diff --git a/extension/_locales/de/messages.json b/extension/_locales/de/messages.json
index 8b84354..f7bf757 100644
--- a/extension/_locales/de/messages.json
+++ b/extension/_locales/de/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Synchronisiere die Videowiedergabe auf YouTube, Netflix, Emby, Jellyfin und jeder HTML5-Seite in Echtzeit mit Freunden."
+    "message": "Erstelle private Watch Partys und synchronisiere Videos mit Freunden auf YouTube, Netflix, Jellyfin, Emby und fast jeder Website."
   }
 }
diff --git a/extension/_locales/en/messages.json b/extension/_locales/en/messages.json
index 3132906..8be2507 100644
--- a/extension/_locales/en/messages.json
+++ b/extension/_locales/en/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Synchronize video playback on YouTube, Netflix, Emby, Jellyfin, and any HTML5 site in real-time with friends."
+    "message": "Create private watch parties and sync videos with friends on YouTube, Netflix, Jellyfin, Emby, and almost any HTML5 website."
   }
 }
diff --git a/extension/_locales/es/messages.json b/extension/_locales/es/messages.json
index d716d3e..9125cab 100644
--- a/extension/_locales/es/messages.json
+++ b/extension/_locales/es/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Mira videos junto a tus amigos en perfecta sincronización. Compatible con Netflix, YouTube, Twitch, Prime Video, Disney+ y cualquier reproductor HTML5."
+    "message": "Crea fiestas privadas y sincroniza vídeos con amigos en YouTube, Netflix, Jellyfin, Emby y casi cualquier sitio HTML5."
   }
 }
diff --git a/extension/_locales/fr/messages.json b/extension/_locales/fr/messages.json
index 37cbe71..ce17b61 100644
--- a/extension/_locales/fr/messages.json
+++ b/extension/_locales/fr/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Synchronisez la lecture vidéo sur YouTube, Netflix, Emby, Jellyfin et tout site HTML5 en temps réel avec vos amis."
+    "message": "Créez des watch parties privées et regardez en synchro entre amis sur YouTube, Netflix, Jellyfin, Emby et presque tout site HTML5."
   }
 }
diff --git a/extension/_locales/it/messages.json b/extension/_locales/it/messages.json
index 118ff90..4f6aa8a 100644
--- a/extension/_locales/it/messages.json
+++ b/extension/_locales/it/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Sincronizza la riproduzione video su YouTube, Netflix, Emby, Jellyfin e qualsiasi sito HTML5 in tempo reale con gli amici."
+    "message": "Crea watch party private e sincronizza i video con gli amici su YouTube, Netflix, Jellyfin, Emby e quasi ogni sito HTML5."
   }
 }
diff --git a/extension/_locales/ja/messages.json b/extension/_locales/ja/messages.json
index 5833c2f..dc17ce0 100644
--- a/extension/_locales/ja/messages.json
+++ b/extension/_locales/ja/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "YouTube、Netflix、Emby、Jellyfin、その他HTML5サイトでの動画再生を友達とリアルタイムで同期します。"
+    "message": "プライベートなウォッチパーティーを作成し、YouTube、Netflix、Jellyfin、EmbyやほぼすべてのHTML5サイトで友達と動画を同期再生できます。"
   }
 }
diff --git a/extension/_locales/ko/messages.json b/extension/_locales/ko/messages.json
index 12f71e4..8ad21bb 100644
--- a/extension/_locales/ko/messages.json
+++ b/extension/_locales/ko/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "YouTube, Netflix, Emby, Jellyfin 및 모든 HTML5 사이트에서 친구들과 실시간으로 비디오 재생을 동기화하세요."
+    "message": "비공개 Watch Party를 만들고 YouTube, Netflix, Jellyfin, Emby 및 거의 모든 HTML5 사이트에서 친구들과 영상을 동기화하세요."
   }
 }
diff --git a/extension/_locales/nl/messages.json b/extension/_locales/nl/messages.json
index ab97481..feb4563 100644
--- a/extension/_locales/nl/messages.json
+++ b/extension/_locales/nl/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Synchroniseer video-afspelen op YouTube, Netflix, Emby, Jellyfin en elke HTML5-site in realtime met vrienden."
