diff --git a/core/modules/block_content/block_content.install b/core/modules/block_content/block_content.install
index e3da6bde881cddfc1e55d56150c2f6079a2c296f..fab15b4f88c2feb8d297525a5adb6659195ace6c 100644
--- a/core/modules/block_content/block_content.install
+++ b/core/modules/block_content/block_content.install
@@ -138,3 +138,19 @@ function block_content_update_8400() {
     $definition_update_manager->uninstallFieldStorageDefinition($content_translation_status);
   }
 }
+
+/**
+ * Add 'reusable' field to 'block_content' entities.
+ */
+function block_content_update_8600() {
+  $reusable = BaseFieldDefinition::create('boolean')
+    ->setLabel(t('Reusable'))
+    ->setDescription(t('A boolean indicating whether this block is reusable.'))
+    ->setTranslatable(FALSE)
+    ->setRevisionable(FALSE)
+    ->setDefaultValue(TRUE)
+    ->setInitialValue(TRUE);
+
+  \Drupal::entityDefinitionUpdateManager()
+    ->installFieldStorageDefinition('reusable', 'block_content', 'block_content', $reusable);
+}
diff --git a/core/modules/block_content/block_content.module b/core/modules/block_content/block_content.module
index 3adc979d9f08feb3b33d56f85ac87bbd5a46c5fb..98f0925ab96a9643dc3d9dfafc1a90de1e44d4b7 100644
--- a/core/modules/block_content/block_content.module
+++ b/core/modules/block_content/block_content.module
@@ -8,6 +8,9 @@
 use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Core\Database\Query\SelectInterface;
+use Drupal\Core\Database\Query\AlterableInterface;
+use Drupal\Core\Database\Query\ConditionInterface;
 
 /**
  * Implements hook_help().
@@ -105,3 +108,73 @@ function block_content_add_body_field($block_type_id, $label = 'Body') {
 
   return $field;
 }
+
+/**
+ * Implements hook_query_TAG_alter().
+ *
+ * Alters any 'entity_reference' query where the entity type is
+ * 'block_content' and the query has the tag 'block_content_access'.
+ *
+ * These queries should only return reusable blocks unless a condition on
+ * 'reusable' is explicitly set.
+ *
+ * Block_content entities that are reusable should by default not be selectable
+ * as entity reference values. A module can still create an instance of
+ * \Drupal\Core\Entity\EntityReferenceSelection\SelectionInterface
+ * that will allow selection of non-reusable blocks by explicitly setting
+ * a condition on the 'reusable' field.
+ *
+ * @see \Drupal\block_content\BlockContentAccessControlHandler
+ */
+function block_content_query_entity_reference_alter(AlterableInterface $query) {
+  if ($query instanceof SelectInterface && $query->getMetaData('entity_type') === 'block_content' && $query->hasTag('block_content_access')) {
+    $data_table = \Drupal::entityTypeManager()->getDefinition('block_content')->getDataTable();
+    if (array_key_exists($data_table, $query->getTables()) && !_block_content_has_reusable_condition($query->conditions(), $query->getTables())) {
+      $query->condition("$data_table.reusable", TRUE);
+    }
+  }
+}
+
+/**
+ * Utility function to find nested conditions using the reusable field.
+ *
+ * @todo Replace this function with a call to the API in
+ *   https://www.drupal.org/project/drupal/issues/2984930
+ *
+ * @param array $condition
+ *   The condition or condition group to check.
+ * @param array $tables
+ *   The tables from the related select query.
+ *
+ * @see \Drupal\Core\Database\Query\SelectInterface::getTables
+ *
+ * @return bool
+ *   Whether the conditions contain any condition using the reusable field.
+ */
+function _block_content_has_reusable_condition(array $condition, array $tables) {
+  // If this is a condition group call this function recursively for each nested
+  // condition until a condition is found that return TRUE.
+  if (isset($condition['#conjunction'])) {
+    foreach (array_filter($condition, 'is_array') as $nested_condition) {
+      if (_block_content_has_reusable_condition($nested_condition, $tables)) {
+        return TRUE;
+      }
+    }
+    return FALSE;
+  }
+  if (isset($condition['field'])) {
+    $field = $condition['field'];
+    if (is_object($field) && $field instanceof ConditionInterface) {
+      return _block_content_has_reusable_condition($field->conditions(), $tables);
+    }
+    $field_parts = explode('.', $field);
+    $data_table = \Drupal::entityTypeManager()->getDefinition('block_content')->getDataTable();
+    foreach ($tables as $table) {
+      if ($table['table'] === $data_table && $field_parts[0] === $table['alias'] && $field_parts[1] === 'reusable') {
+        return TRUE;
+      }
+    }
+
+  }
+  return FALSE;
+}
diff --git a/core/modules/block_content/block_content.post_update.php b/core/modules/block_content/block_content.post_update.php
new file mode 100644
index 0000000000000000000000000000000000000000..6587658d49e2e8a15177e50eedda672f32c071a0
--- /dev/null
+++ b/core/modules/block_content/block_content.post_update.php
@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * @file
+ * Post update functions for Custom Block.
+ */
+
+use Drupal\Core\Config\Entity\ConfigEntityUpdater;
+
+/**
+ * Adds a 'reusable' filter to all Custom Block views.
+ */
+function block_content_post_update_add_views_reusable_filter(&$sandbox = NULL) {
+  $data_table = \Drupal::entityTypeManager()
+    ->getDefinition('block_content')
+    ->getDataTable();
+
+  \Drupal::classResolver(ConfigEntityUpdater::class)->update($sandbox, 'view', function ($view) use ($data_table) {
+    /** @var \Drupal\views\ViewEntityInterface $view */
+    if ($view->get('base_table') != $data_table) {
+      return FALSE;
+    }
+    $save_view = FALSE;
+    $displays = $view->get('display');
+    foreach ($displays as $display_name => &$display) {
+      // Update the default display and displays that have overridden filters.
+      if (!isset($display['display_options']['filters']['reusable']) &&
+        ($display_name === 'default' || isset($display['display_options']['filters']))) {
+        $display['display_options']['filters']['reusable'] = [
+          'id' => 'reusable',
+          'plugin_id' => 'boolean',
+          'table' => $data_table,
+          'field' => 'reusable',
+          'value' => '1',
+          'entity_type' => 'block_content',
+          'entity_field' => 'reusable',
+        ];
+        $save_view = TRUE;
+      }
+    }
+    if ($save_view) {
+      $view->set('display', $displays);
+    }
+    return $save_view;
+  });
+}
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 1be5a0417c12d01b9e081da6b74b739cb90f9e81..2c008864f32e0a6cbdc448d93d18eaf4d86ea4c0 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
@@ -431,6 +431,44 @@ display:
           entity_type: block_content
           entity_field: type
           plugin_id: bundle
+        reusable:
+          id: reusable
+          table: block_content_field_data
+          field: reusable
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: '='
+          value: '1'
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: block_content
+          entity_field: reusable
+          plugin_id: boolean
       sorts: {  }
       title: 'Custom block library'
       header: {  }
diff --git a/core/modules/block_content/src/Access/AccessGroupAnd.php b/core/modules/block_content/src/Access/AccessGroupAnd.php
new file mode 100644
index 0000000000000000000000000000000000000000..7bb62bce0586111ffa28e4b463ca5372c47f6ae0
--- /dev/null
+++ b/core/modules/block_content/src/Access/AccessGroupAnd.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace Drupal\block_content\Access;
+
+use Drupal\Core\Access\AccessibleInterface;
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * An access group where all the dependencies must be allowed.
+ *
+ * @internal
+ */
+class AccessGroupAnd implements AccessibleInterface {
+
+
+  /**
+   * The access dependencies.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface[]
+   */
+  protected $dependencies = [];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addDependency(AccessibleInterface $dependency) {
+    $this->dependencies[] = $dependency;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function access($operation, AccountInterface $account = NULL, $return_as_object = FALSE) {
+    $access_result = AccessResult::neutral();
+    foreach (array_slice($this->dependencies, 1) as $dependency) {
+      $access_result = $access_result->andIf($dependency->access($operation, $account, TRUE));
+    }
+    return $return_as_object ? $access_result : $access_result->isAllowed();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDependencies() {
+    return $this->dependencies;
+  }
+
+}
diff --git a/core/modules/block_content/src/Access/DependentAccessInterface.php b/core/modules/block_content/src/Access/DependentAccessInterface.php
new file mode 100644
index 0000000000000000000000000000000000000000..bc6a6dcec694b58b0963a29de0cd83b9fc40a1d8
--- /dev/null
+++ b/core/modules/block_content/src/Access/DependentAccessInterface.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace Drupal\block_content\Access;
+
+/**
+ * Interface for AccessibleInterface objects that have an access dependency.
+ *
+ * Objects should implement this interface when their access depends on access
+ * to another object that implements \Drupal\Core\Access\AccessibleInterface.
+ * This interface simply provides the getter method for the access
+ * dependency object. Objects that implement this interface are responsible for
+ * checking access of the access dependency because the dependency may not take
+ * effect in all cases. For instance an entity may only need the access
+ * dependency set when it is embedded within another entity and its access
+ * should be dependent on access to the entity in which it is embedded.
+ *
+ * To check the access to the dependency the object implementing this interface
+ * can use code like this:
+ * @code
+ * $accessible->getAccessDependency()->access($op, $account, TRUE);
+ * @endcode
+ *
+ * @internal
+ */
+interface DependentAccessInterface {
+
+  /**
+   * Gets the access dependency.
+   *
+   * @return \Drupal\Core\Access\AccessibleInterface|null
+   *   The access dependency or NULL if none has been set.
+   */
+  public function getAccessDependency();
+
+}
diff --git a/core/modules/block_content/src/Access/RefinableDependentAccessInterface.php b/core/modules/block_content/src/Access/RefinableDependentAccessInterface.php
new file mode 100644
index 0000000000000000000000000000000000000000..469de52b8a2c66d1bdb344038614e3102f55f648
--- /dev/null
+++ b/core/modules/block_content/src/Access/RefinableDependentAccessInterface.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace Drupal\block_content\Access;
+
+use Drupal\Core\Access\AccessibleInterface;
+
+/**
+ * An interface to allow adding an access dependency.
+ *
+ * @internal
+ */
+interface RefinableDependentAccessInterface extends DependentAccessInterface {
+
+  /**
+   * Sets the access dependency.
+   *
+   * If an access dependency is already set this will replace the existing
+   * dependency.
+   *
+   * @param \Drupal\Core\Access\AccessibleInterface $access_dependency
+   *   The object upon which access depends.
+   *
+   * @return $this
+   */
+  public function setAccessDependency(AccessibleInterface $access_dependency);
+
+  /**
+   * Adds an access dependency into the existing access dependency.
+   *
+   * If no existing dependency is currently set this will set the dependency
+   * will be set to the new value.
+   *
+   * If there is an existing dependency and it is not an instance of
+   * AccessGroupAnd the dependency will be set as a new AccessGroupAnd
+   * instance with the existing and new dependencies as the members of the
+   * group.
+   *
+   * If there is an existing dependency and it is a instance of AccessGroupAnd
+   * the dependency will be added to the existing access group.
+   *
+   * @param \Drupal\Core\Access\AccessibleInterface $access_dependency
+   *   The access dependency to merge.
+   *
+   * @return $this
+   */
+  public function addAccessDependency(AccessibleInterface $access_dependency);
+
+}
diff --git a/core/modules/block_content/src/Access/RefinableDependentAccessTrait.php b/core/modules/block_content/src/Access/RefinableDependentAccessTrait.php
new file mode 100644
index 0000000000000000000000000000000000000000..98b2a547ccfb977cfb3709c1adda2505f8d90a99
--- /dev/null
+++ b/core/modules/block_content/src/Access/RefinableDependentAccessTrait.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\block_content\Access;
+
+use Drupal\Core\Access\AccessibleInterface;
+
+/**
+ * Trait for \Drupal\block_content\Access\RefinableDependentAccessInterface.
+ *
+ * @internal
+ */
+trait RefinableDependentAccessTrait {
+
+  /**
+   * The access dependency.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface
+   */
+  protected $accessDependency;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setAccessDependency(AccessibleInterface $access_dependency) {
+    $this->accessDependency = $access_dependency;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getAccessDependency() {
+    return $this->accessDependency;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addAccessDependency(AccessibleInterface $access_dependency) {
+    if (empty($this->accessDependency)) {
+      $this->accessDependency = $access_dependency;
+      return $this;
+    }
+    if (!$this->accessDependency instanceof AccessGroupAnd) {
+      $accessGroup = new AccessGroupAnd();
+      $this->accessDependency = $accessGroup->addDependency($this->accessDependency);
+    }
+    $this->accessDependency->addDependency($access_dependency);
+    return $this;
+  }
+
+}
diff --git a/core/modules/block_content/src/BlockContentAccessControlHandler.php b/core/modules/block_content/src/BlockContentAccessControlHandler.php
index 7079ef48495181081194a601eaab7c581643c176..17e61dce6b950966b32b75d4b3ac3f7aeae58123 100644
--- a/core/modules/block_content/src/BlockContentAccessControlHandler.php
+++ b/core/modules/block_content/src/BlockContentAccessControlHandler.php
@@ -2,27 +2,85 @@
 
