diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index 5db5442746d570b86670eb655d239c6b0e06250c..aef62094afa18944b685398392780e81c423f0f2 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -1050,6 +1050,10 @@ function comment_build_content(Comment $comment, Node $node, $view_mode = 'full'
   // Remove previously built content, if exists.
   $comment->content = array();
 
+  // Allow modules to change the view mode.
+  $context = array('langcode' => $langcode);
+  drupal_alter('entity_view_mode', $view_mode, $comment, $context);
+
   // Build fields content.
   field_attach_prepare_view('comment', array($comment->cid => $comment), $view_mode, $langcode);
   entity_prepare_view('comment', array($comment->cid => $comment), $langcode);
diff --git a/core/modules/entity/entity.api.php b/core/modules/entity/entity.api.php
index 98e32b842365049776a4bb857fef8edce4ac28fc..bd5d1477fcb10cc162e4e64664511e4beadead5f 100644
--- a/core/modules/entity/entity.api.php
+++ b/core/modules/entity/entity.api.php
@@ -448,3 +448,21 @@ function hook_entity_prepare_view($entities, $entity_type) {
     }
   }
 }
+
+/**
+ * Change the view mode of an entity that is being displayed.
+ *
+ * @param string $view_mode
+ *   The view_mode that is to be used to display the entity.
+ * @param Drupal\entity\EntityInterface $entity
+ *   The entity that is being viewed.
+ * @param array $context
+ *   Array with additional context information, currently only contains the
+ *   langcode the entity is viewed in.
+ */
+function hook_entity_view_mode_alter(&$view_mode, Drupal\entity\EntityInterface $entity, $context) {
+  // For nodes, change the view mode when it is teaser.
+  if ($entity->entityType() == 'node' && $view_mode == 'teaser') {
+    $view_mode = 'my_custom_view_mode';
+  }
+}
diff --git a/core/modules/node/node.module b/core/modules/node/node.module
index 1b0d670f5ea1c8da05f50ba5567667968985c10c..349aab53f4af458de0146e998ef150ea275ed68b 100644
--- a/core/modules/node/node.module
+++ b/core/modules/node/node.module
@@ -1202,6 +1202,10 @@ function node_build_content(Node $node, $view_mode = 'full', $langcode = NULL) {
   // Remove previously built content, if exists.
   $node->content = array();
 
+  // Allow modules to change the view mode.
+  $context = array('langcode' => $langcode);
+  drupal_alter('entity_view_mode', $view_mode, $node, $context);
+
   // The 'view' hook can be implemented to overwrite the default function
   // to display nodes.
   if (node_hook($node, 'view')) {
diff --git a/core/modules/node/tests/modules/node_test/node_test.module b/core/modules/node/tests/modules/node_test/node_test.module
index f541d10832eab28ab0a52d0caa156b5ccaaa628c..bfad466649e4d4729ef49c818ae03407c5a5630c 100644
--- a/core/modules/node/tests/modules/node_test/node_test.module
+++ b/core/modules/node/tests/modules/node_test/node_test.module
@@ -151,3 +151,13 @@ function node_test_node_update(Node $node) {
     }
   }
 }
+
+/**
+ * Implements hook_entity_view_mode_alter().
+ */
+function node_test_entity_view_mode_alter(&$view_mode, Drupal\entity\EntityInterface $entity, $context) {
+  // Only alter the view mode if we are on the test callback.
+  if ($change_view_mode = variable_get('node_test_change_view_mode', '')) {
+    $view_mode = $change_view_mode;
+  }
+}
diff --git a/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
index a37da8aed9a51b359a17fcc9a340733c88255023..a772e0259be4a3d410a46958bc178e9694f1ae49 100644
--- a/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -587,6 +587,10 @@ function taxonomy_term_view(Term $term, $view_mode = 'full', $langcode = NULL) {
     $langcode = language(LANGUAGE_TYPE_CONTENT)->langcode;
   }
 
+  // Allow modules to change the view mode.
+  $context = array('langcode' => $langcode);
+  drupal_alter('entity_view_mode', $view_mode, $term, $context);
+
   field_attach_prepare_view('taxonomy_term', array($term->tid => $term), $view_mode, $langcode);
   entity_prepare_view('taxonomy_term', array($term->tid => $term), $langcode);
 
diff --git a/core/modules/user/user.module b/core/modules/user/user.module
index 4217234368442471f46ec4ac5c0e19d44e22230a..44cb2664e1b19da00f6141cd1a140603fe7ac549 100644
--- a/core/modules/user/user.module
+++ b/core/modules/user/user.module
@@ -2115,6 +2115,10 @@ function user_build_content($account, $view_mode = 'full', $langcode = NULL) {
   // Remove previously built content, if exists.
   $account->content = array();
 
+  // Allow modules to change the view mode.
+  $context = array('langcode' => $langcode);
+  drupal_alter('entity_view_mode', $view_mode, $account, $context);
+
   // Build fields content.
   field_attach_prepare_view('user', array($account->uid => $account), $view_mode, $langcode);
   entity_prepare_view('user', array($account->uid => $account), $langcode);