diff --git a/customize.dist/messages.js b/customize.dist/messages.js
index 06268dfd3..fd8a5f879 100755
--- a/customize.dist/messages.js
+++ b/customize.dist/messages.js
@@ -29,19 +29,42 @@ var map = {
     'sv': 'Svenska',
     //'te': 'తెలుగు',
     'uk': 'Українська',
-    'zh': '中文(簡體)',
+    'zh': '中文(簡體)', // simplified
+    'zh_Hant': '中文(正體)', // traditional
 };
 
 var Messages = {};
 var LS_LANG = "CRYPTPAD_LANG";
 var getStoredLanguage = function () { return localStorage && localStorage.getItem(LS_LANG); };
 var getBrowserLanguage = function () { return navigator.language || navigator.userLanguage || ''; };
+// Normalize browser/localStorage language labels to CryptPad internal keys.
+// We keep this centralized to avoid scattered `if (l === 'zh') ...` logic.
+var langAliases = {
+    'zh-cn': 'zh',
+    'zh-sg': 'zh',
+    'zh-hans': 'zh',
+
+    'zh-tw': 'zh_Hant',
+    'zh-hk': 'zh_Hant',
+    'zh-mo': 'zh_Hant',
+    'zh-hant': 'zh_Hant',
+};
+var normalizeLanguage = function (l) {
+    if (!l) { return l; }
+    // If it already matches a supported internal key, return as-is.
+    if (map[l]) { return l; }
+    var lLower = String(l).toLowerCase().replace('_', '-');
+    return langAliases[lLower] || l;
+};
 var getLanguage = Messages._getLanguage = function () {
     if (window.cryptpadLanguage) { return window.cryptpadLanguage; }
+
     var l = getBrowserLanguage();
     try {
         l = getStoredLanguage() || getBrowserLanguage();
     } catch (e) { console.log(e); }
+    l = normalizeLanguage(l);
+
     return map[l] ? l :
             (map[l.split('-')[0]] ? l.split('-')[0] :
                 (map[l.split('_')[0]] ? l.split('_')[0] : 'en'));
diff --git a/customize.dist/translations/messages.zh_Hant.js b/customize.dist/translations/messages.zh_Hant.js
new file mode 100644
index 000000000..9b67eba9d
--- /dev/null
+++ b/customize.dist/translations/messages.zh_Hant.js
@@ -0,0 +1,17 @@
+// SPDX-FileCopyrightText: 2026 XWiki CryptPad Team <contact@cryptpad.org> and contributors
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+/*
+ * You can override the translation text using this file.
+ * The recommended method is to make a copy of this file (/customize.dist/translations/messages.{LANG}.js)
+   in a 'customize' directory (/customize/translations/messages.{LANG}.js).
+ * If you want to check all the existing translation keys, you can open the internal language file
+   but you should not change it directly (/common/translations/messages.{LANG}.js)
+*/
+define(['/common/translations/messages.zh_Hant.js'], function (Messages) {
+    // Replace the existing keys in your copied file here:
+    // Messages.button_newpad = "New Rich Text Document";
+
+    return Messages;
+});
diff --git a/www/common/translations/messages.zh_Hant.json.license b/www/common/translations/messages.zh_Hant.json.license
new file mode 100644
index 000000000..c487726db
--- /dev/null
+++ b/www/common/translations/messages.zh_Hant.json.license
@@ -0,0 +1,3 @@
+SPDX-FileCopyrightText: 2026 XWiki CryptPad Team <contact@cryptpad.org> and contributors
+
+SPDX-License-Identifier: AGPL-3.0-or-later