 namespace Drupal\block_content;
 
+use Drupal\block_content\Access\DependentAccessInterface;
+use Drupal\block_content\Event\BlockContentGetDependencyEvent;
 use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityHandlerInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Entity\EntityTypeInterface;
 use Drupal\Core\Session\AccountInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 
 /**
  * Defines the access control handler for the custom block entity type.
  *
  * @see \Drupal\block_content\Entity\BlockContent
  */
-class BlockContentAccessControlHandler extends EntityAccessControlHandler {
+class BlockContentAccessControlHandler extends EntityAccessControlHandler implements EntityHandlerInterface {
+
+  /**
+   * The event dispatcher.
+   *
+   * @var \Symfony\Component\EventDispatcher\EventDispatcherInterface
+   */
+  protected $eventDispatcher;
+
+  /**
+   * BlockContentAccessControlHandler constructor.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type.
+   * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $dispatcher
+   *   The event dispatcher.
+   */
+  public function __construct(EntityTypeInterface $entity_type, EventDispatcherInterface $dispatcher) {
+    parent::__construct($entity_type);
+    $this->eventDispatcher = $dispatcher;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
+    return new static(
+      $entity_type,
+      $container->get('event_dispatcher')
+    );
+  }
 
   /**
    * {@inheritdoc}
    */
   protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
     if ($operation === 'view') {
-      return AccessResult::allowedIf($entity->isPublished())->addCacheableDependency($entity)
+      $access = AccessResult::allowedIf($entity->isPublished())->addCacheableDependency($entity)
         ->orIf(AccessResult::allowedIfHasPermission($account, 'administer blocks'));
     }
-    return parent::checkAccess($entity, $operation, $account);
+    else {
+      $access = parent::checkAccess($entity, $operation, $account);
+    }
+    $access->addCacheableDependency($entity);
+    /** @var \Drupal\block_content\BlockContentInterface $entity */
+    if ($entity->isReusable() === FALSE) {
+      if (!$entity instanceof DependentAccessInterface) {
+        throw new \LogicException("Non-reusable block entities must implement \Drupal\block_content\Access\DependentAccessInterface for access control.");
+      }
+      $dependency = $entity->getAccessDependency();
+      if (empty($dependency)) {
+        // If an access dependency has not been set let modules set one.
+        $event = new BlockContentGetDependencyEvent($entity);
+        $this->eventDispatcher->dispatch(BlockContentEvents::BLOCK_CONTENT_GET_DEPENDENCY, $event);
+        $dependency = $event->getAccessDependency();
+        if (empty($dependency)) {
+          return AccessResult::forbidden("Non-reusable blocks must set an access dependency for access control.");
+        }
+      }
+      /** @var \Drupal\Core\Entity\EntityInterface $dependency */
+      $access = $access->andIf($dependency->access($operation, $account, TRUE));
+    }
+    return $access;
   }
 
 }
diff --git a/core/modules/block_content/src/BlockContentEvents.php b/core/modules/block_content/src/BlockContentEvents.php
new file mode 100644
index 0000000000000000000000000000000000000000..85931b7a726befb828010f8ab9d5f7f37cf1a9ca
--- /dev/null
+++ b/core/modules/block_content/src/BlockContentEvents.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\block_content;
+
+/**
+ * Defines events for the block_content module.
+ *
+ * @see \Drupal\block_content\Event\BlockContentGetDependencyEvent
+ *
+ * @internal
+ */
+final class BlockContentEvents {
+
+  /**
+   * Name of the event when getting the dependency of a non-reusable block.
+   *
+   * This event allows modules to provide a dependency for non-reusable block
+   * access if
+   * \Drupal\block_content\Access\DependentAccessInterface::getAccessDependency()
+   * did not return a dependency during access checking.
+   *
+   * @Event
+   *
+   * @see \Drupal\block_content\Event\BlockContentGetDependencyEvent
+   * @see \Drupal\block_content\BlockContentAccessControlHandler::checkAccess()
+   *
+   * @var string
+   */
+  const BLOCK_CONTENT_GET_DEPENDENCY = 'block_content.get_dependency';
+
+}
diff --git a/core/modules/block_content/src/BlockContentInterface.php b/core/modules/block_content/src/BlockContentInterface.php
index 75fdc5979b389de4281121192f486b225b1beba9..bba6e4663d5bc9d29bbd898ec9fbfaeeba21d5e9 100644
--- a/core/modules/block_content/src/BlockContentInterface.php
+++ b/core/modules/block_content/src/BlockContentInterface.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\block_content;
 
