diff --git a/web/favicon.svg b/web/favicon.svg
new file mode 100644
index 0000000..36ce0a0
--- /dev/null
+++ b/web/favicon.svg
@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 48 48" fill="none"
+     stroke="#3d8bfd" stroke-width="3" stroke-linecap="round" stroke-linejoin="round">
+  <rect x="7" y="16" width="34" height="24" rx="4.5"/>
+  <path d="M8 18.5 24 31 40 18.5"/>
+  <path d="M17 16a7 6.5 0 0 1 14 0"/>
+</svg>
diff --git a/web/index.html b/web/index.html
index 3f801f7..b3823b0 100644
--- a/web/index.html
+++ b/web/index.html
@@ -3,6 +3,7 @@
 <title>schattenpost</title>
 <link rel="manifest" href="manifest.webmanifest">
 <meta name="theme-color" content="#0e1116">
+<link rel="icon" type="image/svg+xml" href="favicon.svg">
 <link rel="apple-touch-icon" href="icon-192.png">
 <style>
   :root {
@@ -19,6 +20,8 @@
     max-width: 640px; margin: 0 auto;
   }
   header { padding: 24px 0 8px; }
+  .brand { display: flex; align-items: center; gap: 12px; }
+  .brand svg { width: 34px; height: 34px; color: var(--accent); flex: 0 0 auto; }
   h1 { font-size: 22px; margin: 0; letter-spacing: .3px; }
   h1 span { color: var(--accent); }
   .sub { color: var(--muted); font-size: 13px; margin-top: 4px; }
@@ -68,7 +71,15 @@
 </style>
 
 <header>
-  <h1>schatten<span>post</span></h1>
+  <div class="brand">
+    <svg viewBox="0 0 48 48" fill="none" stroke="currentColor" stroke-width="2.4"
+         stroke-linecap="round" stroke-linejoin="round" role="img" aria-label="schattenpost Logo">
+      <rect x="7" y="16" width="34" height="24" rx="4.5"/>
+      <path d="M8 18.5 24 31 40 18.5"/>
+      <path d="M17 16a7 6.5 0 0 1 14 0"/>
+    </svg>
+    <h1>schatten<span>post</span></h1>
+  </div>
   <div class="sub">One-Time-Pad + Steganografie. Alles läuft in deinem Browser — nichts wird gesendet.</div>
 </header>
 
diff --git a/web/sw.js b/web/sw.js
index ab03ff1..b805c0d 100644
--- a/web/sw.js
+++ b/web/sw.js
@@ -1,11 +1,12 @@
 /* schattenpost Service Worker — reines Offline-Caching der App-Shell.
    Sendet NICHTS an einen Server. Cache-first, kein Netzwerk-Fallback nötig,
    sobald die Shell einmal geladen ist. */
-const CACHE = 'schattenpost-v3';
+const CACHE = 'schattenpost-v4';
 const SHELL = [
   './',
   './index.html',
   './manifest.webmanifest',
+  './favicon.svg',
   './icon-192.png',
   './icon-512.png',
 ];