal::url('entity.block_content.collection'), '!field-help' => \Drupal::url('help.page', array('name' => 'field')), '!blocks' => \Drupal::url('help.page', array('name' => 'block')), '!online-help' => 'https://www.drupal.org/documentation/modules/block_content')) . '</p>';
+      $output .= '<p>' . t('The Custom Block module allows you to create custom <em>block types</em> and <em>content-containing blocks</em>, and provides a <a href="!block-library">Custom block library</a> listing all of them. Custom block types have fields; see the <a href="!field-help">Field module help</a> for more information. Once created, custom blocks can be placed in regions just like blocks provided by other modules; see the <a href="!blocks">Block module help page</a> for details. For more information, see <a href="!online-help">the online documentation for the Custom Block module</a>.', array('!block-library' => \Drupal::url('entity.block_content.collection'), '!block-content' => \Drupal::url('entity.block_content.collection'), '!field-help' => \Drupal::url('help.page', array('name' => 'field')), '!blocks' => \Drupal::url('help.page', array('name' => 'block')), '!online-help' => 'https://www.drupal.org/documentation/modules/block_content')) . '</p>';
       $output .= '<h3>' . t('Uses') . '</h3>';
       $output .= '<dl>';
       $output .= '<dt>' . t('Creating and managing custom block types') . '</dt>';
-      $output .= '<dd>' . t('Users with the <em>Administer blocks</em> permission can create custom block types using fields and manage existing block types, from the <a href="!types">Custom block types</a> page. For more information about managing fields and display settings, see the <a href="!field-ui">Field UI module help</a>.', array('!types' => \Drupal::url('entity.block_content_type.collection'), '!field-ui' => $field_ui)) . '</dd>';
+      $output .= '<dd>' . t('Users with the <em>Administer blocks</em> permission can create and edit custom block types with fields and display settings, from the <a href="!types">Custom block types</a> page in the Custom block library. For more information about managing fields and display settings, see the <a href="!field-ui">Field UI module help</a>.', array('!types' => \Drupal::url('entity.block_content_type.collection'), '!field-ui' => $field_ui)) . '</dd>';
       $output .= '<dt>' . t('Creating custom blocks') . '</dt>';
-      $output .= '<dd>' . t('Users with the <em>Administer blocks</em> permission can create, edit, and delete custom blocks from the <a href="!block-listing">Custom blocks</a> page. Custom blocks can be added to a theme\'s layout on the <a href="!blocks">Block layout page</a>; see the <a href="!block_help">Block module help</a> for more information about placing blocks.', array('!blocks' => \Drupal::url('block.admin_display'), '!block-listing' => \Drupal::url('entity.block_content.collection'), '!block_help' => \Drupal::url('help.page', array('name' => 'block')))) . '</dd>';
+      $output .= '<dd>' . t('Users with the <em>Administer blocks</em> permission can create, edit, and delete custom blocks of each custom block type you have defined, from the <a href="!block-library">Custom block library</a> page. Custom blocks are shown in the <em>Place blocks</em> list on the <a href="!blocks">Block layout page</a>; see the <a href="!block_help">Block module help</a> for more information about placing blocks.', array('!blocks' => \Drupal::url('block.admin_display'), '!block-library' => \Drupal::url('entity.block_content.collection'), '!block_help' => \Drupal::url('help.page', array('name' => 'block')))) . '</dd>';
       $output .= '</dl>';
       return $output;
 
     case 'entity.block_content.collection':
-      $output = '<p>' . t('Every custom block is based on a <a href="!types">block type</a>, each with its own fields and display settings. After creating a block, place it in a region from the <a href="!blocks">Block layout page</a>.', array('!types' => \Drupal::url('entity.block_content_type.collection'), '!blocks' => \Drupal::url('block.admin_display'))) . '</p>';
+      $output = '<p>' . t('Blocks in the block library belong to <a href="!types">block types</a>, each with its own fields and display settings. After creating a block, place it in a region from the <a href="!blocks">Block layout page</a>.', array('!types' => \Drupal::url('entity.block_content_type.collection'), '!blocks' => \Drupal::url('block.admin_display'))) . '</p>';
       return $output;
 