+use Drupal\block_content\Access\RefinableDependentAccessInterface;
 use Drupal\Core\Entity\ContentEntityInterface;
 use Drupal\Core\Entity\EntityChangedInterface;
 use Drupal\Core\Entity\EntityPublishedInterface;
@@ -10,7 +11,7 @@
 /**
  * Provides an interface defining a custom block entity.
  */
-interface BlockContentInterface extends ContentEntityInterface, EntityChangedInterface, RevisionLogInterface, EntityPublishedInterface {
+interface BlockContentInterface extends ContentEntityInterface, EntityChangedInterface, RevisionLogInterface, EntityPublishedInterface, RefinableDependentAccessInterface {
 
   /**
    * Returns the block revision log message.
@@ -48,6 +49,28 @@ public function setInfo($info);
    */
   public function setRevisionLog($revision_log);
 
+  /**
+   * Determines if the block is reusable or not.
+   *
+   * @return bool
+   *   Returns TRUE if reusable and FALSE otherwise.
+   */
+  public function isReusable();
+
+  /**
+   * Sets the block to be reusable.
+   *
+   * @return $this
+   */
+  public function setReusable();
+
+  /**
+   * Sets the block to be non-reusable.
+   *
+   * @return $this
+   */
+  public function setNonReusable();
+
   /**
    * Sets the theme value.
    *
diff --git a/core/modules/block_content/src/BlockContentListBuilder.php b/core/modules/block_content/src/BlockContentListBuilder.php
index 7a4bdfc4c809b5e14db0717edf50fc75ca6bb95d..f254a764dc1dcc004c07ee66b09927d5d3ef4091 100644
--- a/core/modules/block_content/src/BlockContentListBuilder.php
+++ b/core/modules/block_content/src/BlockContentListBuilder.php
@@ -28,4 +28,19 @@ public function buildRow(EntityInterface $entity) {
     return $row + parent::buildRow($entity);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function getEntityIds() {
+    $query = $this->getStorage()->getQuery()
+      ->sort($this->entityType->getKey('id'));
+    $query->condition('reusable', TRUE);
+
+    // Only add the pager if a limit is specified.
+    if ($this->limit) {
+      $query->pager($this->limit);
+    }
+    return $query->execute();
+  }
+
 }
diff --git a/core/modules/block_content/src/BlockContentViewsData.php b/core/modules/block_content/src/BlockContentViewsData.php
index 010ede0ea59ad468488e991bc0511c5fd2136b38..e9ff0eb4cd83d1e777aa3ee849a80c1d0823c3d8 100644
--- a/core/modules/block_content/src/BlockContentViewsData.php
+++ b/core/modules/block_content/src/BlockContentViewsData.php
@@ -23,6 +23,8 @@ public function getViewsData() {
 
     $data['block_content_field_data']['type']['field']['id'] = 'field';
 
+    $data['block_content_field_data']['table']['wizard_id'] = 'block_content';
+
     $data['block_content']['block_content_listing_empty'] = [
       'title' => $this->t('Empty block library behavior'),
       'help' => $this->t('Provides a link to add a new block.'),
diff --git a/core/modules/block_content/src/Entity/BlockContent.php b/core/modules/block_content/src/Entity/BlockContent.php
index 7696da091e0368d786152855aa594228664ed698..b9bc8a9d2dfef9d3eedfc43646072dc7061a667c 100644
--- a/core/modules/block_content/src/Entity/BlockContent.php
+++ b/core/modules/block_content/src/Entity/BlockContent.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\block_content\Entity;
 
+use Drupal\block_content\Access\RefinableDependentAccessTrait;
 use Drupal\Core\Entity\EditorialContentEntityBase;
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\Core\Entity\EntityTypeInterface;
@@ -77,6 +78,8 @@
  */
 class BlockContent extends EditorialContentEntityBase implements BlockContentInterface {
 
+  use RefinableDependentAccessTrait;
+
   /**
    * The theme the block is being created in.
    *
@@ -118,7 +121,9 @@ public function getTheme() {
    */
   public function postSave(EntityStorageInterface $storage, $update = TRUE) {
     parent::postSave($storage, $update);
-    static::invalidateBlockPluginCache();
+    if ($this->isReusable() || (isset($this->original) && $this->original->isReusable())) {
+      static::invalidateBlockPluginCache();
+    }
   }
 
   /**
@@ -126,7 +131,14 @@ public function postSave(EntityStorageInterface $storage, $update = TRUE) {
    */
   public static function postDelete(EntityStorageInterface $storage, array $entities) {
     parent::postDelete($storage, $entities);
-    static::invalidateBlockPluginCache();
+    /** @var \Drupal\block_content\BlockContentInterface $block */
+    foreach ($entities as $block) {
+      if ($block->isReusable()) {
+        // If any deleted blocks are reusable clear the block cache.
+        static::invalidateBlockPluginCache();
+        return;
+      }
+    }
   }
 
   /**
@@ -200,6 +212,14 @@ public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
       ->setTranslatable(TRUE)
       ->setRevisionable(TRUE);
 
+    $fields['reusable'] = BaseFieldDefinition::create('boolean')
+      ->setLabel(t('Reusable'))
+      ->setDescription(t('A boolean indicating whether this block is reusable.'))
+      ->setTranslatable(FALSE)
+      ->setRevisionable(FALSE)
+      ->setDefaultValue(TRUE)
+      ->setInitialValue(TRUE);
+
     return $fields;
   }
 
