diff --git a/doc/t2h.pm b/doc/t2h.pm
index 7f771f996a..ca778422fa 100644
--- a/doc/t2h.pm
+++ b/doc/t2h.pm
@@ -169,6 +169,7 @@ EOT
 
     my $head2 = $ENV{"FFMPEG_HEADER2"} || <<EOT;
     </title>
+    <meta name="viewport" content="width=device-width,initial-scale=1.0">
     <link rel="stylesheet" type="text/css" href="bootstrap.min.css">
     <link rel="stylesheet" type="text/css" href="style.min.css">
   </head>