diff --git a/client/src/components/layout/Navbar.tsx b/client/src/components/layout/Navbar.tsx
index 7edc820..5020e73 100644
--- a/client/src/components/layout/Navbar.tsx
+++ b/client/src/components/layout/Navbar.tsx
@@ -10,6 +10,31 @@ import { cn } from '@/lib/utils';
 const LANGS = ['EN', 'PT', 'ES'] as const;
 type Lang = (typeof LANGS)[number];
 
+interface NavLinkProps {
+  to: string;
+  label: string;
+  active: boolean;
+}
+
+function NavLink({ to, label, active }: NavLinkProps) {
+  return (
+    <Link
+      to={to}
+      className={cn(
+        'relative h-8 px-2 sm:px-3 flex items-center text-sm font-medium rounded-md transition-colors whitespace-nowrap',
+        active
+          ? 'text-foreground bg-muted'
+          : 'text-muted-foreground hover:text-foreground hover:bg-muted/50',
+      )}
+    >
+      {label}
+      {active && (
+        <span className="absolute bottom-0 left-2 right-2 h-0.5 bg-primary rounded-full" />
+      )}
+    </Link>
+  );
+}
+
 export function Navbar() {
   const { isAuthenticated, user, clearAuth } = useAuthStore();
   const { theme, toggle } = useThemeStore();
@@ -20,7 +45,12 @@ export function Navbar() {
   const activeLang = inst.language.toUpperCase().slice(0, 2) as Lang;
 
   const handleLogout = async () => {
-    try { await api.post('/auth/logout'); } finally { clearAuth(); navigate('/'); }
+    try {
+      await api.post('/auth/logout');
+    } finally {
+      clearAuth();
+      navigate('/');
+    }
   };
 
   const switchLang = (lang: Lang) => {
@@ -28,65 +58,45 @@ export function Navbar() {
     localStorage.setItem('chesskernel-lang', lang.toLowerCase());
   };
 
-  const isActive = (to: string) => location.pathname === to || location.pathname.startsWith(to + '/');
+  const cycleLang = () => {
+    const next = LANGS[(LANGS.indexOf(activeLang) + 1) % LANGS.length];
+    switchLang(next);
+  };
+
+  const isActive = (to: string) =>
+    location.pathname === to || location.pathname.startsWith(to + '/');
 
   return (
     <nav className="sticky top-0 z-50 border-b border-border bg-card">
       {/*
-        3-column CSS grid with FIXED right column width (260px).
-        Nav text can change length freely without ever shifting the right section.
+        Layout rules that keep the bar stable across languages:
+        - left and right blocks are pinned by justify-between, so link text
+          growing never pushes the controls around
+        - auth buttons reserve the width of their longest translation via
+          ch-based minimums, so switching language never resizes them
+        - every control has a fixed height and shrink-0
       */}
-      <div
-        className="max-w-7xl mx-auto px-4 sm:px-6 h-14"
-        style={{ display: 'grid', gridTemplateColumns: '1fr auto 260px', alignItems: 'center', gap: '0' }}
-      >
-        {/* Left: logo + nav links */}
-        <div className="flex items-center gap-0.5">
+      <div className="max-w-7xl mx-auto px-3 sm:px-6 h-14 flex items-center justify-between gap-2">
+        {/* Left: logo + primary nav */}
+        <div className="flex items-center gap-0.5 min-w-0">
           <Link
             to="/"
-            className="flex items-center gap-1 font-black text-sm text-primary tracking-tight mr-4 shrink-0"
-          >
-            ♔ <span className="hidden sm:inline">ChessKernel</span>
-          </Link>
-
-          <Link
-            to="/play"
-            className={cn(
-              'relative h-8 px-3 flex items-center text-sm font-medium rounded-md transition-colors whitespace-nowrap',
-              isActive('/play')
-                ? 'text-foreground bg-muted'
-                : 'text-muted-foreground hover:text-foreground hover:bg-muted/50',
-            )}
+            className="flex items-center gap-1 font-black text-sm text-primary tracking-tight mr-2 sm:mr-4 shrink-0"
           >
-            {t('nav.play')}
-            {isActive('/play') && (
-              <span className="absolute bottom-0 left-2 right-2 h-0.5 bg-primary rounded-full" />
-            )}
+            ♔ <span className="hidden md:inline">ChessKernel</span>
           </Link>
-
-          <Link
+          <NavLink to="/play" label={t('nav.play')} active={isActive('/play')} />
+          <NavLink
             to="/leaderboard"
-            className={cn(
-              'relative h-8 px-3 flex items-center text-sm font-medium rounded-md transition-colors whitespace-nowrap',
-              isActive('/leaderboard')
-                ? 'text-foreground bg-muted'
-                : 'text-muted-foreground hover:text-foreground hover:bg-muted/50',
-            )}
-          >
-            {t('nav.leaderboard')}
-            {isActive('/leaderboard') && (
-              <span className="absolute bottom-0 left-2 right-2 h-0.5 bg-primary rounded-full" />
-            )}
-          </Link>
+            label={t('nav.leaderboard')}
+            active={isActive('/leaderboard')}
+          />
         </div>
 