@@ -282,6 +302,27 @@ public function setRevisionLogMessage($revision_log_message) {
     return $this;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isReusable() {
+    return $this->get('reusable')->first()->get('value')->getCastedValue();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setReusable() {
+    return $this->set('reusable', TRUE);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setNonReusable() {
+    return $this->set('reusable', FALSE);
+  }
+
   /**
    * Invalidates the block plugin cache after changes and deletions.
    */
diff --git a/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php b/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php
new file mode 100644
index 0000000000000000000000000000000000000000..e705172aa523b97126626f5bd218b3bf49446014
--- /dev/null
+++ b/core/modules/block_content/src/Event/BlockContentGetDependencyEvent.php
@@ -0,0 +1,70 @@
+<?php
+
+namespace Drupal\block_content\Event;
+
+use Drupal\block_content\BlockContentInterface;
+use Drupal\Core\Access\AccessibleInterface;
+use Symfony\Component\EventDispatcher\Event;
+
+/**
+ * Block content event to allow setting an access dependency.
+ *
+ * @internal
+ */
+class BlockContentGetDependencyEvent extends Event {
+
+  /**
+   * The block content entity.
+   *
+   * @var \Drupal\block_content\BlockContentInterface
+   */
+  protected $blockContent;
+
+  /**
+   * The dependency.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface
+   */
+  protected $accessDependency;
+
+  /**
+   * BlockContentGetDependencyEvent constructor.
+   *
+   * @param \Drupal\block_content\BlockContentInterface $blockContent
+   *   The block content entity.
+   */
+  public function __construct(BlockContentInterface $blockContent) {
+    $this->blockContent = $blockContent;
+  }
+
+  /**
+   * Gets the block content entity.
+   *
+   * @return \Drupal\block_content\BlockContentInterface
+   *   The block content entity.
+   */
+  public function getBlockContentEntity() {
+    return $this->blockContent;
+  }
+
+  /**
+   * Gets the access dependency.
+   *
+   * @return \Drupal\Core\Access\AccessibleInterface
+   *   The access dependency.
+   */
+  public function getAccessDependency() {
+    return $this->accessDependency;
+  }
+
+  /**
+   * Sets the access dependency.
+   *
+   * @param \Drupal\Core\Access\AccessibleInterface $access_dependency
+   *   The access dependency.
+   */
+  public function setAccessDependency(AccessibleInterface $access_dependency) {
+    $this->accessDependency = $access_dependency;
+  }
+
+}
diff --git a/core/modules/block_content/src/Plugin/Derivative/BlockContent.php b/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
index ac82a6c39caa0b55512983d3f5bf85552f5625e6..ba1ab989688a7d03ff32a7b01971875afd4db834 100644
--- a/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
+++ b/core/modules/block_content/src/Plugin/Derivative/BlockContent.php
@@ -43,7 +43,7 @@ public static function create(ContainerInterface $container, $base_plugin_id) {
    * {@inheritdoc}
    */
   public function getDerivativeDefinitions($base_plugin_definition) {
-    $block_contents = $this->blockContentStorage->loadMultiple();
+    $block_contents = $this->blockContentStorage->loadByProperties(['reusable' => TRUE]);
     // Reset the discovered definitions.
     $this->derivatives = [];
     /** @var $block_content \Drupal\block_content\Entity\BlockContent */
diff --git a/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php b/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php
new file mode 100644
index 0000000000000000000000000000000000000000..60725015374636a68d1d93879783043c990395fe
--- /dev/null
+++ b/core/modules/block_content/src/Plugin/views/wizard/BlockContent.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace Drupal\block_content\Plugin\views\wizard;
+
+use Drupal\views\Plugin\views\wizard\WizardPluginBase;
+
+/**
+ * Used for creating 'block_content' views with the wizard.
+ *
+ * @ViewsWizard(
+ *   id = "block_content",
+ *   base_table = "block_content_field_data",
+ *   title = @Translation("Custom Block"),
+ * )
+ */
+class BlockContent extends WizardPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFilters() {
+    $filters = parent::getFilters();
+    $filters['reusable'] = [
+      'id' => 'reusable',
+      'plugin_id' => 'boolean',
+      'table' => $this->base_table,
+      'field' => 'reusable',
+      'value' => '1',
+      'entity_type' => $this->entityTypeId,
+      'entity_field' => 'reusable',
+    ];
+    return $filters;
+  }
+
+}
diff --git a/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php b/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php
new file mode 100644
index 0000000000000000000000000000000000000000..1a46c486c230b0f239ee98809f822d12c29ab788
--- /dev/null
+++ b/core/modules/block_content/tests/modules/block_content_test/src/Plugin/EntityReferenceSelection/TestSelection.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Drupal\block_content_test\Plugin\EntityReferenceSelection;
+
+use Drupal\Core\Entity\Plugin\EntityReferenceSelection\DefaultSelection;
+
+/**
+ * Test EntityReferenceSelection with conditions on the 'reusable' field.
+ */
+class TestSelection extends DefaultSelection {
+
+  /**
+   * The condition type.
+   *
+   * @var string
+   */
+  protected $conditionType;
+
+  /**
+   * Whether to set the condition for reusable or non-reusable blocks.
+   *
+   * @var bool
+   */
+  protected $isReusable;
+
+  /**
+   * Sets the test mode.
+   *
+   * @param string $condition_type
+   *   The condition type.
+   * @param bool $is_reusable
+   *   Whether to set the condition for reusable or non-reusable blocks.
+   */
+  public function setTestMode($condition_type = NULL, $is_reusable = NULL) {
+    $this->conditionType = $condition_type;
+    $this->isReusable = $is_reusable;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function buildEntityQuery($match = NULL, $match_operator = 'CONTAINS') {
+    $query = parent::buildEntityQuery($match, $match_operator);
+    if ($this->conditionType) {
+      /** @var \Drupal\Core\Database\Query\ConditionInterface $add_condition */
+      $add_condition = NULL;
+      switch ($this->conditionType) {
+        case 'base':
+          $add_condition = $query;
+          break;
+
+        case 'group':
+          $group = $query->andConditionGroup()
+            ->exists('type');
+          $add_condition = $group;
+          $query->condition($group);
+          break;
+
+        case "nested_group":
+          $query->exists('type');
+          $sub_group = $query->andConditionGroup()
+            ->exists('type');
+          $add_condition = $sub_group;
+          $group = $query->andConditionGroup()
+            ->exists('type')
+            ->condition($sub_group);
+          $query->condition($group);
+          break;
+      }
+      if ($this->isReusable) {
+        $add_condition->condition('reusable', 1);
+      }
+      else {
+        $add_condition->condition('reusable', 0);
+      }
+    }
+    return $query;
+  }
+
+}
diff --git a/core/modules/block_content/tests/modules/block_content_view_override/block_content_view_override.info.yml b/core/modules/block_content/tests/modules/block_content_view_override/block_content_view_override.info.yml
new file mode 100644
index 0000000000000000000000000000000000000000..3ca2d1bc375d2b05d8be7503ee03ede71643dc9e
--- /dev/null
+++ b/core/modules/block_content/tests/modules/block_content_view_override/block_content_view_override.info.yml
@@ -0,0 +1,9 @@
+name: "Custom Block module reusable tests"
+type: module
+description: "Support module for custom block reusable testing."
+package: Testing
+version: VERSION
+core: 8.x
+dependencies:
+  - drupal:block_content
+  - drupal:views
diff --git a/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml b/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml
new file mode 100644
index 0000000000000000000000000000000000000000..3c622a9abb42918cf149a0f42988dfd6bb08dd1f
--- /dev/null
+++ b/core/modules/block_content/tests/modules/block_content_view_override/config/install/views.view.block_content.yml
@@ -0,0 +1,602 @@
+langcode: en
+status: true
+dependencies:
+  module:
+    - block_content
+    - user
+id: block_content
+label: 'Custom block library'
+module: views
+description: 'Find and manage custom blocks.'
+tag: default
+base_table: block_content_field_data
+base_field: id
+core: 8.x
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Master
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'administer blocks'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: mini
+        options:
+          items_per_page: 50
+          offset: 0
+          id: 0
+          total_pages: null
+          tags:
+            previous: '‹ Previous'
+            next: 'Next ›'
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+      style:
+        type: table
+        options:
+          grouping: {  }
+          row_class: ''
+          default_row_class: true
+          override: true
+          sticky: false
+          caption: ''
+          summary: ''
+          description: ''
+          columns:
+            info: info
+            type: type
+            changed: changed
+            operations: operations
+          info:
+            info:
+              sortable: true
+              default_sort_order: asc
+              align: ''
+              separator: ''
+              empty_column: false
+              responsive: ''
+            type:
+              sortable: true
+              default_sort_order: asc
+              align: ''
+              separator: ''
+              empty_column: false
+              responsive: ''
+            changed:
+              sortable: true
+              default_sort_order: desc
+              align: ''
+              separator: ''
+              empty_column: false
+              responsive: ''
+            operations:
+              sortable: false
+              default_sort_order: asc
+              align: ''
+              separator: ''
+              empty_column: false
+              responsive: ''
+          default: changed
+          empty_table: true
+      row:
+        type: fields
+      fields:
+        info:
+          id: info
+          table: block_content_field_data
+          field: info
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: 'Block description'
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          click_sort_column: value
+          type: string
+          settings:
+            link_to_entity: true
+          group_column: value
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          entity_type: null
+          entity_field: info
+          plugin_id: field
+        type:
+          id: type
+          table: block_content_field_data
+          field: type
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: 'Block type'
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          click_sort_column: target_id
+          type: entity_reference_label
+          settings:
+            link: false
+          group_column: target_id
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          entity_type: block_content
+          entity_field: type
+          plugin_id: field
+        changed:
+          id: changed
+          table: block_content_field_data
+          field: changed
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: Updated
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          entity_type: block_content
+          entity_field: changed
+          type: timestamp
+          settings:
+            date_format: short
+            custom_date_format: ''
+            timezone: ''
+          plugin_id: field
+        operations:
+          id: operations
+          table: block_content
+          field: operations
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: Operations
+          exclude: false
+          alter:
+            alter_text: false
+            text: ''
+            make_link: false
+            path: ''
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: true
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          destination: true
+          entity_type: block_content
+          plugin_id: entity_operations
+      filters:
+        info:
+          id: info
+          table: block_content_field_data
+          field: info
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: contains
+          value: ''
+          group: 1
+          exposed: true
+          expose:
+            operator_id: info_op
+            label: 'Block description'
+            description: ''
+            use_operator: false
+            operator: info_op
+            identifier: info
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+              anonymous: '0'
+              administrator: '0'
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: block_content
+          entity_field: info
+          plugin_id: string
+        type:
+          id: type
+          table: block_content_field_data
+          field: type
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: in
+          value: {  }
+          group: 1
+          exposed: true
+          expose:
+            operator_id: type_op
+            label: 'Block type'
+            description: ''
+            use_operator: false
+            operator: type_op
+            identifier: type
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+              anonymous: '0'
+              administrator: '0'
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: block_content
+          entity_field: type
+          plugin_id: bundle
+      sorts: {  }
+      title: 'Custom block library'
+      header: {  }
+      footer: {  }
+      empty:
+        area_text_custom:
+          id: area_text_custom
+          table: views
+          field: area_text_custom
+          relationship: none
+          group_type: group
+          admin_label: ''
+          empty: true
+          tokenize: false
+          content: 'There are no custom blocks available.'
+          plugin_id: text_custom
+        block_content_listing_empty:
+          admin_label: ''
+          empty: true
+          field: block_content_listing_empty
+          group_type: group
+          id: block_content_listing_empty
+          label: ''
+          relationship: none
+          table: block_content
+          plugin_id: block_content_listing_empty
+          entity_type: block_content
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user.permissions
+      max-age: 0
+      tags: {  }
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: admin/structure/block/block-content
+      menu:
+        type: tab
+        title: 'Custom block library'
+        description: ''
+        parent: block.admin_display
+        weight: 0
+        context: '0'
+        menu_name: admin
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user.permissions
+      max-age: 0
+      tags: {  }
+  page_2:
+    display_plugin: page
+    id: page_2
+    display_title: 'Page 2'
+    position: 2
+    display_options:
+      display_extenders: {  }
+      path: extra-view-display
+      filters:
+        type:
+          id: type
+          table: block_content_field_data
+          field: type
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: in
+          value: {  }
+          group: 1
+          exposed: true
+          expose:
+            operator_id: type_op
+            label: 'Block type'
+            description: ''
+            use_operator: false
+            operator: type_op
+            identifier: type
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+              anonymous: '0'
+              administrator: '0'
+            reduce: false
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: block_content
+          entity_field: type
+          plugin_id: bundle
+        info:
+          id: info
+          table: block_content_field_data
+          field: info
+          relationship: none
+          group_type: group
+          admin_label: ''
+          operator: 'contains'
+          value: block2
+          group: 1
+          exposed: false
+          expose:
+            operator_id: ''
+            label: ''
+            description: ''
+            use_operator: false
+            operator: ''
+            identifier: ''
+            required: false
+            remember: false
+            multiple: false
+            remember_roles:
+              authenticated: authenticated
+            placeholder: ''
+          is_grouped: false
+          group_info:
+            label: ''
+            description: ''
+            identifier: ''
+            optional: true
+            widget: select
+            multiple: false
+            remember: false
+            default_group: All
+            default_group_multiple: {  }
+            group_items: {  }
+          entity_type: block_content
+          entity_field: info
+          plugin_id: string
+      defaults:
+        filters: false
+        filter_groups: false
+      filter_groups:
+        operator: AND
+        groups:
+          1: AND
+    cache_metadata:
+      max-age: 0
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url
+        - url.query_args
+        - user.permissions
+      tags: {  }
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
index 9a26f1c4077616b59aee55e8a21686a4a3f850c4..8919c05d00193c6354d84979aaa116725d35f1ce 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\block_content\Functional;
 