     case 'entity.block_content_type.collection':
-      $output = '<p>' . t('After creating a type, you can then create a block based on it from the <a href="!block-listing">custom blocks page</a>.', array('!block-listing' => \Drupal::url('entity.block_content.collection'))) . '</p>';
+      $output = '<p>' . t('Each block type has its own fields and display settings. Create blocks of each type on the <a href="!block-library">Block library page</a>.', array('!block-library' => \Drupal::url('entity.block_content.collection'))) . '</p>';
       return $output;
+
   }
 }
 
diff --git a/core/modules/block_content/block_content.routing.yml b/core/modules/block_content/block_content.routing.yml
index fc48fb1..3542ca8 100644
--- a/core/modules/block_content/block_content.routing.yml
+++ b/core/modules/block_content/block_content.routing.yml
@@ -2,7 +2,7 @@ entity.block_content_type.collection:
   path: '/admin/structure/block/block-content/types'
   defaults:
     _entity_list: 'block_content_type'
-    _title: 'Custom blocks'
+    _title: 'Custom block library'
   requirements:
     _permission: 'administer blocks'
 
@@ -83,7 +83,7 @@ entity.block_content_type.edit_form:
 entity.block_content.collection:
   path: '/admin/structure/block/block-content'
   defaults:
-    _title: 'Custom blocks'
+    _title: 'Custom block library'
     _entity_list: 'block_content'
   requirements:
     _permission: 'administer blocks'
diff --git a/core/modules/block_content/config/optional/views.view.block_content.yml b/core/modules/block_content/config/optional/views.view.block_content.yml
index 8efe9df..ad5e1f9 100644
--- a/core/modules/block_content/config/optional/views.view.block_content.yml
+++ b/core/modules/block_content/config/optional/views.view.block_content.yml
@@ -5,7 +5,7 @@ dependencies:
     - block_content
     - user
 id: block_content
-label: 'Custom blocks'
+label: 'Custom block library'
 module: views
 description: 'Find and manage custom blocks.'
 tag: ''
@@ -430,7 +430,7 @@ display:
           entity_field: type
           plugin_id: bundle
       sorts: {  }
-      title: 'Custom blocks'
+      title: 'Custom block library'
       header: {  }
       footer: {  }
       empty:
@@ -475,7 +475,7 @@ display:
       path: admin/structure/block/block-content
       menu:
         type: tab
-        title: 'Custom blocks'
+        title: 'Custom block library'
         description: ''
         parent: block.admin_display
         weight: 0
diff --git a/core/modules/block_content/src/BlockContentInterface.php b/core/modules/block_content/src/BlockContentInterface.php
index 47c9c93..50f4d35 100644
--- a/core/modules/block_content/src/BlockContentInterface.php
+++ b/core/modules/block_content/src/BlockContentInterface.php
@@ -48,7 +48,7 @@ public function setRevisionLog($revision_log);
   /**
    * Sets the theme value.
    *
-   * When creating a new block content block from the block listing, the user is
+   * When creating a new block content block from the block library, the user is
    * redirected to the configure form for that block in the given theme. The
    * theme is stored against the block when the block content add form is shown.
    *
@@ -63,7 +63,7 @@ public function setTheme($theme);
   /**
    * Gets the theme value.
    *
-   * When creating a new block content block from the block listing, the user is
+   * When creating a new block content block from the block library, the user is
    * redirected to the configure form for that block in the given theme. The
    * theme is stored against the block when the block content add form is shown.
    *
diff --git a/core/modules/block_content/src/BlockContentViewsData.php b/core/modules/block_content/src/BlockContentViewsData.php
index 410d4a9..abb2cb2 100644
--- a/core/modules/block_content/src/BlockContentViewsData.php
+++ b/core/modules/block_content/src/BlockContentViewsData.php
@@ -29,7 +29,7 @@ public function getViewsData() {
     $data['block_content_field_data']['type']['field']['id'] = 'field';
 