-        {/* Center: spacer (flex-1 equivalent in grid) */}
-        <div />
-
-        {/* Right: fixed 260px — controls never shift */}
-        <div className="flex items-center justify-end gap-1.5">
-          {/* Language switcher — always 88px */}
-          <div className="flex items-center bg-muted rounded-lg p-0.5" style={{ width: 88 }}>
+        {/* Right: controls, all fixed-size */}
+        <div className="flex items-center gap-1 sm:gap-1.5 shrink-0">
+          {/* Language: segmented control on sm+, single cycle button on mobile */}
+          <div className="hidden sm:flex items-center bg-muted rounded-lg p-0.5 w-[88px] shrink-0">
             {LANGS.map((lang) => (
               <button
                 key={lang}
@@ -102,31 +112,37 @@ export function Navbar() {
               </button>
             ))}
           </div>
+          <button
+            onClick={cycleLang}
+            aria-label={t('nav.language')}
+            title={t('nav.language')}
+            className="sm:hidden w-9 h-8 flex items-center justify-center rounded-md bg-muted text-[11px] font-bold text-foreground shrink-0"
+          >
+            {activeLang}
+          </button>
 
-          {/* Theme toggle — always 32px */}
           <button
             onClick={toggle}
-            aria-label="Toggle theme"
+            aria-label={t('nav.theme')}
+            title={t('nav.theme')}
             className="w-8 h-8 flex items-center justify-center rounded-md text-muted-foreground hover:text-foreground hover:bg-muted transition-colors shrink-0"
           >
             {theme === 'dark' ? <Sun size={15} /> : <Moon size={15} />}
           </button>
 
-          <div className="w-px h-4 bg-border mx-0.5 shrink-0" />
+          <div className="hidden sm:block w-px h-4 bg-border mx-0.5 shrink-0" />
 
-          {/* Auth — always right-aligned inside fixed 260px column */}
           {isAuthenticated ? (
-            <div className="flex items-center gap-1">
+            <div className="flex items-center gap-1 shrink-0">
               <Link
                 to={`/user/${user?.username}`}
-                className="flex items-center gap-1.5 h-8 px-2 rounded-md text-sm font-medium text-muted-foreground hover:text-foreground hover:bg-muted transition-colors max-w-[100px]"
+                className="flex items-center gap-1.5 h-8 px-1.5 sm:px-2 rounded-md text-sm font-medium text-muted-foreground hover:text-foreground hover:bg-muted transition-colors max-w-[110px]"
               >
                 <div className="w-6 h-6 rounded-full bg-primary/15 text-primary flex items-center justify-center text-xs font-bold shrink-0">
                   {user?.username?.[0]?.toUpperCase()}
                 </div>
                 <span className="truncate hidden sm:inline">{user?.username}</span>
               </Link>
-              {/* Icon-only logout — zero width change across languages */}
               <button
                 onClick={handleLogout}
                 title={t('nav.logout')}
@@ -137,16 +153,18 @@ export function Navbar() {
               </button>
             </div>
           ) : (
-            <div className="flex items-center gap-1">
+            <div className="flex items-center gap-1 shrink-0">
+              {/* min-w reserves the longest translation ("Iniciar sesión" /
+                  "Registrarse"), so language switches never resize these */}
               <Link
                 to="/login"
-                className="h-8 px-3 flex items-center text-sm font-medium text-muted-foreground hover:text-foreground hover:bg-muted rounded-md transition-colors whitespace-nowrap"
+                className="hidden sm:flex h-8 px-2 min-w-[13ch] items-center justify-center text-sm font-medium text-muted-foreground hover:text-foreground hover:bg-muted rounded-md transition-colors whitespace-nowrap"
               >
                 {t('nav.login')}
               </Link>
               <Link
                 to="/register"
-                className="h-8 px-3 flex items-center bg-primary text-primary-foreground text-sm font-bold rounded-md hover:bg-primary/90 transition-colors whitespace-nowrap"
+                className="h-8 px-2.5 sm:px-3 sm:min-w-[11ch] flex items-center justify-center bg-primary text-primary-foreground text-sm font-bold rounded-md hover:bg-primary/90 transition-colors whitespace-nowrap"
               >
                 {t('nav.signUp')}
               </Link>
diff --git a/client/src/i18n/index.ts b/client/src/i18n/index.ts
index cabc612..f789727 100644
--- a/client/src/i18n/index.ts
+++ b/client/src/i18n/index.ts
@@ -14,4 +14,19 @@ i18n.use(initReactI18next).init({
   interpolation: { escapeValue: false },
 });
 
