diff --git a/js/index.js b/js/index.js
index 81c7b6b..d03fe41 100644
--- a/js/index.js
+++ b/js/index.js
@@ -255,7 +255,8 @@ validatePurpose(document.querySelector("#purpose input"));
 // generate qr code on first visit
 regenerate();
 
-if ("serviceWorker" in navigator) {
-  navigator.serviceWorker.register("/js/service-worker.js");
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.register('/sw.js')
+    .catch(err => console.error('Service Worker registration failed:', err));
 }
 
diff --git a/js/service-worker.js b/js/service-worker.js
index 17e183c..35ad423 100644
--- a/js/service-worker.js
+++ b/js/service-worker.js
@@ -20,7 +20,28 @@ self.addEventListener("install", (event) => {
 });
 */
 
-self.addEventListener("fetch", event => {
-  event.respondWith(fetch(event.request));
+self.addEventListener('install', event => {
+  event.waitUntil(
+    caches.open('bezahlbrudi-cache-v1').then(cache => {
+      return cache.addAll([
+        '/',
+        '/index.html',
+        '/css/bulma.min.css',
+        '/js/index.js',
+        '/js/qr-creator.min.js',
+        '/img/icon-192.png',
+        '/img/icon-512.png'
+        // add any other core assets here
+      ]);
+    })
+  );
+});
+
+self.addEventListener('fetch', event => {
+  event.respondWith(
+    caches.match(event.request).then(cached => {
+      return cached || fetch(event.request);
+    })
+  );
 });