diff --git a/prototypes/olmtest-ie11.html b/prototypes/olmtest-ie11.html
index 316f5423..dec102ff 100644
--- a/prototypes/olmtest-ie11.html
+++ b/prototypes/olmtest-ie11.html
@@ -41,45 +41,79 @@
     <script src="https://cdn.jsdelivr.net/npm/promise-polyfill@8/dist/polyfill.min.js"></script>
     <script type="text/javascript" src="../lib/olm/olm_legacy.js"></script>
     <script type="text/javascript">
-        function main() {
-            if (window.msCrypto && !window.crypto) {
-                window.crypto = window.msCrypto;
-            }
-            Olm.init(   ).then(function() {
-                const alice = new Olm.Account();
+        function doit(log) {           
+                var alice = new Olm.Account();
                 alice.create();
-                console.log("alice", alice.identity_keys());
+                log("alice", alice.identity_keys());
 
-                const bob = new Olm.Account();
+                var bob = new Olm.Account();
                 bob.unpickle("secret", "EWfA87or4GgQ+wqVkyuFiW9gUk3FI6QSXgp8E2dS5RFLvXgy4oFvxwQ1gVnbMkdJz2Hy9ex9UmJ/ZyuRU0aRt0IwXpw/SUNq4IQeVJ7J/miXW7rV4Ep+4RSEf945KbDrokDCS2CoL5PIfv/NYyey32gA0hMi8wWIfIlOxFBV4SBJYSC+Qd54VjprwCg0Sn9vjQouKVrM/+5jzsv9+JK5OpWW0Vrb3qrXwyAOEAQ4WlOQcqZHAyPQIw");
-                console.log("bob", bob.identity_keys());
+                log("bob", bob.identity_keys());
                 // generate OTK on receiver side
                 bob.generate_one_time_keys(1);
-                const bobOneTimeKeys = JSON.parse(bob.one_time_keys());
-                const otkName = Object.getOwnPropertyNames(bobOneTimeKeys.curve25519)[0];
-                const bobOneTimeKey = bobOneTimeKeys.curve25519[otkName];
+                var bobOneTimeKeys = JSON.parse(bob.one_time_keys());
+                var otkName = Object.getOwnPropertyNames(bobOneTimeKeys.curve25519)[0];
+                var bobOneTimeKey = bobOneTimeKeys.curve25519[otkName];
                 // encrypt
-                const aliceSession = new Olm.Session();
+                var aliceSession = new Olm.Session();
                 aliceSession.create_outbound(
                     alice,
                     JSON.parse(bob.identity_keys()).curve25519,
                     bobOneTimeKey
                 );
-                const message = aliceSession.encrypt("hello secret world");
-                console.log("message", message);
+                var message = aliceSession.encrypt("hello secret world");
+                log("message", message);
                 // decrypt
-                const bobSession = new Olm.Session();
+                var bobSession = new Olm.Session();
                 bobSession.create_inbound(bob, message.body);
-                const plaintext = bobSession.decrypt(message.type, message.body);
-                console.log("plaintext", plaintext);
+                var plaintext = bobSession.decrypt(message.type, message.body);
+                log("plaintext", plaintext);
                 // remove Bob's OTK as it was used to start an olm session
-                console.log("bob OTK before removing", bob.one_time_keys());
+                log("bob OTK before removing", bob.one_time_keys());
                 bob.remove_one_time_keys(bobSession);
-                console.log("bob OTK after removing", bob.one_time_keys());
+                log("bob OTK after removing", bob.one_time_keys());
+        }
+
+        if (window.msCrypto && !window.crypto) {
+            window.crypto = window.msCrypto;
+        }
+
+        function doRun(e) {
+            e.target.setAttribute("disabled", "disabled");
+            var logEl = document.getElementById("log");
+            logEl.innerText = "";
+            var startTime = performance.now();
+            function log() {
+                var timeDiff = Math.round(performance.now() - startTime).toString();
+                while (timeDiff.length < 5) {
+                    timeDiff = "0" + timeDiff;
+                }
+                logEl.appendChild(document.createTextNode(timeDiff + " "));
+                for (var i = 0; i <  arguments.length; i += 1) {
+                    var value = arguments[i];
+                    if (typeof value !== "string") {
+                        value = JSON.stringify(value);
+                    }
+                    logEl.appendChild(document.createTextNode(value + " "));
+                }
+                logEl.appendChild(document.createTextNode("\n"));
+            }
+            doit(log);
+            e.target.removeAttribute("disabled");
+        }
+
+        function main() {
+             Olm.init(   ).then(function() {
+                var startButton = document.getElementById("start");
+                startButton.innerText = "Start";
+                startButton.addEventListener("click", doRun);
             });
         }
+        document.addEventListener("DOMContentLoaded", main);
         main();
     </script>
+    <pre id="log"></pre>
+    <button id="start">Loading...</button>
 </body>
 </html>