+/** Full BCP 47 tags for the html lang attribute. */
+const HTML_LANG: Record<string, string> = { en: 'en', pt: 'pt-BR', es: 'es' };
+
+/** Keeps tab title, meta description, and html lang in the active language. */
+function syncDocumentLanguage(language: string): void {
+  document.title = i18n.t('meta.title');
+  document
+    .querySelector('meta[name="description"]')
+    ?.setAttribute('content', i18n.t('meta.description'));
+  document.documentElement.lang = HTML_LANG[language] ?? language;
+}
+
+syncDocumentLanguage(lng);
+i18n.on('languageChanged', syncDocumentLanguage);
+
 export default i18n;
diff --git a/client/src/i18n/locales/en.json b/client/src/i18n/locales/en.json
index 2d0554e..7c50762 100644
--- a/client/src/i18n/locales/en.json
+++ b/client/src/i18n/locales/en.json
@@ -4,7 +4,9 @@
     "leaderboard": "Leaderboard",
     "login": "Log In",
     "signUp": "Sign Up",
-    "logout": "Log Out"
+    "logout": "Log Out",
+    "language": "Change language",
+    "theme": "Toggle theme"
   },
   "home": {
     "tagline": "Open Source · Free Forever",
@@ -15,11 +17,26 @@
     "featuresTitle": "Everything you need to play chess",
     "featuresSubtitle": "A full chess experience with no subscriptions, no ads, no tracking.",
     "features": {
-      "realtime":  { "title": "Real-time Play",   "desc": "Live games with instant moves. No delays, no lag." },
-      "bots":      { "title": "Play vs Stockfish", "desc": "Challenge the world's strongest engine at any difficulty." },
-      "analysis":  { "title": "Move Analysis",     "desc": "Automatic post-game review with move classifications." },
-      "ladder":    { "title": "Leaderboards",      "desc": "Separate ratings for bullet, blitz, rapid, and classical." },
-      "multilang": { "title": "Multilingual",      "desc": "Full support for English, Portuguese, and Spanish." }
+      "realtime": {
+        "title": "Real-time Play",
+        "desc": "Live games with instant moves. No delays, no lag."
+      },
+      "bots": {
+        "title": "Play vs Stockfish",
+        "desc": "Challenge the world's strongest engine at any difficulty."
+      },
+      "analysis": {
+        "title": "Move Analysis",
+        "desc": "Automatic post-game review with move classifications."
+      },
+      "ladder": {
+        "title": "Leaderboards",
+        "desc": "Separate ratings for bullet, blitz, rapid, and classical."
+      },
+      "multilang": {
+        "title": "Multilingual",
+        "desc": "Full support for English, Portuguese, and Spanish."
+      }
     }
   },
   "play": {
@@ -129,5 +146,9 @@
   "theme": {
     "light": "Light",
     "dark": "Dark"
+  },
+  "meta": {
+    "title": "ChessKernel: free, open-source chess platform",
+    "description": "Play chess online on your own terms: real-time multiplayer, Stockfish analysis, and Glicko-2 ratings. Free, open source, self-hostable, no ads or subscriptions."
   }
 }
diff --git a/client/src/i18n/locales/es.json b/client/src/i18n/locales/es.json
index 3ec49ae..ec2bdd2 100644
--- a/client/src/i18n/locales/es.json
+++ b/client/src/i18n/locales/es.json
@@ -4,7 +4,9 @@
     "leaderboard": "Clasificación",
     "login": "Iniciar sesión",
     "signUp": "Registrarse",
-    "logout": "Cerrar sesión"
+    "logout": "Cerrar sesión",
