diff --git a/config/prod/domaindata.php b/config/prod/domaindata.php
index 9a70f61..5336c70 100644
--- a/config/prod/domaindata.php
+++ b/config/prod/domaindata.php
@@ -1,10 +1,20 @@
 <?php
 declare(strict_types=1);
 
-// Example: a single "brand" domain name.
-// In real deployments you might derive this from ENV or hostnames.
+// Domain steering by TLD (.de/.at/.ch/.info)
+$host = $_SERVER['HTTP_HOST'] ?? '';
+$allowedTlds = ['de','at','ch','info'];
+$tld = 'info';
+if (preg_match('/\\.(de|at|ch|info)$/i', $host, $m)) {
+    $tld = strtolower($m[1]);
+}
+if (!in_array($tld, $allowedTlds, true)) {
+    $tld = 'info';
+}
+$baseDomain = 'papa-kind-treff.' . $tld;
+
 if (!defined('APP_DOMAIN_NAME')) {
-    define('APP_DOMAIN_NAME', 'papa-kind-treff.info');
+    define('APP_DOMAIN_NAME', $baseDomain);
 }
 
 if (!defined('APP_PREFIX')) {
diff --git a/config/staging/domaindata.php b/config/staging/domaindata.php
index 09426f6..148478d 100644
--- a/config/staging/domaindata.php
+++ b/config/staging/domaindata.php
@@ -1,10 +1,21 @@
 <?php
 declare(strict_types=1);
 
-// Example: a single "brand" domain name.
-// In real deployments you might derive this from ENV or hostnames.
+// Domain steering by TLD (.de/.at/.ch/.info)
+$host = $_SERVER['HTTP_HOST'] ?? '';
+$allowedTlds = ['de','at','ch','info'];
+$tld = 'info';
+if (preg_match('/\\.(de|at|ch|info)$/i', $host, $m)) {
+    $tld = strtolower($m[1]);
+}
+if (!in_array($tld, $allowedTlds, true)) {
+    $tld = 'info';
+}
+$baseDomain = 'papa-kind-treff.' . $tld;
+$fullDomain = 'staging.' . $baseDomain;
+
 if (!defined('APP_DOMAIN_NAME')) {
-    define('APP_DOMAIN_NAME', 'staging.papa-kind-treff.info');
+    define('APP_DOMAIN_NAME', $fullDomain);
 }
 
 if (!defined('APP_PREFIX')) {
diff --git a/partials/structure/layout_start.php b/partials/structure/layout_start.php
index 86e6274..439f8f3 100644
--- a/partials/structure/layout_start.php
+++ b/partials/structure/layout_start.php
@@ -34,6 +34,18 @@ if ($debugEnabled) {
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title><?= htmlspecialchars(t('common.title'), ENT_QUOTES) ?></title>
   <meta name="description" content="Papa-Kind-Treff: Väter vernetzen sich für Treffen mit und ohne Kinder, Events in der Nähe entdecken und sicher Kontakte knüpfen.">
+  <?php
+    $canonicalHost = APP_DOMAIN_NAME ?? ($_SERVER['HTTP_HOST'] ?? 'papa-kind-treff.info');
+    $scheme = (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off') ? 'https' : 'https';
+    $canonical = $scheme . '://' . $canonicalHost . ($_SERVER['REQUEST_URI'] ?? '/');
+    $tlds = ['de' => 'papa-kind-treff.de', 'at' => 'papa-kind-treff.at', 'ch' => 'papa-kind-treff.ch', 'info' => 'papa-kind-treff.info'];
+  ?>
+  <link rel="canonical" href="<?= htmlspecialchars($canonical, ENT_QUOTES) ?>">
+  <link rel="alternate" hreflang="de-DE" href="https://<?= $tlds['de'] ?>/">
+  <link rel="alternate" hreflang="de-CH" href="https://<?= $tlds['ch'] ?>/">
+  <link rel="alternate" hreflang="de-AT" href="https://<?= $tlds['at'] ?>/">
+  <link rel="alternate" hreflang="de" href="https://<?= $tlds['info'] ?>/">
+  <link rel="alternate" hreflang="en" href="https://<?= $tlds['info'] ?>/">
   <?php asset_styles(); ?>
   <?php asset_scripts('header'); ?>
 </head>