diff --git a/resources/celerity/map.php b/resources/celerity/map.php
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -9,7 +9,7 @@
   'names' => array(
     'conpherence.pkg.css' => '79a197f6',
     'conpherence.pkg.js' => '020aebcf',
-    'core.pkg.css' => '578670e1',
+    'core.pkg.css' => 'afa42e73',
     'core.pkg.js' => '086da722',
     'dark-console.pkg.js' => '187792c2',
     'differential.pkg.css' => 'db7c5008',
@@ -104,7 +104,7 @@
     'rsrc/css/application/tokens/tokens.css' => 'ce5a50bd',
     'rsrc/css/application/uiexample/example.css' => '549e220b',
     'rsrc/css/core/core.css' => '83d97073',
-    'rsrc/css/core/remarkup.css' => '90b42b95',
+    'rsrc/css/core/remarkup.css' => '46a6b5c6',
     'rsrc/css/core/syntax.css' => '548567f6',
     'rsrc/css/core/z-index.css' => '56fbe5ba',
     'rsrc/css/diviner/diviner-shared.css' => '4bd263b0',
@@ -774,7 +774,7 @@
     'phabricator-object-selector-css' => 'ee77366f',
     'phabricator-phtize' => '2f1db1ed',
     'phabricator-prefab' => '5793d835',
-    'phabricator-remarkup-css' => '90b42b95',
+    'phabricator-remarkup-css' => '46a6b5c6',
     'phabricator-remarkup-metadata' => 'e40c4991',
     'phabricator-search-results-css' => '9ea70ace',
     'phabricator-shaped-request' => '995f5102',
diff --git a/src/applications/files/markup/PhabricatorEmbedFileRemarkupRule.php b/src/applications/files/markup/PhabricatorEmbedFileRemarkupRule.php
--- a/src/applications/files/markup/PhabricatorEmbedFileRemarkupRule.php
+++ b/src/applications/files/markup/PhabricatorEmbedFileRemarkupRule.php
@@ -311,6 +311,11 @@
       $mime_type = $file->getMimeType();
     }
 
+    $thumb_class = null;
+    if (isset($options['size']) && $options['size'] == 'thumb') {
+      $thumb_class = ' video-thumb';
+    }
+
     return $this->newTag(
       $tag,
       array(
@@ -319,7 +324,7 @@
         'autoplay' => $autoplay,
         'loop' => idx($options, 'loop') ? 'loop' : null,
         'alt' => $options['alt'],
-        'class' => 'phabricator-media',
+        'class' => 'phabricator-media'.$thumb_class,
       ),
       $this->newTag(
         'source',
diff --git a/webroot/rsrc/css/core/remarkup.css b/webroot/rsrc/css/core/remarkup.css
--- a/webroot/rsrc/css/core/remarkup.css
+++ b/webroot/rsrc/css/core/remarkup.css
@@ -263,6 +263,12 @@
   max-width: 95%;
 }
 
+.phabricator-remarkup video.video-thumb {
+  display: inline-block;
+  margin: 0 auto;
+  max-width: 400px;
+}
+
 .phabricator-remarkup-mention-exists {
   font-weight: bold;
   background: #e6f3ff;