diff --git a/sw-test.js b/sw-test.js
new file mode 100644
index 00000000..5fa57487
--- /dev/null
+++ b/sw-test.js
@@ -0,0 +1,76 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+        http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+const VERSION = "foo3";
+const OFFLINE_FILES = ["hydrogen-129215894.js","hydrogen-1625084908.css","index.html","themes/element/bundle-1000196323.css","themes/bubbles/bundle-2682099160.css","icon-2793984973.png","icon-maskable-317721575.png"];
+// TODO: cache these files when requested
+// The difficulty is that these are relative filenames, and we don't have access to document.baseURI
+// Clients.match({type: "window"}).url and assume they are all the same? they really should be ... safari doesn't support this though
+const CACHE_FILES = ["themes/element/element-logo-2959259787.svg","themes/element/icons/chevron-right-787082136.svg","themes/element/icons/send-4065347741.svg","themes/element/inter/Inter-Black-276207522.woff","themes/element/inter/Inter-BlackItalic-3159247813.woff","themes/element/inter/Inter-Bold-4187626158.woff","themes/element/inter/Inter-BoldItalic-641187949.woff","themes/element/inter/Inter-ExtraBold-3888913940.woff","themes/element/inter/Inter-ExtraBoldItalic-2880676406.woff","themes/element/inter/Inter-ExtraLight-3277895962.woff","themes/element/inter/Inter-ExtraLightItalic-3022762143.woff","themes/element/inter/Inter-Italic-4024721388.woff","themes/element/inter/Inter-Light-3990448997.woff","themes/element/inter/Inter-LightItalic-412813693.woff","themes/element/inter/Inter-Medium-2285329551.woff","themes/element/inter/Inter-MediumItalic-1722521156.woff","themes/element/inter/Inter-Regular-2779214592.woff","themes/element/inter/Inter-SemiBold-1906312195.woff","themes/element/inter/Inter-SemiBoldItalic-3778207334.woff","themes/element/inter/Inter-Thin-1593561269.woff","themes/element/inter/Inter-ThinItalic-1888295987.woff"];
+const cacheName = `hydrogen-${VERSION}`;
+
+self.addEventListener('install', function(e) {
+    console.log("installing service worker", VERSION);
+    e.waitUntil(
+        caches.open(cacheName).then(function(cache) {
+            return cache.addAll(OFFLINE_FILES);
+        })
+    );
+});
+
+self.addEventListener('activate', (event) => {
+    console.log("activating service worker", VERSION);
+    event.waitUntil(
+        caches.keys().then((keyList) => {
+            return Promise.all(keyList.map((key) => {
+                if (key !== cacheName) {
+                    return caches.delete(key);
+                }
+            }));
+        })
+    );
+});
+
+self.addEventListener('fetch', (event) => {
+    console.log("new fetch event in sw", event.request.headers);
+    event.respondWith(
+        caches.open(cacheName)
+            .then(cache => cache.match(event.request))
+            .then((response) => response || fetch(event.request))
+    );
+});
+
+// service-worker.js
+// Listen to the request
+self.addEventListener('message', (event) => {
+  if (event.data && event.data.type === 'PING') {
+    // Select who we want to respond to
+    self.clients.matchAll({
+      includeUncontrolled: true,
+      type: 'window',
+    }).then((clients) => {
+      if (clients && clients.length) {
+        // Send a response - the clients
+        // array is ordered by last focused
+        clients[0].postMessage({
+          type: 'PONG',
+          files: OFFLINE_FILES,
+          version: VERSION,
+        });
+      }
+    });
+  }
+});