+use Drupal\block_content\Entity\BlockContent;
+
 /**
  * Tests the listing of custom blocks.
  *
@@ -104,6 +106,19 @@ public function testListing() {
 
     // Confirm that the empty text is displayed.
     $this->assertText(t('There are no custom blocks yet.'));
+
+    $block_content = BlockContent::create([
+      'info' => 'Non-reusable block',
+      'type' => 'basic',
+      'reusable' => FALSE,
+    ]);
+    $block_content->save();
+
+    $this->drupalGet('admin/structure/block/block-content');
+    // Confirm that the empty text is displayed.
+    $this->assertSession()->pageTextContains('There are no custom blocks yet.');
+    // Confirm the non-reusable block is not on the page.
+    $this->assertSession()->pageTextNotContains('Non-reusable block');
   }
 
 }
diff --git a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
index 1c623be82eba3c9cf4af6525a00f07fa3971df37..f9cf29eb77bcc20ea4c47a4871c3f2d10d25ab9e 100644
--- a/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
+++ b/core/modules/block_content/tests/src/Functional/BlockContentListViewsTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\block_content\Functional;
 
+use Drupal\block_content\Entity\BlockContent;
+
 /**
  * Tests the Views-powered listing of custom blocks.
  *
@@ -112,6 +114,19 @@ public function testListing() {
     // Confirm that the empty text is displayed.
     $this->assertText('There are no custom blocks available.');
     $this->assertLink('custom block');
+
+    $block_content = BlockContent::create([
+      'info' => 'Non-reusable block',
+      'type' => 'basic',
+      'reusable' => FALSE,
+    ]);
+    $block_content->save();
+
+    $this->drupalGet('admin/structure/block/block-content');
+    // Confirm that the empty text is displayed.
+    $this->assertSession()->pageTextContains('There are no custom blocks available.');
+    // Confirm the non-reusable block is not on the page.
+    $this->assertSession()->pageTextNotContains('Non-reusable block');
   }
 
 }
diff --git a/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php b/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
index c77585eb292dca4650953bf8c9a59a39a61f7917..4a3ac11f4c5a71e448a48421057f1c9ef567bedc 100644
--- a/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
+++ b/core/modules/block_content/tests/src/Functional/Rest/BlockContentResourceTestBase.php
@@ -92,6 +92,11 @@ protected function getExpectedNormalizedEntity() {
           'value' => 'en',
         ],
       ],
+      'reusable' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
       'type' => [
         [
           'target_id' => 'basic',
diff --git a/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php b/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..4e8d99398b68060c647deb7f12878be160cd3984
--- /dev/null
+++ b/core/modules/block_content/tests/src/Functional/Update/BlockContentReusableUpdateTest.php
@@ -0,0 +1,155 @@
+<?php
+
+namespace Drupal\Tests\block_content\Functional\Update;
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+
+/**
+ * Tests 'reusable' field related update functions for the Block Content module.
+ *
+ * @group Update
+ * @group legacy
+ */
+class BlockContentReusableUpdateTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setDatabaseDumpFiles() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
+    ];
+  }
+
+  /**
+   * Tests adding 'reusable' entity base field to the block content entity type.
+   *
+   * @see block_content_update_8600
+   * @see block_content_post_update_add_views_reusable_filter
+   */
+  public function testReusableFieldAddition() {
+    $assert_session = $this->assertSession();
+    $entity_definition_update_manager = \Drupal::entityDefinitionUpdateManager();
+
+    // Delete custom block library view.
+    $this->config('views.view.block_content')->delete();
+    // Install the test module with the 'block_content' view with an extra
+    // display with overridden filters. This extra display should also have a
+    // filter added for 'reusable' field so that it does not expose non-reusable
+    // fields. This display also has a filter that only shows blocks that
+    // contain 'block2' in the 'info' field.
+    $this->container->get('module_installer')->install(['block_content_view_override']);
+
+    // Ensure that 'reusable' field is not present before updates.
+    $this->assertEmpty($entity_definition_update_manager->getFieldStorageDefinition('reusable', 'block_content'));
+
+    // Ensure that 'reusable' filter is not present before updates.
+    $view_config = \Drupal::configFactory()->get('views.view.block_content');
+    $this->assertFalse($view_config->isNew());
+    $this->assertEmpty($view_config->get('display.default.display_options.filters.reusable'));
+    $this->assertEmpty($view_config->get('display.page_2.display_options.filters.reusable'));
+    // Run updates.
+    $this->runUpdates();
+
+    // Ensure that 'reusable' filter is present after updates.
+    \Drupal::configFactory()->clearStaticCache();
+    $view_config = \Drupal::configFactory()->get('views.view.block_content');
+    $this->assertNotEmpty($view_config->get('display.default.display_options.filters.reusable'));
+    $this->assertNotEmpty($view_config->get('display.page_2.display_options.filters.reusable'));
+
+    // Check that the field exists and is configured correctly.
+    $reusable_field = $entity_definition_update_manager->getFieldStorageDefinition('reusable', 'block_content');
+    $this->assertEquals('Reusable', $reusable_field->getLabel());
+    $this->assertEquals('A boolean indicating whether this block is reusable.', $reusable_field->getDescription());
+    $this->assertEquals(FALSE, $reusable_field->isRevisionable());
+    $this->assertEquals(FALSE, $reusable_field->isTranslatable());
+
+    $after_block1 = BlockContent::create([
+      'info' => 'After update block1',
+      'type' => 'basic_block',
+    ]);
+    $after_block1->save();
+    // Add second block that will be shown with the 'info' filter on the
+    // additional view display.
+    $after_block2 = BlockContent::create([
+      'info' => 'After update block2',
+      'type' => 'basic_block',
+    ]);
+    $after_block2->save();
+
+    $this->assertTrue($after_block1->isReusable());
+    $this->assertTrue($after_block2->isReusable());
+
+    $admin_user = $this->drupalCreateUser(['administer blocks']);
+    $this->drupalLogin($admin_user);
+
+    $block_non_reusable = BlockContent::create([
+      'info' => 'block1 non reusable',
+      'type' => 'basic_block',
+      'reusable' => FALSE,
+    ]);
+    $block_non_reusable->save();
+    // Add second block that would be shown with the 'info' filter on the
+    // additional view display if the 'reusable' filter was not added.
+    $block2_non_reusable = BlockContent::create([
+      'info' => 'block2 non reusable',
+      'type' => 'basic_block',
+      'reusable' => FALSE,
+    ]);
+    $block2_non_reusable->save();
+    $this->assertFalse($block_non_reusable->isReusable());
+    $this->assertFalse($block2_non_reusable->isReusable());
+
+    // Ensure the Custom Block view shows the reusable blocks only.
+    $this->drupalGet('admin/structure/block/block-content');
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseContains('view-id-block_content');
+    $assert_session->pageTextContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_non_reusable->label());
+    $assert_session->pageTextNotContains($block2_non_reusable->label());
+
+    // Ensure the view's other display also only shows reusable blocks and still
+    // filters on the 'info' field.
+    $this->drupalGet('extra-view-display');
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseContains('view-id-block_content');
+    $assert_session->pageTextNotContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_non_reusable->label());
+    $assert_session->pageTextNotContains($block2_non_reusable->label());
+
+    // Ensure the Custom Block listing without Views installed shows the only
+    // reusable blocks.
+    $this->drupalGet('admin/structure/block/block-content');
+    $this->container->get('module_installer')->uninstall(['views_ui', 'views']);
+    $this->drupalGet('admin/structure/block/block-content');
+    $assert_session->statusCodeEquals('200');
+    $assert_session->responseNotContains('view-id-block_content');
+    $assert_session->pageTextContains($after_block1->label());
+    $assert_session->pageTextContains($after_block2->label());
+    $assert_session->pageTextNotContains($block_non_reusable->label());
+    $assert_session->pageTextNotContains($block2_non_reusable->label());
+
+    $this->drupalGet('block/' . $after_block1->id());
+    $assert_session->statusCodeEquals('200');
+
+    // Ensure the non-reusable block is not accessible in the form.
+    $this->drupalGet('block/' . $block_non_reusable->id());
+    $assert_session->statusCodeEquals('403');
+
+    $this->drupalLogout();
+
+    $this->drupalLogin($this->createUser([
+      'access user profiles',
+      'administer blocks',
+    ]));
+    $this->drupalGet('block/' . $after_block1->id());
+    $assert_session->statusCodeEquals('200');
+
+    $this->drupalGet('block/' . $block_non_reusable->id());
+    $assert_session->statusCodeEquals('403');
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..2c59e5c50fe84ec0c7888e02f0d84e0a7d273821
--- /dev/null
+++ b/core/modules/block_content/tests/src/Functional/Views/BlockContentWizardTest.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Drupal\Tests\block_content\Functional\Views;
+
+use Drupal\Tests\block_content\Functional\BlockContentTestBase;
+
+/**
+ * Tests block_content wizard and generic entity integration.
+ *
+ * @group block_content
+ */
+class BlockContentWizardTest extends BlockContentTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['block_content', 'views_ui'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->drupalLogin($this->drupalCreateUser(['administer views']));
+    $this->createBlockContentType('Basic block');
+  }
+
+  /**
+   * Tests creating a 'block_content' entity view.
+   */
+  public function testViewAddBlockContent() {
+    $view = [];
+    $view['label'] = $this->randomMachineName(16);
+    $view['id'] = strtolower($this->randomMachineName(16));
+    $view['description'] = $this->randomMachineName(16);
+    $view['page[create]'] = FALSE;
+    $view['show[wizard_key]'] = 'block_content';
+    $this->drupalPostForm('admin/structure/views/add', $view, t('Save and edit'));
+
+    $view_storage_controller = $this->container->get('entity_type.manager')->getStorage('view');
+    /** @var \Drupal\views\Entity\View $view */
+    $view = $view_storage_controller->load($view['id']);
+
+    $display_options = $view->getDisplay('default')['display_options'];
+
+    $this->assertEquals('block_content', $display_options['filters']['reusable']['entity_type']);
+    $this->assertEquals('reusable', $display_options['filters']['reusable']['entity_field']);
+    $this->assertEquals('boolean', $display_options['filters']['reusable']['plugin_id']);
+    $this->assertEquals('1', $display_options['filters']['reusable']['value']);
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Kernel/BlockContentAccessHandlerTest.php b/core/modules/block_content/tests/src/Kernel/BlockContentAccessHandlerTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..64b524d80b89273049ca86fed288b9b3d84bef62
--- /dev/null
+++ b/core/modules/block_content/tests/src/Kernel/BlockContentAccessHandlerTest.php
@@ -0,0 +1,300 @@
+<?php
+
+namespace Drupal\Tests\block_content\Kernel;
+
+use Drupal\block_content\BlockContentAccessControlHandler;
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\block_content\Entity\BlockContentType;
+use Drupal\Core\Access\AccessibleInterface;
+use Drupal\Core\Access\AccessResult;
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\user\Entity\Role;
+use Drupal\user\Entity\User;
+
+/**
+ * Tests the block content entity access handler.
+ *
+ * @coversDefaultClass \Drupal\block_content\BlockContentAccessControlHandler
+ *
+ * @group block_content
+ */
+class BlockContentAccessHandlerTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'block',
+    'block_content',
+    'system',
+    'user',
+  ];
+
+  /**
+   * The BlockContent access controller to test.
+   *
+   * @var \Drupal\block_content\BlockContentAccessControlHandler
+   */
+  protected $accessControlHandler;
+
+  /**
+   * The BlockContent entity used for testing.
+   *
+   * @var \Drupal\block_content\Entity\BlockContent
+   */
+  protected $blockEntity;
+
+  /**
+   * The test role.
+   *
+   * @var \Drupal\user\RoleInterface
+   */
+  protected $role;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installSchema('system', ['sequence']);
+    $this->installSchema('system', ['sequences']);
+    $this->installSchema('user', ['users_data']);
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('block_content');
+
+    // Create a block content type.
+    $block_content_type = BlockContentType::create([
+      'id' => 'square',
+      'label' => 'A square block type',
+      'description' => "Provides a block type that is square.",
+    ]);
+    $block_content_type->save();
+
+    $this->blockEntity = BlockContent::create([
+      'info' => 'The Block',
+      'type' => 'square',
+    ]);
+    $this->blockEntity->save();
+
+    // Create user 1 test does not have all permissions.
+    User::create([
