diff --git a/public/index.html b/public/index.html
index 3748202..901e3e5 100644
--- a/public/index.html
+++ b/public/index.html
@@ -4,7 +4,52 @@
   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover" />
   <meta name="theme-color" content="#0B0B09" />
-  <title>Cipher — a Radical Party project</title>
+  <title>Cipher — Free End-to-End Encrypted Messenger | Private Chat, Calls &amp; Groups</title>
+  <meta name="description" content="Cipher is a free, private, end-to-end encrypted messenger. Signal-grade encrypted 1:1 and group chats, voice &amp; video calls, and disappearing messages — your keys never leave your device. No phone number required." />
+  <meta name="keywords" content="encrypted messenger, end-to-end encryption, private messaging, secure chat, encrypted calls, disappearing messages, Signal alternative, WhatsApp alternative, E2E encryption, private group chat" />
+  <meta name="author" content="Radical Party" />
+  <meta name="robots" content="index, follow, max-image-preview:large" />
+  <link rel="canonical" href="https://cipher.theradicalparty.com/" />
+
+  <!-- Open Graph / social -->
+  <meta property="og:type" content="website" />
+  <meta property="og:site_name" content="Cipher" />
+  <meta property="og:title" content="Cipher — Free End-to-End Encrypted Messenger" />
+  <meta property="og:description" content="Private, end-to-end encrypted chats, groups, and voice &amp; video calls. Your keys never leave your device. No phone number required." />
+  <meta property="og:url" content="https://cipher.theradicalparty.com/" />
+  <meta property="og:image" content="https://cipher.theradicalparty.com/icons/icon.svg" />
+  <meta name="twitter:card" content="summary_large_image" />
+  <meta name="twitter:title" content="Cipher — Free End-to-End Encrypted Messenger" />
+  <meta name="twitter:description" content="Private, end-to-end encrypted chats, groups, and voice &amp; video calls. Your keys never leave your device." />
+  <meta name="twitter:image" content="https://cipher.theradicalparty.com/icons/icon.svg" />
+
+  <!-- Structured data: helps Google understand this is a messaging web app -->
+  <script type="application/ld+json">
+  {
+    "@context": "https://schema.org",
+    "@type": "WebApplication",
+    "name": "Cipher",
+    "url": "https://cipher.theradicalparty.com/",
+    "applicationCategory": "CommunicationApplication",
+    "operatingSystem": "Web, iOS, Android, Windows, macOS, Linux",
+    "browserRequirements": "Requires JavaScript. Requires a modern browser.",
+    "description": "Cipher is a free, end-to-end encrypted messenger with private 1:1 and group chats, encrypted voice and video calls, and disappearing messages. Private keys are generated on-device and never sent to the server.",
+    "isAccessibleForFree": true,
+    "offers": { "@type": "Offer", "price": "0", "priceCurrency": "USD" },
+    "featureList": [
+      "End-to-end encryption (Signal Protocol)",
+      "Private one-to-one and group chats",
+      "Encrypted voice and video calls",
+      "Disappearing messages",
+      "Read receipts",
+      "Group invite links",
+      "Multi-device with QR linking",
+      "No phone number required"
+    ],
+    "publisher": { "@type": "Organization", "name": "Radical Party" }
+  }
+  </script>
+
   <link rel="manifest" href="/manifest.webmanifest" />
   <link rel="icon" href="/icons/icon.svg" type="image/svg+xml" />
   <link rel="apple-touch-icon" href="/icons/icon.svg" />
@@ -267,7 +312,26 @@
   </style>
 </head>
 <body>
-  <div id="app"></div>
+  <div id="app">
+    <!-- Server-visible content for crawlers / no-JS. The real app hydrates over this. -->
+    <noscript>
+      <h1>Cipher — Free End-to-End Encrypted Messenger</h1>
+      <p>Cipher is a free, private messenger with end-to-end encryption built on the
+      Signal Protocol. Chat one-to-one or in groups, make encrypted voice and video
+      calls, and send disappearing messages. Your private keys are generated on your
+      device and never leave it — the server only ever relays ciphertext.</p>
+      <h2>Features</h2>
+      <ul>
+        <li>End-to-end encrypted 1:1 and group chats</li>
+        <li>Encrypted voice and video calls</li>
+        <li>Disappearing messages and read receipts</li>
+        <li>Shareable group invite links</li>
+        <li>Multi-device sync with QR linking</li>
+        <li>No phone number required</li>
+      </ul>
+      <p>Cipher requires JavaScript. Please enable it to sign in or create an account.</p>
+    </noscript>
+  </div>
   <script type="module" src="/js/app.js"></script>
 </body>
 </html>
diff --git a/public/robots.txt b/public/robots.txt
new file mode 100644
index 0000000..97c2178
--- /dev/null
+++ b/public/robots.txt
@@ -0,0 +1,7 @@
+# Cipher — allow crawling of the public app shell; keep the API out of the index.
+# JS/CSS are intentionally crawlable so Google can render the single-page app.
+User-agent: *
+Allow: /
+Disallow: /api/
+
+Sitemap: https://cipher.theradicalparty.com/sitemap.xml
diff --git a/public/sitemap.xml b/public/sitemap.xml
new file mode 100644
index 0000000..def12e5
--- /dev/null
+++ b/public/sitemap.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+  <url>
+    <loc>https://cipher.theradicalparty.com/</loc>
+    <lastmod>2026-07-22</lastmod>
+    <changefreq>weekly</changefreq>
+    <priority>1.0</priority>
+  </url>
+</urlset>
diff --git a/public/sw.js b/public/sw.js
index e3b7535..4e525e5 100644
--- a/public/sw.js
+++ b/public/sw.js
@@ -1,7 +1,7 @@
 // Service worker: offline app shell + Web Push wake-up.
 // It never touches message plaintext — decryption happens only in the page.
 
-const CACHE = "cipher-v10";
+const CACHE = "cipher-v11";
 const SHELL = [
   "/",
   "/index.html",
