Video formats are not limited to webm

boards/models/attachment/viewers.py

@@ -3,7 +3,10 b' from django.contrib.staticfiles.template'
 
 FILE_STUB_IMAGE = 'images/file.png'
 
-FILE_TYPE_WEBM = 'webm'
+FILE_TYPES_VIDEO = (
+    'webm',
+    'mp4',
+)
 FILE_TYPE_SVG = 'svg'
 FILE_TYPES_AUDIO = (
     'ogg',
@@ -37,10 +40,10 b' class AbstractViewer:'
                '</a>'.format(self.file.url,static(FILE_STUB_IMAGE))
 
 
-class WebmViewer(AbstractViewer):
+class VideoViewer(AbstractViewer):
     @staticmethod
     def supports(file_type):
-        return file_type == FILE_TYPE_WEBM
+        return file_type in FILE_TYPES_VIDEO
 
     def get_format_view(self):
         return '<video width="200" height="150" controls src="{}"></video>'\