     $data['block_content']['block_content_listing_empty'] = array(
-      'title' => t('Empty block listing behavior'),
+      'title' => t('Empty block library behavior'),
       'help' => t('Provides a link to add a new block.'),
       'area' => array(
         'id' => 'block_content_listing_empty',
diff --git a/core/modules/block_content/src/Controller/BlockContentController.php b/core/modules/block_content/src/Controller/BlockContentController.php
index 6e3ae86..f712367 100644
--- a/core/modules/block_content/src/Controller/BlockContentController.php
+++ b/core/modules/block_content/src/Controller/BlockContentController.php
@@ -111,9 +111,9 @@ public function addForm(BlockContentTypeInterface $block_content_type, Request $
       'type' => $block_content_type->id()
     ));
     if (($theme = $request->query->get('theme')) && in_array($theme, array_keys($this->themeHandler->listInfo()))) {
-      // We have navigated to this page from the block listing and will keep
-      // track of the theme for redirecting the user to the configuration page
-      // for the newly created block in the given theme.
+      // We have navigated to this page from the block library and will keep track
+      // of the theme for redirecting the user to the configuration page for the
+      // newly created block in the given theme.
       $block->setTheme($theme);
     }
     return $this->entityFormBuilder()->getForm($block);
diff --git a/core/modules/block_content/src/Entity/BlockContent.php b/core/modules/block_content/src/Entity/BlockContent.php
index 359515a..4e186b9 100644
--- a/core/modules/block_content/src/Entity/BlockContent.php
+++ b/core/modules/block_content/src/Entity/BlockContent.php
@@ -71,7 +71,7 @@ class BlockContent extends ContentEntityBase implements BlockContentInterface {
   /**
    * The theme the block is being created in.
    *
-   * When creating a new custom block from the block listing, the user is
+   * When creating a new custom block from the block library, the user is
    * redirected to the configure form for that block in the given theme. The
    * theme is stored against the block when the custom block add form is shown.
    *
diff --git a/core/modules/block_content/src/Tests/BlockContentListTest.php b/core/modules/block_content/src/Tests/BlockContentListTest.php
index 30d1585..aeed4dc 100644
--- a/core/modules/block_content/src/Tests/BlockContentListTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentListTest.php
@@ -33,7 +33,7 @@ public function testListing() {
     $this->drupalGet('admin/structure/block/block-content');
 
     // Test for the page title.
-    $this->assertTitle(t('Custom blocks') . ' | Drupal');
+    $this->assertTitle(t('Custom block library') . ' | Drupal');
 
     // Test for the table.
     $element = $this->xpath('//div[@class="layout-content"]//table');
diff --git a/core/modules/block_content/src/Tests/BlockContentListViewsTest.php b/core/modules/block_content/src/Tests/BlockContentListViewsTest.php
index 6c273c6..ba84f2b 100644
--- a/core/modules/block_content/src/Tests/BlockContentListViewsTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentListViewsTest.php
@@ -31,7 +31,7 @@ public function testListing() {
     $this->drupalGet('admin/structure/block/block-content');
 
     // Test for the page title.
-    $this->assertTitle(t('Custom blocks') . ' | Drupal');
+    $this->assertTitle(t('Custom block library') . ' | Drupal');
 
     // Test for the table.
     $element = $this->xpath('//div[@class="layout-content"]//table');
diff --git a/core/modules/block_content/src/Tests/BlockContentTypeTest.php b/core/modules/block_content/src/Tests/BlockContentTypeTest.php
index 33fcfed..4270538 100644
--- a/core/modules/block_content/src/Tests/BlockContentTypeTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentTypeTest.php
@@ -185,10 +185,20 @@ public function testsBlockContentAddTypes() {
       // For each installed theme, go to its block page and test the redirects.
       $themes = array('bartik', 'classy', 'seven');
       foreach ($themes as $theme) {
-        // Test that adding a block from a 'custom block' link sends you to the
+        // Test that adding a block from the 'place blocks' form sends you to the
         // block configure form.
-        $this->drupalGet('block/add', ['query' => ['theme' => $theme]]);
-        $this->clickLink('foo');
+        $path = $theme == $default_theme ? 'admin/structure/block' : "admin/structure/block/list/$theme";
+        $this->drupalGet($path);
+        $this->clickLink(t('Add custom block'));
+        // The seven theme has markup inside the link, we cannot use clickLink().
+        if ($default_theme == 'seven') {
+          $options = $theme != $default_theme ? array('query' => array('theme' => $theme)) : array();
+          $this->assertLinkByHref(\Drupal::url('block_content.add_form', array('block_content_type' => 'foo'), $options));
+          $this->drupalGet('block/add/foo', $options);
+        }
+        else {
+          $this->clickLink('foo');
+        }
         // Create a new block.
         $edit = array('info[0][value]' => $this->randomMachineName(8));
         $this->drupalPostForm(NULL, $edit, t('Save'));
diff --git a/core/modules/menu_ui/src/Tests/MenuTest.php b/core/modules/menu_ui/src/Tests/MenuTest.php
index e2a85fb..3c00e92 100644
--- a/core/modules/menu_ui/src/Tests/MenuTest.php
+++ b/core/modules/menu_ui/src/Tests/MenuTest.php
@@ -10,6 +10,7 @@
 use Drupal\block\Entity\Block;
 use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Cache\Cache;
 use Drupal\Core\Menu\MenuLinkInterface;
 use Drupal\Core\Url;
 use Drupal\menu_link_content\Entity\MenuLinkContent;
@@ -180,7 +181,7 @@ function addCustomMenuCRUD() {
    * @return \Drupal\system\Entity\Menu
    *   The custom menu that has been created.
    */
-  protected function addCustomMenu() {
+  function addCustomMenu() {
     // Try adding a menu using a menu_name that is too long.
     $this->drupalGet('admin/structure/menu/add');
     $menu_name = substr(hash('sha256', $this->randomMachineName(16)), 0, MENU_MAX_MENU_NAME_LENGTH_UI + 1);
@@ -217,7 +218,8 @@ protected function addCustomMenu() {
     $this->assertText($label, 'Menu created');
 
     // Confirm that the custom menu block is available.
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $this->config('system.theme')->get('default')]));
+    $this->drupalGet('admin/structure/block/list/' . $this->config('system.theme')->get('default'));
+    $this->clickLink('Place block');
     $this->assertText($label);
 
     // Enable the block.
@@ -530,7 +532,8 @@ function testSystemMenuRename() {
 
     // Make sure menu shows up with new name in block addition.
     $default_theme = $this->config('system.theme')->get('default');
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $default_theme]));
+    $this->drupalget('admin/structure/block/list/' . $default_theme);
+    $this->clickLink('Place block');
     $this->assertText($edit['label']);
   }
 
diff --git a/core/modules/search/src/Tests/SearchBlockTest.php b/core/modules/search/src/Tests/SearchBlockTest.php
index e742d91..2348ae0 100644
--- a/core/modules/search/src/Tests/SearchBlockTest.php
+++ b/core/modules/search/src/Tests/SearchBlockTest.php
@@ -6,7 +6,6 @@
  */
 
 namespace Drupal\search\Tests;
-use Drupal\Core\Url;
 
 /**
  * Tests if the search form block is available.
@@ -36,7 +35,8 @@ protected function setUp() {
   public function testSearchFormBlock() {
 