+    "message": "Maak privéwatchparty's en kijk synchroon met vrienden op YouTube, Netflix, Jellyfin, Emby en vrijwel elke HTML5-website."
   }
 }
diff --git a/extension/_locales/pl/messages.json b/extension/_locales/pl/messages.json
index e13b068..8f50d12 100644
--- a/extension/_locales/pl/messages.json
+++ b/extension/_locales/pl/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Synchronizuj odtwarzanie wideo na YouTube, Netflix, Emby, Jellyfin i dowolnej stronie HTML5 w czasie rzeczywistym ze znajomymi."
+    "message": "Twórz prywatne wspólne seanse i synchronizuj filmy ze znajomymi na YouTube, Netflix, Jellyfin, Emby i niemal każdej stronie HTML5."
   }
 }
diff --git a/extension/_locales/pt_BR/messages.json b/extension/_locales/pt_BR/messages.json
index 7c3103e..5c2cbee 100644
--- a/extension/_locales/pt_BR/messages.json
+++ b/extension/_locales/pt_BR/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Assista a vídeos junto com seus amigos em sincronia perfeita. Compatível com Netflix, YouTube, Twitch, Prime Video, Disney+ e qualquer player HTML5."
+    "message": "Crie watch parties privadas e sincronize vídeos com amigos no YouTube, Netflix, Jellyfin, Emby e em quase qualquer site HTML5."
   }
 }
diff --git a/extension/_locales/pt_PT/messages.json b/extension/_locales/pt_PT/messages.json
index 506b8a3..d4285a4 100644
--- a/extension/_locales/pt_PT/messages.json
+++ b/extension/_locales/pt_PT/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Veja vídeos em conjunto com os seus amigos em sincronia perfeita. Compatível com Netflix, YouTube, Twitch, Prime Video, Disney+ e qualquer leitor HTML5."
+    "message": "Crie sessões privadas e veja vídeos sincronizados com amigos no YouTube, Netflix, Jellyfin, Emby e em quase qualquer site HTML5."
   }
 }
diff --git a/extension/_locales/ru/messages.json b/extension/_locales/ru/messages.json
index ff73697..5360023 100644
--- a/extension/_locales/ru/messages.json
+++ b/extension/_locales/ru/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Синхронизируйте воспроизведение видео на YouTube, Netflix, Emby, Jellyfin и любых HTML5-сайтах в реальном времени с друзьями."
+    "message": "Создавайте закрытые Watch Party и смотрите синхронно с друзьями на YouTube, Netflix, Jellyfin, Emby и почти любом сайте HTML5."
   }
 }
diff --git a/extension/_locales/tr/messages.json b/extension/_locales/tr/messages.json
index 7641824..236642c 100644
--- a/extension/_locales/tr/messages.json
+++ b/extension/_locales/tr/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "YouTube, Netflix, Emby, Jellyfin ve herhangi bir HTML5 sitesinde video oynatmayı arkadaşlarınızla gerçek zamanlı olarak senkronize edin."
+    "message": "Özel izleme partileri kurun; YouTube, Netflix, Jellyfin, Emby ve çoğu HTML5 sitesinde arkadaşlarınızla senkron izleyin."
   }
 }
diff --git a/extension/_locales/uk/messages.json b/extension/_locales/uk/messages.json
index 4e1fea2..8aee6c0 100644
--- a/extension/_locales/uk/messages.json
+++ b/extension/_locales/uk/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "Синхронізуйте відтворення відео на YouTube, Netflix, Emby, Jellyfin і будь-якому сайті HTML5 у режимі реального часу з друзями."
+    "message": "Створюйте закриті Watch Party й дивіться синхронно з друзями на YouTube, Netflix, Jellyfin, Emby та майже будь-якому сайті HTML5."