+      'name' => 'admin',
+    ])->save();
+
+    $this->role = Role::create([
+      'id' => 'roly',
+      'label' => 'roly poly',
+    ]);
+    $this->role->save();
+    $this->accessControlHandler = new BlockContentAccessControlHandler(\Drupal::entityTypeManager()->getDefinition('block_content'), \Drupal::service('event_dispatcher'));
+  }
+
+  /**
+   * @covers ::checkAccess
+   *
+   * @dataProvider providerTestAccess
+   */
+  public function testAccess($operation, $published, $reusable, $permissions, $parent_access, $expected_access) {
+    $published ? $this->blockEntity->setPublished() : $this->blockEntity->setUnpublished();
+    $reusable ? $this->blockEntity->setReusable() : $this->blockEntity->setNonReusable();
+
+    $user = User::create([
+      'name' => 'Someone',
+      'mail' => 'hi@example.com',
+    ]);
+
+    if ($permissions) {
+      foreach ($permissions as $permission) {
+        $this->role->grantPermission($permission);
+      }
+      $this->role->save();
+    }
+    $user->addRole($this->role->id());
+    $user->save();
+
+    if ($parent_access) {
+      $parent_entity = $this->prophesize(AccessibleInterface::class);
+      $expected_parent_result = NULL;
+      switch ($parent_access) {
+        case 'allowed':
+          $expected_parent_result = AccessResult::allowed();
+          break;
+
+        case 'neutral':
+          $expected_parent_result = AccessResult::neutral();
+          break;
+
+        case 'forbidden':
+          $expected_parent_result = AccessResult::forbidden();
+          break;
+      }
+      $parent_entity->access($operation, $user, TRUE)
+        ->willReturn($expected_parent_result)
+        ->shouldBeCalled();
+
+      $this->blockEntity->setAccessDependency($parent_entity->reveal());
+
+    }
+    $this->blockEntity->save();
+
+    $result = $this->accessControlHandler->access($this->blockEntity, $operation, $user, TRUE);
+    switch ($expected_access) {
+      case 'allowed':
+        $this->assertTrue($result->isAllowed());
+        break;
+
+      case 'forbidden':
+        $this->assertTrue($result->isForbidden());
+        break;
+
+      case  'neutral':
+        $this->assertTrue($result->isNeutral());
+        break;
+
+      default:
+        $this->fail('Unexpected access type');
+    }
+  }
+
+  /**
+   * Dataprovider for testAccess().
+   */
+  public function providerTestAccess() {
+    $cases = [
+      'view:published:reusable' => [
+        'view',
+        TRUE,
+        TRUE,
+        [],
+        NULL,
+        'allowed',
+      ],
+      'view:unpublished:reusable' => [
+        'view',
+        FALSE,
+        TRUE,
+        [],
+        NULL,
+        'neutral',
+      ],
+      'view:unpublished:reusable:admin' => [
+        'view',
+        FALSE,
+        TRUE,
+        ['administer blocks'],
+        NULL,
+        'allowed',
+      ],
+      'view:published:reusable:admin' => [
+        'view',
+        TRUE,
+        TRUE,
+        ['administer blocks'],
+        NULL,
+        'allowed',
+      ],
+      'view:published:non_reusable' => [
+        'view',
+        TRUE,
+        FALSE,
+        [],
+        NULL,
+        'forbidden',
+      ],
+      'view:published:non_reusable:parent_allowed' => [
+        'view',
+        TRUE,
+        FALSE,
+        [],
+        'allowed',
+        'allowed',
+      ],
+      'view:published:non_reusable:parent_neutral' => [
+        'view',
+        TRUE,
+        FALSE,
+        [],
+        'neutral',
+        'neutral',
+      ],
+      'view:published:non_reusable:parent_forbidden' => [
+        'view',
+        TRUE,
+        FALSE,
+        [],
+        'forbidden',
+        'forbidden',
+      ],
+    ];
+    foreach (['update', 'delete'] as $operation) {
+      $cases += [
+        $operation . ':published:reusable' => [
+          $operation,
+          TRUE,
+          TRUE,
+          [],
+          NULL,
+          'neutral',
+        ],
+        $operation . ':unpublished:reusable' => [
+          $operation,
+          FALSE,
+          TRUE,
+          [],
+          NULL,
+          'neutral',
+        ],
+        $operation . ':unpublished:reusable:admin' => [
+          $operation,
+          FALSE,
+          TRUE,
+          ['administer blocks'],
+          NULL,
+          'allowed',
+        ],
+        $operation . ':published:reusable:admin' => [
+          $operation,
+          TRUE,
+          TRUE,
+          ['administer blocks'],
+          NULL,
+          'allowed',
+        ],
+        $operation . ':published:non_reusable' => [
+          $operation,
+          TRUE,
+          FALSE,
+          [],
+          NULL,
+          'forbidden',
+        ],
+        $operation . ':published:non_reusable:parent_allowed' => [
+          $operation,
+          TRUE,
+          FALSE,
+          [],
+          'allowed',
+          'neutral',
+        ],
+        $operation . ':published:non_reusable:parent_neutral' => [
+          $operation,
+          TRUE,
+          FALSE,
+          [],
+          'neutral',
+          'neutral',
+        ],
+        $operation . ':published:non_reusable:parent_forbidden' => [
+          $operation,
+          TRUE,
+          FALSE,
+          [],
+          'forbidden',
+          'forbidden',
+        ],
+      ];
+      return $cases;
+    }
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php b/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..d08d86f25fa8a86f23bbbafd0733d33bd75c0e24
--- /dev/null
+++ b/core/modules/block_content/tests/src/Kernel/BlockContentDeriverTest.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Drupal\Tests\block_content\Kernel;
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\block_content\Entity\BlockContentType;
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests block content plugin deriver.
+ *
+ * @group block_content
+ */
+class BlockContentDeriverTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['block', 'block_content', 'system', 'user'];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->installSchema('system', ['sequence']);
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('block_content');
+  }
+
+  /**
+   * Tests that only reusable blocks are derived.
+   */
+  public function testReusableBlocksOnlyAreDerived() {
+    // Create a block content type.
+    $block_content_type = BlockContentType::create([
+      'id' => 'spiffy',
+      'label' => 'Mucho spiffy',
+      'description' => "Provides a block type that increases your site's spiffiness by up to 11%",
+    ]);
+    $block_content_type->save();
+    // And a block content entity.
+    $block_content = BlockContent::create([
+      'info' => 'Spiffy prototype',
+      'type' => 'spiffy',
+    ]);
+    $block_content->save();
+
+    // Ensure the reusable block content is provided as a derivative block
+    // plugin.
+    /** @var \Drupal\Core\Block\BlockManagerInterface $block_manager */
+    $block_manager = $this->container->get('plugin.manager.block');
+    $plugin_id = 'block_content' . PluginBase::DERIVATIVE_SEPARATOR . $block_content->uuid();
+    $this->assertTrue($block_manager->hasDefinition($plugin_id));
+
+    // Set the block not to be reusable.
+    $block_content->setNonReusable();
+    $block_content->save();
+
+    // Ensure the non-reusable block content is not provided a derivative block
+    // plugin.
+    $this->assertFalse($block_manager->hasDefinition($plugin_id));
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php b/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..e593336fa3a1eff8526203a199679efb5bca1b56
--- /dev/null
+++ b/core/modules/block_content/tests/src/Kernel/BlockContentEntityReferenceSelectionTest.php
@@ -0,0 +1,189 @@
+<?php
+
+namespace Drupal\Tests\block_content\Kernel;
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\block_content\Entity\BlockContentType;
+use Drupal\block_content_test\Plugin\EntityReferenceSelection\TestSelection;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests EntityReference selection handlers don't return non-reusable blocks.
+ *
+ * @see block_content_query_entity_reference_alter()
+ *
+ * @group block_content
+ */
+class BlockContentEntityReferenceSelectionTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'block',
+    'block_content',
+    'block_content_test',
+    'system',
+    'user',
+  ];
+
+  /**
+   * The entity type manager.
+   *
+   * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+   */
+  protected $entityTypeManager;
+
+  /**
+   * Test reusable block.
+   *
+   * @var \Drupal\block_content\BlockContentInterface
+   */
+  protected $blockReusable;
+
+  /**
+   * Test non-reusable block.
+   *
+   * @var \Drupal\block_content\BlockContentInterface
+   */
+  protected $blockNonReusable;
+
+  /**
+   * Test selection handler.
+   *
+   * @var \Drupal\block_content_test\Plugin\EntityReferenceSelection\TestSelection
+   */
+  protected $selectionHandler;
+
+  /**
+   * Test block expectations.
+   *
+   * @var array
+   */
+  protected $expectations;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->installSchema('system', ['sequence']);
+    $this->installSchema('system', ['sequences']);
+    $this->installEntitySchema('user');
+    $this->installEntitySchema('block_content');
+
+    // Create a block content type.
+    $block_content_type = BlockContentType::create([
+      'id' => 'spiffy',
+      'label' => 'Mucho spiffy',
+      'description' => "Provides a block type that increases your site's spiffiness by up to 11%",
+    ]);
+    $block_content_type->save();
+    $this->entityTypeManager = $this->container->get('entity_type.manager');
+
+    // And reusable block content entities.
+    $this->blockReusable = BlockContent::create([
+      'info' => 'Reusable Block',
+      'type' => 'spiffy',
+    ]);
+    $this->blockReusable->save();
+    $this->blockNonReusable = BlockContent::create([
+      'info' => 'Non-reusable Block',
+      'type' => 'spiffy',
+      'reusable' => FALSE,
+    ]);
+    $this->blockNonReusable->save();
+
+    $configuration = [
+      'target_type' => 'block_content',
+      'target_bundles' => ['spiffy' => 'spiffy'],
+      'sort' => ['field' => '_none'],
+    ];
+    $this->selectionHandler = new TestSelection($configuration, '', '', $this->container->get('entity.manager'), $this->container->get('module_handler'), \Drupal::currentUser());
+
+    // Setup the 3 expectation cases.
+    $this->expectations = [
+      'both_blocks' => [
+        'spiffy' => [
+          $this->blockReusable->id() => $this->blockReusable->label(),
+          $this->blockNonReusable->id() => $this->blockNonReusable->label(),
+        ],
+      ],
+      'block_reusable' => ['spiffy' => [$this->blockReusable->id() => $this->blockReusable->label()]],
+      'block_non_reusable' => ['spiffy' => [$this->blockNonReusable->id() => $this->blockNonReusable->label()]],
+    ];
+  }
+
+  /**
+   * Tests to make sure queries without the expected tags are not altered.
+   *
+   * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
+   * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
+   */
+  public function testQueriesNotAltered() {
+    // Ensure that queries without all the tags are not altered.
+    $query = $this->entityTypeManager->getStorage('block_content')->getQuery();
+    $this->assertCount(2, $query->execute());
+
+    $query = $this->entityTypeManager->getStorage('block_content')->getQuery();
