diff --git a/templates/index.html b/templates/index.html
index d3059dd..a934117 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -6,7 +6,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>YAPF Online Demo</title>
 
-    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.0/css/bootstrap.min.css" integrity="sha384-PmY9l28YgO4JwMKbTvgaS7XNZJ30MK9FAZjjzXtlqyZCqBY6X6bXIkM++IkyinN+" crossorigin="anonymous">
+    <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-PmY9l28YgO4JwMKbTvgaS7XNZJ30MK9FAZjjzXtlqyZCqBY6X6bXIkM++IkyinN+" crossorigin="anonymous">
 
     <!--[if lt IE 9]>
       <script src="https://cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.3/html5shiv.min.js" integrity="sha256-3Jy/GbSLrg0o9y5Z5n1uw0qxZECH7C6OQpVBgNFYa0g=" crossorigin="anonymous"></script>
@@ -122,8 +122,8 @@ <h1>YAPF Online Demo</h1>
       </div>
     </div>
 
-    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.4/jquery.min.js" integrity="sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ+Xp8a4MxAQ=" crossorigin="anonymous"></script>
-    <script src="https://stackpath.bootstrapcdn.com/bootstrap/3.4.0/js/bootstrap.min.js" integrity="sha384-vhJnz1OVIdLktyixHY4Uk3OHEwdQqPppqYR8+5mjsauETgLOcEynD9oPHhhz18Nw" crossorigin="anonymous"></script>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js" integrity="sha256-ZosEbRLbNQzLpnKIkEdrPv7lOy9C27hHQ+Xp8a4MxAQ=" crossorigin="anonymous"></script>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.2.1/js/bootstrap.min.js" integrity="sha384-vhJnz1OVIdLktyixHY4Uk3OHEwdQqPppqYR8+5mjsauETgLOcEynD9oPHhhz18Nw" crossorigin="anonymous"></script>
     <script src="https://cdnjs.cloudflare.com/ajax/libs/ace/1.4.2/ace.js" integrity="sha256-rfN9xU0ELcvTsc3WUaKlvSVEfzLvFCyl+ID09aieASo=" crossorigin="anonymous"></script>
     <script>
       $(document).ready(function() {