diff --git a/Doku/architecture.md b/Doku/architecture.md
index 6add09a..76dc387 100644
--- a/Doku/architecture.md
+++ b/Doku/architecture.md
@@ -96,3 +96,23 @@ Stage 3  alpine:3.21      nur Binary, ca-certificates, tzdata
 Die angezeigte Version (Kopf der App) setzt der Build-Parameter `APP_VERSION`: Die CI übergibt bei Git-Tags den Tag-Namen (`v0.2`), sonst zeigt die App die Version aus `frontend/package.json` mit `-dev` (`v0.2-dev`). Umgesetzt in `frontend/vite.config.ts` und `frontend/src/version.ts`.
 
 Die Tests laufen beim Image-Build (Frontend: `npm run test:run`, Backend: `go test -v ./...`); ein Fehler bricht den Build ab. Frontend-Tests liegen unter `frontend/src/**/__tests__/` (Vitest + jsdom + Testing Library, Setup in `frontend/src/test/setup.ts`).
+
+## App-Icons, PWA & Social-Preview (Open Graph)
+
+MindSift verwendet plattformübergreifend ein einheitliches App-Icon-Design, das exakt dem Icon im Kopfbereich der mobilen App entspricht:
+- **Design & Geometrie:** Sanft abgerundetes Quadrat (`rx=108` auf 512x512 Canvas bzw. `rounded-xl`), Primärblau (`--accent-primary: #2563eb`) als Hintergrund und zentriertes Lucide Brain Icon in reinem Weiß (`--text-on-accent: #ffffff`).
+
+### Asset-Matrix (`frontend/public/`)
+
+| Datei | Zweck & Zielplattform | Besonderheit |
+|---|---|---|
+| `icon.svg` | Modernes Standard-Icon & SVG-Favicon | Vektor-Original mit abgerundeten Ecken |
+| `icon-192x192.png`, `icon-512x512.png` | PWA-Installation (`purpose: "any"`), Desktop Linux/Windows | Erforderlich für Chromium unter Linux (erzeugt sonst kein `.desktop`-Icon) |
+| `icon-maskable-192x192.png`, `icon-maskable-512x512.png`, `icon-maskable.svg` | Android Adaptive Icons (`purpose: "maskable"`) | Full-Bleed Hintergrund (`#2563eb`) ohne transparente Ecken, Brain im 80%-Sicherheitsbereich |
+| `apple-touch-icon.png` (180x180) | iOS Safari („Zum Home-Bildschirm“) | Opaker Hintergrund verhindert schwarze Ränder beim automatischen Apple-Squircle-Maskieren |
+| `favicon.ico`, `favicon-32x32.png`, `favicon-16x16.png` | Browser-Tabs, Lesezeichen, Chronik | Multi-Resolution-ICO (16/32/48) für alle Desktop-Browser |
+| `og-image.png` (1200x630), `og-image-square.png` (512x512) | Link-Vorschau in WhatsApp, Discord, Telegram, X/Twitter | Dunkler `#0b0f19`-Hintergrund mit Icon & Claim; Datei-Größe < 120 KB (WhatsApp-Limit < 300 KB) |
+
+### Dynamische OpenGraph-URL-Injektion
+
+Messenger-Crawler (insbesondere WhatsApp) werten relative Bild-URLs in `og:image` oft nicht korrekt aus. Der Go-SPA-Handler in [`internal/api/server.go`](../internal/api/server.go) ersetzt beim Ausliefern von `index.html` automatisch relative Pfade (`/og-image.png`, `og:url`) durch die absolute Server-Origin (`scheme://host`), ermittelt über `X-Forwarded-Proto` und `X-Forwarded-Host` bzw. `req.Host`.
diff --git a/Doku/theming.md b/Doku/theming.md
index bcf387e..6a1d755 100644
--- a/Doku/theming.md
+++ b/Doku/theming.md
@@ -97,6 +97,9 @@ In [`frontend/src/index.css`](../frontend/src/index.css) und `tailwind.config.js
 - `.checkbox-square`: Kontrollkästchen mit `--radius-checkbox`.
 - `.capture-pill`: Spezial-Pille für die Desktop-Schnelleingabeleiste mit `--radius-pill`.
 
+### 🏷️ App-Icon & Branding
+Das standardmäßige Marken-Icon von MindSift (`frontend/public/icon.svg`, PWA-Icons und Social-Preview-Bilder) folgt der primären Akzentfarbe `--accent: #2563eb` und `--text-on-accent: #ffffff` mit den typischen leichten Eckenrundungen (`rounded-xl` bzw. `rx=108`). Details zur Asset-Matrix und den Icon-Formaten siehe [architecture.md](architecture.md#app-icons-pwa--social-preview-open-graph).