+    $query->addTag('block_content_access');
+    $this->assertCount(2, $query->execute());
+
+    $query = $this->entityTypeManager->getStorage('block_content')->getQuery();
+    $query->addTag('entity_query_block_content');
+    $this->assertCount(2, $query->execute());
+  }
+
+  /**
+   * Test with no conditions set.
+   *
+   * @throws \Drupal\Core\Entity\EntityStorageException
+   */
+  public function testNoConditions() {
+    $this->assertEquals(
+      $this->expectations['block_reusable'],
+      $this->selectionHandler->getReferenceableEntities()
+    );
+
+    $this->blockNonReusable->setReusable();
+    $this->blockNonReusable->save();
+
+    // Ensure that the block is now returned as a referenceable entity.
+    $this->assertEquals(
+      $this->expectations['both_blocks'],
+      $this->selectionHandler->getReferenceableEntities()
+    );
+  }
+
+  /**
+   * Tests setting 'reusable' condition on different levels.
+   *
+   * @dataProvider fieldConditionProvider
+   *
+   * @throws \Exception
+   */
+  public function testFieldConditions($condition_type, $is_reusable) {
+    $this->selectionHandler->setTestMode($condition_type, $is_reusable);
+    $this->assertEquals(
+      $is_reusable ? $this->expectations['block_reusable'] : $this->expectations['block_non_reusable'],
+      $this->selectionHandler->getReferenceableEntities()
+    );
+  }
+
+  /**
+   * Provides possible fields and condition types.
+   */
+  public function fieldConditionProvider() {
+    $cases = [];
+    foreach (['base', 'group', 'nested_group'] as $condition_type) {
+      foreach ([TRUE, FALSE] as $reusable) {
+        $cases["$condition_type:" . ($reusable ? 'reusable' : 'non-reusable')] = [
+          $condition_type,
+          $reusable,
+        ];
+      }
+    }
+    return $cases;
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Unit/Access/AccessGroupAndTest.php b/core/modules/block_content/tests/src/Unit/Access/AccessGroupAndTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..8915674862383c3a80398cdc9a2f5477ca826624
--- /dev/null
+++ b/core/modules/block_content/tests/src/Unit/Access/AccessGroupAndTest.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace Drupal\Tests\block_content\Unit\Access;
+
+use Drupal\block_content\Access\AccessGroupAnd;
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests accessible groups.
+ *
+ * @group block_content
+ */
+class AccessGroupAndTest extends UnitTestCase {
+
+  use AccessibleTestingTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->account = $this->prophesize(AccountInterface::class)->reveal();
+  }
+
+  /**
+   * @covers \Drupal\block_content\Access\AccessGroupAnd
+   */
+  public function testGroups() {
+    $allowedAccessible = $this->createAccessibleDouble(AccessResult::allowed());
+    $forbiddenAccessible = $this->createAccessibleDouble(AccessResult::forbidden());
+    $neutralAccessible = $this->createAccessibleDouble(AccessResult::neutral());
+
+    // Ensure that groups with no dependencies return a neutral access result.
+    $this->assertTrue((new AccessGroupAnd())->access('view', $this->account, TRUE)->isNeutral());
+
+    $andNeutral = new AccessGroupAnd();
+    $andNeutral->addDependency($allowedAccessible)->addDependency($neutralAccessible);
+    $this->assertTrue($andNeutral->access('view', $this->account, TRUE)->isNeutral());
+
+    $andForbidden = $andNeutral;
+    $andForbidden->addDependency($forbiddenAccessible);
+    $this->assertTrue($andForbidden->access('view', $this->account, TRUE)->isForbidden());
+
+    // Ensure that groups added to other groups works.
+    $andGroupsForbidden = new AccessGroupAnd();
+    $andGroupsForbidden->addDependency($andNeutral)->addDependency($andForbidden);
+    $this->assertTrue($andGroupsForbidden->access('view', $this->account, TRUE)->isForbidden());
+    // Ensure you can add a non-group accessible object.
+    $andGroupsForbidden->addDependency($allowedAccessible);
+    $this->assertTrue($andGroupsForbidden->access('view', $this->account, TRUE)->isForbidden());
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Unit/Access/AccessibleTestingTrait.php b/core/modules/block_content/tests/src/Unit/Access/AccessibleTestingTrait.php
new file mode 100644
index 0000000000000000000000000000000000000000..8aab22782b05a9f1ed7a2af99ba5db6e862216f8
--- /dev/null
+++ b/core/modules/block_content/tests/src/Unit/Access/AccessibleTestingTrait.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Drupal\Tests\block_content\Unit\Access;
+
+use Drupal\Core\Access\AccessibleInterface;
+use Drupal\Core\Access\AccessResultInterface;
+
+/**
+ * Helper methods testing accessible interfaces.
+ */
+trait AccessibleTestingTrait {
+
+  /**
+   * The test account.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $account;
+
+  /**
+   * Creates AccessibleInterface object from access result object for testing.
+   *
+   * @param \Drupal\Core\Access\AccessResultInterface $accessResult
+   *   The accessible result to return.
+   *
+   * @return \Drupal\Core\Access\AccessibleInterface
+   *   The AccessibleInterface object.
+   */
+  private function createAccessibleDouble(AccessResultInterface $accessResult) {
+    $accessible = $this->prophesize(AccessibleInterface::class);
+    $accessible->access('view', $this->account, TRUE)
+      ->willReturn($accessResult);
+    return $accessible->reveal();
+  }
+
+}
diff --git a/core/modules/block_content/tests/src/Unit/Access/DependentAccessTest.php b/core/modules/block_content/tests/src/Unit/Access/DependentAccessTest.php
new file mode 100644
index 0000000000000000000000000000000000000000..2be368601d7e0d637328567dc421de3a12ea11f4
--- /dev/null
+++ b/core/modules/block_content/tests/src/Unit/Access/DependentAccessTest.php
@@ -0,0 +1,160 @@
+<?php
+
+namespace Drupal\Tests\block_content\Unit\Access;
+
+use Drupal\block_content\Access\AccessGroupAnd;
+use Drupal\Core\Access\AccessResult;
+use Drupal\block_content\Access\RefinableDependentAccessInterface;
+use Drupal\block_content\Access\RefinableDependentAccessTrait;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass  \Drupal\block_content\Access\RefinableDependentAccessTrait
+ *
+ * @group block_content
+ */
+class DependentAccessTest extends UnitTestCase {
+  use AccessibleTestingTrait;
+
+  /**
+   * An accessible object that results in forbidden access result.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface
+   */
+  protected $forbidden;
+
+  /**
+   * An accessible object that results in neutral access result.
+   *
+   * @var \Drupal\Core\Access\AccessibleInterface
+   */
+  protected $neutral;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->account = $this->prophesize(AccountInterface::class)->reveal();
+    $this->forbidden = $this->createAccessibleDouble(AccessResult::forbidden('Because I said so'));
+    $this->neutral = $this->createAccessibleDouble(AccessResult::neutral('I have no opinion'));
+  }
+
+  /**
+   * Test that the previous dependency is replaced when using set.
+   *
+   * @covers ::setAccessDependency
+   *
+   * @dataProvider providerTestSetFirst
+   */
+  public function testSetAccessDependency($use_set_first) {
+    $testRefinable = new RefinableDependentAccessTraitTestClass();
+
+    if ($use_set_first) {
+      $testRefinable->setAccessDependency($this->forbidden);
+    }
+    else {
+      $testRefinable->addAccessDependency($this->forbidden);
+    }
+    $accessResult = $testRefinable->getAccessDependency()->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResult->isForbidden());
+    $this->assertEquals('Because I said so', $accessResult->getReason());
+
+    // Calling setAccessDependency() replaces the existing dependency.
+    $testRefinable->setAccessDependency($this->neutral);
+    $dependency = $testRefinable->getAccessDependency();
+    $this->assertFalse($dependency instanceof AccessGroupAnd);
+    $accessResult = $dependency->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResult->isNeutral());
+    $this->assertEquals('I have no opinion', $accessResult->getReason());
+  }
+
+  /**
+   * Tests merging a new dependency with existing non-group access dependency.
+   *
+   * @dataProvider providerTestSetFirst
+   */
+  public function testMergeNonGroup($use_set_first) {
+    $testRefinable = new RefinableDependentAccessTraitTestClass();
+    if ($use_set_first) {
+      $testRefinable->setAccessDependency($this->forbidden);
+    }
+    else {
+      $testRefinable->addAccessDependency($this->forbidden);
+    }
+
+    $accessResult = $testRefinable->getAccessDependency()->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResult->isForbidden());
+    $this->assertEquals('Because I said so', $accessResult->getReason());
+
+    $testRefinable->addAccessDependency($this->neutral);
+    /** @var \Drupal\block_content\Access\AccessGroupAnd $dependency */
+    $dependency = $testRefinable->getAccessDependency();
+    // Ensure the new dependency create a new AND group when merged.
+    $this->assertTrue($dependency instanceof AccessGroupAnd);
+    $dependencies = $dependency->getDependencies();
+    $accessResultForbidden = $dependencies[0]->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResultForbidden->isForbidden());
+    $this->assertEquals('Because I said so', $accessResultForbidden->getReason());
+    $accessResultNeutral = $dependencies[1]->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResultNeutral->isNeutral());
+    $this->assertEquals('I have no opinion', $accessResultNeutral->getReason());
+
+  }
+
+  /**
+   * Tests merging a new dependency with an existing access group dependency.
+   *
+   * @dataProvider providerTestSetFirst
+   */
+  public function testMergeGroup($use_set_first) {
+    $andGroup = new AccessGroupAnd();
+    $andGroup->addDependency($this->forbidden);
+    $testRefinable = new RefinableDependentAccessTraitTestClass();
+    if ($use_set_first) {
+      $testRefinable->setAccessDependency($andGroup);
+    }
+    else {
+      $testRefinable->addAccessDependency($andGroup);
+    }
+
+    $testRefinable->addAccessDependency($this->neutral);
+    /** @var \Drupal\block_content\Access\AccessGroupAnd $dependency */
+    $dependency = $testRefinable->getAccessDependency();
+
+    // Ensure the new dependency is merged with the existing group.
+    $this->assertTrue($dependency instanceof AccessGroupAnd);
+    $dependencies = $dependency->getDependencies();
+    $accessResultForbidden = $dependencies[0]->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResultForbidden->isForbidden());
+    $this->assertEquals('Because I said so', $accessResultForbidden->getReason());
+    $accessResultNeutral = $dependencies[1]->access('view', $this->account, TRUE);
+    $this->assertTrue($accessResultNeutral->isNeutral());
+    $this->assertEquals('I have no opinion', $accessResultNeutral->getReason());
+  }
+
+  /**
+   * Dataprovider for all test methods.
+   *
+   * Provides test cases for calling setAccessDependency() or
+   * mergeAccessDependency() first. A call to either should behave the same on a
+   * new RefinableDependentAccessInterface object.
+   */
+  public function providerTestSetFirst() {
+    return [
+      [TRUE],
+      [FALSE],
+    ];
+  }
+
+}
+
+/**
+ * Test class that implements RefinableDependentAccessInterface.
+ */
+class RefinableDependentAccessTraitTestClass implements RefinableDependentAccessInterface {
+
+  use RefinableDependentAccessTrait;
+
+}