   }
 }
diff --git a/extension/_locales/zh_CN/messages.json b/extension/_locales/zh_CN/messages.json
index 8b40486..6717048 100644
--- a/extension/_locales/zh_CN/messages.json
+++ b/extension/_locales/zh_CN/messages.json
@@ -1,8 +1,8 @@
 {
   "appName": {
-    "message": "KoalaSync"
+    "message": "Watch Party - KoalaSync"
   },
   "appDesc": {
-    "message": "与朋友实时同步YouTube、Netflix、Emby、Jellyfin和任何HTML5网站上的视频播放。"
+    "message": "创建私人观影派对，与好友在 YouTube、Netflix、Jellyfin、Emby 及几乎任何 HTML5 视频网站同步观看。"
   }
 }
diff --git a/extension/manifest.base.json b/extension/manifest.base.json
index aa61218..3948b08 100644
--- a/extension/manifest.base.json
+++ b/extension/manifest.base.json
@@ -1,9 +1,10 @@
 {
   "manifest_version": 3,
   "default_locale": "en",
-  "name": "KoalaSync",
+  "name": "__MSG_appName__",
+  "short_name": "KoalaSync",
   "version": "2.6.3",
-  "description": "Synchronize video playback on YouTube, Netflix, Emby, Jellyfin, and any HTML5 site in real-time with friends.",
+  "description": "__MSG_appDesc__",
   "permissions": [
     "storage",
     "tabs",
diff --git a/scripts/build-extension.cjs b/scripts/build-extension.cjs
index b5d9ac6..2fa56ae 100644
--- a/scripts/build-extension.cjs
+++ b/scripts/build-extension.cjs
@@ -6,6 +6,59 @@ const rootDir = path.join(__dirname, '..');
 const extDir = path.join(rootDir, 'extension');
 const distDir = path.join(rootDir, 'dist');
 const baseManifestPath = path.join(extDir, 'manifest.base.json');
+const localesDir = path.join(extDir, '_locales');
+const requiredAppName = 'Watch Party - KoalaSync';
+const maxAppNameLength = 75;
+const maxAppDescLength = 132;
+
+function countUnicodeCharacters(value) {
+  return Array.from(value).length;
+}
+
+function validateExtensionMetadata() {
+  const localeDirectories = fs.readdirSync(localesDir, { withFileTypes: true })
+    .filter((entry) => entry.isDirectory())
+    .map((entry) => entry.name)
+    .sort();
+
+  for (const locale of localeDirectories) {
+    const messagesPath = path.join(localesDir, locale, 'messages.json');
+    let messages;
+
+    try {
+      messages = JSON.parse(fs.readFileSync(messagesPath, 'utf8'));
+    } catch (error) {
+      throw new Error(`CRITICAL: Invalid locale JSON at _locales/${locale}/messages.json: ${error.message}`);
+    }
+
+    if (!messages || typeof messages !== 'object' || Array.isArray(messages)) {
+      throw new Error(`CRITICAL: _locales/${locale}/messages.json must contain a JSON object`);
+    }
+
+    for (const key of ['appName', 'appDesc']) {
+      if (!messages[key] || typeof messages[key].message !== 'string' || messages[key].message.trim().length === 0) {
+        throw new Error(`CRITICAL: _locales/${locale}/messages.json is missing a valid ${key}.message`);
+      }
+    }
+
+    const appNameLength = countUnicodeCharacters(messages.appName.message);
+    const appDescLength = countUnicodeCharacters(messages.appDesc.message);
+
+    if (appNameLength > maxAppNameLength) {
+      throw new Error(`CRITICAL: _locales/${locale}/messages.json appName.message is ${appNameLength} characters; maximum is ${maxAppNameLength}`);
+    }
+    if (messages.appName.message !== requiredAppName) {
+      throw new Error(`CRITICAL: _locales/${locale}/messages.json appName.message must exactly equal "${requiredAppName}"`);
+    }
+    if (appDescLength > maxAppDescLength) {
+      throw new Error(`CRITICAL: _locales/${locale}/messages.json appDesc.message is ${appDescLength} characters; maximum is ${maxAppDescLength}`);
+    }
+  }
+
+  console.log(`✓ Validated localized extension metadata for ${localeDirectories.length} locales`);
+}
+
+validateExtensionMetadata();
 
 // Ensure dist directory exists
 if (fs.existsSync(distDir)) {