diff --git a/app.js b/app.js
index a5e0634..114a9b3 100644
--- a/app.js
+++ b/app.js
@@ -2,7 +2,7 @@
   'use strict';
 
   // ==================== CONFIG ====================
-  var BUILD = '10';                    // bump every deploy — shown on Debug screen to confirm version
+  var BUILD = '11';                    // bump every deploy — shown on Debug screen to confirm version
   var STORAGE_KEY = 'stepview_v1';
   var RING_CIRC = 603;                 // 2*pi*r, r=96
   var KCAL_PER_KG_PER_KM = 0.9;        // gross walking estimate
@@ -313,6 +313,7 @@
       case 'weight-dec': state.settings.weightKg = clampWeight(state.settings.weightKg - 1); afterSetting(); break;
       case 'height-inc': state.settings.heightCm = clampHeight(state.settings.heightCm + 1); afterSetting(); break;
       case 'height-dec': state.settings.heightCm = clampHeight(state.settings.heightCm - 1); afterSetting(); break;
+      case 'update-refresh': if (waitingWorker) waitingWorker.postMessage('skipWaiting'); break;
     }
   }
   function afterSetting() { renderSettings(); render(); save(); }
@@ -437,10 +438,40 @@
     };
   }
 
+  // ==================== SERVICE WORKER ====================
+  var waitingWorker = null;
+  function setupSW() {
+    if (!('serviceWorker' in navigator)) return;
+    navigator.serviceWorker.register('sw.js').then(function (reg) {
+      if (reg.waiting) {
+        waitingWorker = reg.waiting;
+        showUpdateBanner();
+      }
+      reg.addEventListener('updatefound', function () {
+        var newWorker = reg.installing;
+        newWorker.addEventListener('statechange', function () {
+          if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
+            waitingWorker = newWorker;
+            showUpdateBanner();
+          }
+        });
+      });
+    });
+    navigator.serviceWorker.addEventListener('controllerchange', function () {
+      window.location.reload();
+    });
+  }
+
+  function showUpdateBanner() {
+    var banner = $('update-banner');
+    if (banner) banner.classList.remove('hidden');
+  }
+
   // ==================== INIT ====================
   function init() {
     document.querySelectorAll('.screen').forEach(function (s) { if (s.id) screens[s.id] = s; });
     load();
+    setupSW();
     setupEvents();
     setupMotion();        // always-on accelerometer capture (independent of the UI)
     render();
diff --git a/index.html b/index.html
index 84c693c..e64602d 100644
--- a/index.html
+++ b/index.html
@@ -7,7 +7,8 @@
   <meta name="mrbd-web-app-capable" content="yes">
   <title>StepView — Step, Distance & Calorie Counter</title>
   <link rel="icon" href="favicon.svg" type="image/svg+xml">
-  <link rel="stylesheet" href="styles.css?v=10">
+  <link rel="manifest" href="manifest.json">
+  <link rel="stylesheet" href="styles.css?v=11">
 </head>
 <body>
   <div id="app">
@@ -132,6 +133,9 @@ <h1>Debug</h1>
       </nav>
     </div>
   </div>
-  <script src="app.js?v=10"></script>
+  <script src="app.js?v=11"></script>
+  <div id="update-banner" class="update-banner hidden" data-action="update-refresh">
+    New version available! <span>Tap to update</span>
+  </div>
 </body>
 </html>
diff --git a/manifest.json b/manifest.json
new file mode 100644
index 0000000..472a737
--- /dev/null
+++ b/manifest.json
@@ -0,0 +1,16 @@
+{
+  "name": "StepView",
+  "short_name": "StepView",
+  "description": "Step, distance, and calorie counter for Meta Ray-Ban Display glasses.",
+  "start_url": "./index.html",
+  "display": "standalone",
+  "background_color": "#000000",
+  "theme_color": "#000000",
+  "icons": [
+    {
+      "src": "favicon.svg",
+      "sizes": "any",
+      "type": "image/svg+xml"
+    }
+  ]
+}
diff --git a/styles.css b/styles.css
index f3f2519..c2cddaf 100644
--- a/styles.css
+++ b/styles.css
@@ -234,4 +234,25 @@ html, body {
 }
 .toast.show { transform: translateX(-50%) translateY(0); opacity: 1; }
 
+/* --- Update Banner --- */
+.update-banner {
+  position: absolute;
+  bottom: 22px;
+  left: 50%;
+  transform: translateX(-50%);
+  background: var(--surface);
+  border: 2px solid var(--green);
+  border-radius: 16px;
+  padding: 14px 24px;
+  font-size: 19px;
+  font-weight: 700;
+  color: #fff;
+  z-index: 100;
+  cursor: pointer;
+  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.5);
+  white-space: nowrap;
+}
+.update-banner span { color: var(--green); margin-left: 8px; text-decoration: underline; }
+.update-banner:focus { outline: none; border-color: var(--focus); box-shadow: 0 0 28px var(--focus-glow); }
+
 .hidden { display: none !important; }
diff --git a/sw.js b/sw.js
new file mode 100644
index 0000000..4b1a4c0
--- /dev/null
+++ b/sw.js
@@ -0,0 +1,55 @@
+var CACHE_NAME = 'stepview-v11';
+var ASSETS = [
+  './',
+  'index.html',
+  'app.js?v=11',
+  'styles.css?v=11',
+  'favicon.svg',
+  'manifest.json'
+];
+
+self.addEventListener('install', function (event) {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then(function (cache) {
+      return cache.addAll(ASSETS);
+    })
+  );
+});
+
+self.addEventListener('activate', function (event) {
+  event.waitUntil(
+    caches.keys().then(function (keys) {
+      return Promise.all(
+        keys.map(function (key) {
+          if (key !== CACHE_NAME) {
+            return caches.delete(key);
+          }
+        })
+      );
+    })
+  );
+});
+
+self.addEventListener('fetch', function (event) {
+  event.respondWith(
+    caches.match(event.request).then(function (response) {
+      if (response) return response;
+      return fetch(event.request).then(function (networkResponse) {
+        if (!networkResponse || networkResponse.status !== 200 || networkResponse.type !== 'basic') {
+          return networkResponse;
+        }
+        var responseToCache = networkResponse.clone();
+        caches.open(CACHE_NAME).then(function (cache) {
+          cache.put(event.request, responseToCache);
+        });
+        return networkResponse;
+      });
+    })
+  );
+});
+
+self.addEventListener('message', function (event) {
+  if (event.data === 'skipWaiting') {
+    self.skipWaiting();
+  }
+});