     // Test availability of the search block in the admin "Place blocks" list.
-    $this->drupalGet(Url::fromRoute('block.admin_library'));
+    $this->drupalGet('admin/structure/block');
+    $this->clickLink('Place block');
     $this->assertLinkByHref('/admin/structure/block/add/search_form_block/classy', 0,
       'Did not find the search block in block candidate list.');
 
diff --git a/core/modules/views/src/Tests/Wizard/BasicTest.php b/core/modules/views/src/Tests/Wizard/BasicTest.php
index 88c767b..2ba0dac 100644
--- a/core/modules/views/src/Tests/Wizard/BasicTest.php
+++ b/core/modules/views/src/Tests/Wizard/BasicTest.php
@@ -132,7 +132,8 @@ function testViewsWizardAndListing() {
     $this->assertNoText('REST export', 'If only the page and block options were enabled in the wizard, the resulting view does not have a REST export display.');
 
     // Confirm that the block is available in the block administration UI.
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $this->config('system.theme')->get('default')]));
+    $this->drupalGet('admin/structure/block/list/' . $this->config('system.theme')->get('default'));
+    $this->clickLink('Place block');
     $this->assertText($view3['label']);
 
     // Place the block.
diff --git a/core/modules/views/src/Tests/Wizard/ItemsPerPageTest.php b/core/modules/views/src/Tests/Wizard/ItemsPerPageTest.php
index ea46eb0..7fd06d0 100644
--- a/core/modules/views/src/Tests/Wizard/ItemsPerPageTest.php
+++ b/core/modules/views/src/Tests/Wizard/ItemsPerPageTest.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\views\Tests\Wizard;
 
-use Drupal\Core\Url;
-
 /**
  * Tests the ability of the views wizard to specify the number of items per
  * page.
@@ -72,7 +70,8 @@ function testItemsPerPage() {
     $this->assertTrue($pos5 < $pos4 && $pos4 < $pos3 && $pos3 < $pos2, 'The nodes appear in the expected order in the page display.');
 
     // Confirm that the block is listed in the block administration UI.
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $this->config('system.theme')->get('default')]));
+    $this->drupalGet('admin/structure/block/list/' . $this->config('system.theme')->get('default'));
+    $this->clickLink('Place block');
     $this->assertText($view['label']);
 
     // Place the block, visit a page that displays the block, and check that the
diff --git a/core/modules/views_ui/src/Tests/OverrideDisplaysTest.php b/core/modules/views_ui/src/Tests/OverrideDisplaysTest.php
index 145542a..15b6c88 100644
--- a/core/modules/views_ui/src/Tests/OverrideDisplaysTest.php
+++ b/core/modules/views_ui/src/Tests/OverrideDisplaysTest.php
@@ -7,8 +7,6 @@
 
 namespace Drupal\views_ui\Tests;
 
-use Drupal\Core\Url;
-
 /**
  * Tests that displays can be correctly overridden via the user interface.
  *
@@ -51,7 +49,8 @@ function testOverrideDisplays() {
     $this->assertText($original_title);
 
     // Confirm that the view block is available in the block administration UI.
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $this->config('system.theme')->get('default')]));
+    $this->drupalGet('admin/structure/block/list/' . $this->config('system.theme')->get('default'));
+    $this->clickLink('Place block');
     $this->assertText($view['label']);
 
     // Place the block.
@@ -110,7 +109,8 @@ function testWizardMixedDefaultOverriddenDisplays() {
     $this->assertNoText($view['block[title]']);
 
     // Confirm that the block is available in the block administration UI.
-    $this->drupalGet(Url::fromRoute('block.admin_library_theme', ['theme' => $this->config('system.theme')->get('default')]));
+    $this->drupalGet('admin/structure/block/list/' . $this->config('system.theme')->get('default'));
+    $this->clickLink('Place block');
     $this->assertText($view['label']);
 
     // Put the block into the first sidebar region, and make sure it will not