+
 ---
 
 ## 🛠️ 5. Ein eigenes Theme erstellen
diff --git a/frontend/index.html b/frontend/index.html
index d0175fd..97f14bb 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -9,9 +9,35 @@
     <meta name="apple-mobile-web-app-title" content="MindSift" />
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
     <meta name="description" content="MindSift — Der Kopf frei in drei Sekunden. Instant Capture, Tinder-Style Triage, Workspace & Echtzeit-Listen." />
-    <link rel="manifest" href="/manifest.json" />
+    
+    <!-- Favicon & Touch Icons -->
     <link rel="icon" type="image/svg+xml" href="/icon.svg" />
-    <link rel="apple-touch-icon" href="/icon.svg" />
+    <link rel="icon" type="image/png" sizes="32x32" href="/favicon-32x32.png" />
+    <link rel="icon" type="image/png" sizes="16x16" href="/favicon-16x16.png" />
+    <link rel="shortcut icon" href="/favicon.ico" />
+    <link rel="apple-touch-icon" sizes="180x180" href="/apple-touch-icon.png" />
+
+    <!-- Open Graph / WhatsApp / Discord / Facebook -->
+    <meta property="og:type" content="website" />
+    <meta property="og:site_name" content="MindSift" />
+    <meta property="og:url" content="/" />
+    <meta property="og:title" content="MindSift — Der Kopf frei in drei Sekunden" />
+    <meta property="og:description" content="Instant Brain-Dump, Tinder-Style Triage, Workspace & Echtzeit-Listen." />
+    <meta property="og:image" content="/og-image.png" />
+    <meta property="og:image:secure_url" content="/og-image.png" />
+    <meta property="og:image:type" content="image/png" />
+    <meta property="og:image:width" content="1200" />
+    <meta property="og:image:height" content="630" />
+    <meta property="og:image:alt" content="MindSift App Logo & Vorschau" />
+
+    <!-- Twitter / X -->
+    <meta name="twitter:card" content="summary_large_image" />
+    <meta name="twitter:title" content="MindSift — Der Kopf frei in drei Sekunden" />
+    <meta name="twitter:description" content="Instant Brain-Dump, Tinder-Style Triage, Workspace & Echtzeit-Listen." />
+    <meta name="twitter:image" content="/og-image.png" />
+    <meta name="twitter:image:alt" content="MindSift App Logo & Vorschau" />
+
+    <link rel="manifest" href="/manifest.json" />
     <title>MindSift</title>
     <script>
       window.__deferredPwaPrompt = null;
diff --git a/frontend/public/apple-touch-icon.png b/frontend/public/apple-touch-icon.png
new file mode 100644
index 0000000..22f052b
Binary files /dev/null and b/frontend/public/apple-touch-icon.png differ
diff --git a/frontend/public/favicon-16x16.png b/frontend/public/favicon-16x16.png
new file mode 100644
index 0000000..10ea9d5
Binary files /dev/null and b/frontend/public/favicon-16x16.png differ
diff --git a/frontend/public/favicon-32x32.png b/frontend/public/favicon-32x32.png
new file mode 100644
index 0000000..9e14833
Binary files /dev/null and b/frontend/public/favicon-32x32.png differ
diff --git a/frontend/public/favicon.ico b/frontend/public/favicon.ico
new file mode 100644
index 0000000..d7b4be0
Binary files /dev/null and b/frontend/public/favicon.ico differ
diff --git a/frontend/public/icon-192x192.png b/frontend/public/icon-192x192.png
new file mode 100644
index 0000000..2f8fc39
Binary files /dev/null and b/frontend/public/icon-192x192.png differ
diff --git a/frontend/public/icon-512x512.png b/frontend/public/icon-512x512.png
new file mode 100644
index 0000000..b4acfd0
Binary files /dev/null and b/frontend/public/icon-512x512.png differ
diff --git a/frontend/public/icon-maskable-192x192.png b/frontend/public/icon-maskable-192x192.png
new file mode 100644
index 0000000..800f406
Binary files /dev/null and b/frontend/public/icon-maskable-192x192.png differ
diff --git a/frontend/public/icon-maskable-512x512.png b/frontend/public/icon-maskable-512x512.png
new file mode 100644
index 0000000..e685706
Binary files /dev/null and b/frontend/public/icon-maskable-512x512.png differ
diff --git a/frontend/public/icon-maskable.svg b/frontend/public/icon-maskable.svg
new file mode 100644
index 0000000..cd09a7a
--- /dev/null
+++ b/frontend/public/icon-maskable.svg
@@ -0,0 +1,14 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="512" height="512">
