diff --git a/trac/templates/layout.html b/trac/templates/layout.html
index da39ceef2e..a6e92d2983 100644
--- a/trac/templates/layout.html
+++ b/trac/templates/layout.html
@@ -24,6 +24,7 @@
     #   if chrome.content_type == 'text/html':
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
     <meta http-equiv="X-UA-Compatible" content="IE=edge" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
     #   endif
 
     #   for meta in chrome.metas: