diff --git a/index.html b/index.html
index d969e13..ef4afbd 100755
--- a/index.html
+++ b/index.html
@@ -889,6 +889,20 @@
 
         let currentLang = 'vi';
 
+        function getPreferredLanguage() {
+            const supported = Object.keys(translations);
+            const preferences = navigator.languages?.length
+                ? navigator.languages
+                : [navigator.language];
+
+            for (const locale of preferences) {
+                const language = locale.toLowerCase().split(/[-_]/)[0];
+                if (supported.includes(language)) return language;
+            }
+
+            return 'vi';
+        }
+
         function setLanguage(lang) {
             currentLang = lang;
             document.querySelectorAll('[data-i18n]').forEach(el => {
@@ -964,8 +978,8 @@
             document.getElementById('success-modal').classList.add('hidden');
         }
 
-        // Initialize default language
-        setLanguage('vi');
+        // Initialize from browser language preferences
+        setLanguage(getPreferredLanguage());
     </script>
 </body>
 </html>
\ No newline at end of file