+  <rect width="512" height="512" fill="#2563eb"/>
+  <g transform="translate(256, 256) scale(11) translate(-12, -12)" fill="none" stroke="#ffffff" stroke-width="2.1" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M12 5a3 3 0 1 0-5.997.125 4 4 0 0 0-2.526 5.77 4 4 0 0 0 .556 6.588A4 4 0 1 0 12 18Z"/>
+    <path d="M12 5a3 3 0 1 1 5.997.125 4 4 0 0 1 2.526 5.77 4 4 0 0 1-.556 6.588A4 4 0 1 1 12 18Z"/>
+    <path d="M15 13a4.5 4.5 0 0 1-3-4 4.5 4.5 0 0 1-3 4"/>
+    <path d="M17.599 6.5a3 3 0 0 0 .399-1.375"/>
+    <path d="M6.003 5.125A3 3 0 0 0 6.401 6.5"/>
+    <path d="M3.477 10.896a4 4 0 0 1 .585-.396"/>
+    <path d="M19.938 10.5a4 4 0 0 1 .585.396"/>
+    <path d="M6 18a4 4 0 0 1-1.967-.516"/>
+    <path d="M19.967 17.484A4 4 0 0 1 18 18"/>
+  </g>
+</svg>
\ No newline at end of file
diff --git a/frontend/public/icon.svg b/frontend/public/icon.svg
index 57e8419..75e2a63 100644
--- a/frontend/public/icon.svg
+++ b/frontend/public/icon.svg
@@ -1,6 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" width="512" height="512">
-  <rect width="512" height="512" rx="128" fill="#8ab4f8"/>
-  <g transform="translate(80, 80) scale(14.666)" fill="none" stroke="#0b0f19" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+  <rect width="512" height="512" rx="108" fill="#2563eb"/>
+  <g transform="translate(256, 256) scale(12.5) translate(-12, -12)" fill="none" stroke="#ffffff" stroke-width="2.1" stroke-linecap="round" stroke-linejoin="round">
     <path d="M12 5a3 3 0 1 0-5.997.125 4 4 0 0 0-2.526 5.77 4 4 0 0 0 .556 6.588A4 4 0 1 0 12 18Z"/>
     <path d="M12 5a3 3 0 1 1 5.997.125 4 4 0 0 1 2.526 5.77 4 4 0 0 1-.556 6.588A4 4 0 1 1 12 18Z"/>
     <path d="M15 13a4.5 4.5 0 0 1-3-4 4.5 4.5 0 0 1-3 4"/>
@@ -11,4 +11,4 @@
     <path d="M6 18a4 4 0 0 1-1.967-.516"/>
     <path d="M19.967 17.484A4 4 0 0 1 18 18"/>
   </g>
-</svg>
+</svg>
\ No newline at end of file
diff --git a/frontend/public/manifest.json b/frontend/public/manifest.json
index 6c1cbb7..4684fc7 100644
--- a/frontend/public/manifest.json
+++ b/frontend/public/manifest.json
@@ -17,8 +17,32 @@
       "purpose": "any"
     },
     {
-      "src": "/icon.svg",
-      "sizes": "192x192 512x512",
+      "src": "/icon-192x192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icon-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/icon-maskable-192x192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "/icon-maskable-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    },
+    {
+      "src": "/icon-maskable.svg",
+      "sizes": "any",
       "type": "image/svg+xml",
       "purpose": "maskable"
     }
diff --git a/frontend/public/og-image-square.png b/frontend/public/og-image-square.png
new file mode 100644
index 0000000..bfdbdda
Binary files /dev/null and b/frontend/public/og-image-square.png differ
diff --git a/frontend/public/og-image.png b/frontend/public/og-image.png
new file mode 100644
index 0000000..0666754
Binary files /dev/null and b/frontend/public/og-image.png differ
diff --git a/internal/api/server.go b/internal/api/server.go
index 697c544..1545f67 100644
--- a/internal/api/server.go
+++ b/internal/api/server.go
@@ -254,6 +254,29 @@ func (s *Server) Router() http.Handler {
 				w.Header().Set("Pragma", "no-cache")
 				w.Header().Set("Expires", "0")
 			}
+			if path == "index.html" {
+				if data, err := fs.ReadFile(s.staticFS, "index.html"); err == nil {
+					scheme := "http"
+					if req.TLS != nil || req.Header.Get("X-Forwarded-Proto") == "https" {
+						scheme = "https"
+					}
+					host := req.Header.Get("X-Forwarded-Host")
+					if host == "" {
+						host = req.Host
+					}
+					if host != "" {
+						origin := scheme + "://" + host
+						htmlStr := string(data)
+						htmlStr = strings.ReplaceAll(htmlStr, `content="/og-image.png"`, `content="`+origin+`/og-image.png"`)
+						htmlStr = strings.ReplaceAll(htmlStr, `property="og:url" content="/"`, `property="og:url" content="`+origin+`/"`)
+						data = []byte(htmlStr)
+					}
+					w.Header().Set("Content-Type", "text/html; charset=utf-8")
+					w.WriteHeader(http.StatusOK)
+					_, _ = w.Write(data)
+					return
+				}
+			}
 			fileServer.ServeHTTP(w, req)
 		})
 	}