diff --git a/app.php b/app.php
index 71a1800..e193960 100644
--- a/app.php
+++ b/app.php
@@ -1,14 +1,19 @@
 <?php
 
+setlocale(LC_ALL, "");
+
 $f3 = require(__DIR__.'/vendor/fatfree/base.php');
 
+$f3->set('FALLBACK', null);
+$f3->language($f3->get('HEADERS')['Accept-Language']);
+
 session_start();
 
 if(getenv("DEBUG")) {
     $f3->set('DEBUG', getenv("DEBUG"));
 }
 
-$f3->set('LANGUAGES',
+$f3->set('SUPPORTED_LANGUAGES',
     ['fr' => 'Français',
         'en' => 'English',
         'ar' => 'العربية']);
@@ -34,12 +39,11 @@ if($f3->get('DISABLE_ORGANIZATION')) {
 }
 
 if ($f3->get('GET.lang')) {
-    $lang = $f3->get('GET.lang');
-    changeLanguage($lang, $f3);
-} elseif (isset($_SESSION['LANGUAGE'])) {
-    changeLanguage($_SESSION['LANGUAGE'], $f3);
+    selectLanguage($f3->get('GET.lang'), $f3, true);
 } elseif (isset($_COOKIE['LANGUAGE'])) {
-    changeLanguage($_COOKIE['LANGUAGE'], $f3);
+    selectLanguage($_COOKIE['LANGUAGE'], $f3, true);
+} else {
+    selectLanguage($f3->get('LANGUAGE'), $f3);
 }
 
 $domain = basename(glob($f3->get('ROOT')."/locale/application_*.pot")[0], '.pot');
@@ -47,13 +51,6 @@ $domain = basename(glob($f3->get('ROOT')."/locale/application_*.pot")[0], '.pot'
 bindtextdomain($domain, $f3->get('ROOT')."/locale");
 textdomain($domain);
 
-function changeLanguage($lang, $f3) {
-    $_SESSION['LANGUAGE'] = $lang;
-    setcookie("LANGUAGE", $lang, strtotime('+1 year'));
-    putenv("LANGUAGE=$lang");
-    $f3->set('LANGUAGE', $lang);
-}
-
 $f3->set('TRANSLATION_LANGUAGE', _("en"));
 $f3->set('DIRECTION_LANGUAGE', 'ltr');
 if($f3->get('TRANSLATION_LANGUAGE') == "ar") {
@@ -474,6 +471,23 @@ function getCommit() {
     return substr($commit, 0, 7);
 }
 
+function selectLanguage($lang, $f3, $putCookie = false) {
+    $langSupported = null;
+    foreach(explode(',', $lang) as $l) {
+        if(array_key_exists($l, $f3->get('SUPPORTED_LANGUAGES'))) {
+            $langSupported = $l;
+            break;
+        }
+    }
+    if(!$langSupported) {
+        return null;
+    }
+    if($putCookie) {
+        setcookie("LANGUAGE", $langSupported, strtotime('+1 year'));
+    }
+    putenv("LANGUAGE=$langSupported");
+}
+
 function convertPHPSizeToBytes($sSize)
 {
     $sSuffix = strtoupper(substr($sSize, -1));
diff --git a/templates/components/navtab.html.php b/templates/components/navtab.html.php
index c55dc80..25caab7 100644
--- a/templates/components/navtab.html.php
+++ b/templates/components/navtab.html.php
@@ -5,7 +5,7 @@
             <span class="d-md-none"><i class="bi bi-translate"></i></span>
         </button>
         <ul class="dropdown-menu" aria-labelledby="dropdownMenuButton1">
-            <?php foreach ($LANGUAGES as $key => $langue):?>
+            <?php foreach ($SUPPORTED_LANGUAGES as $key => $langue):?>
                 <li><a class="dropdown-item" href="?lang=<?php echo $key ?>"><?php echo $langue ?></a></li>
             <?php endforeach; ?>
         </ul>