+    "language": "Cambiar idioma",
+    "theme": "Cambiar tema"
   },
   "home": {
     "tagline": "Código Abierto · Gratuito Para Siempre",
@@ -15,11 +17,26 @@
     "featuresTitle": "Todo lo que necesitas para jugar ajedrez",
     "featuresSubtitle": "Una experiencia completa sin suscripciones, sin anuncios, sin rastreo.",
     "features": {
-      "realtime":  { "title": "Juego en Vivo",      "desc": "Partidas en directo con movimientos instantáneos." },
-      "bots":      { "title": "vs Stockfish",        "desc": "Desafía al mejor motor de ajedrez en cualquier nivel." },
-      "analysis":  { "title": "Análisis de Jugadas", "desc": "Revisión automática con clasificación de jugadas." },
-      "ladder":    { "title": "Clasificación",       "desc": "Ratings separados para bullet, blitz, rapid y clásico." },
-      "multilang": { "title": "Multilingüe",         "desc": "Soporte completo para inglés, portugués y español." }
+      "realtime": {
+        "title": "Juego en Vivo",
+        "desc": "Partidas en directo con movimientos instantáneos."
+      },
+      "bots": {
+        "title": "vs Stockfish",
+        "desc": "Desafía al mejor motor de ajedrez en cualquier nivel."
+      },
+      "analysis": {
+        "title": "Análisis de Jugadas",
+        "desc": "Revisión automática con clasificación de jugadas."
+      },
+      "ladder": {
+        "title": "Clasificación",
+        "desc": "Ratings separados para bullet, blitz, rapid y clásico."
+      },
+      "multilang": {
+        "title": "Multilingüe",
+        "desc": "Soporte completo para inglés, portugués y español."
+      }
     }
   },
   "play": {
@@ -129,5 +146,9 @@
   "theme": {
     "light": "Claro",
     "dark": "Oscuro"
+  },
+  "meta": {
+    "title": "ChessKernel: plataforma de ajedrez gratuita y de código abierto",
+    "description": "Juega al ajedrez online a tu manera: multijugador en tiempo real, análisis con Stockfish y puntuaciones Glicko-2. Gratis, de código abierto y autoalojable, sin anuncios ni suscripciones."
   }
 }
diff --git a/client/src/i18n/locales/pt.json b/client/src/i18n/locales/pt.json
index 53d45e8..b4d154e 100644
--- a/client/src/i18n/locales/pt.json
+++ b/client/src/i18n/locales/pt.json
@@ -4,7 +4,9 @@
     "leaderboard": "Placar",
     "login": "Entrar",
     "signUp": "Cadastrar",
-    "logout": "Sair"
+    "logout": "Sair",
+    "language": "Mudar idioma",
+    "theme": "Alternar tema"
   },
   "home": {
     "tagline": "Código Aberto · Gratuito Para Sempre",
@@ -15,11 +17,26 @@
     "featuresTitle": "Tudo que você precisa para jogar xadrez",
     "featuresSubtitle": "Uma experiência completa sem assinaturas, sem anúncios, sem rastreamento.",
     "features": {
-      "realtime":  { "title": "Jogo em Tempo Real",  "desc": "Partidas ao vivo com lances instantâneos." },
-      "bots":      { "title": "vs Stockfish",         "desc": "Desafie o melhor motor de xadrez em qualquer nível." },
-      "analysis":  { "title": "Análise de Lances",    "desc": "Revisão automática com classificação de lances." },
-      "ladder":    { "title": "Classificação",        "desc": "Ratings separados para bullet, blitz, rapid e clássico." },
-      "multilang": { "title": "Multilíngue",          "desc": "Suporte completo para inglês, português e espanhol." }
+      "realtime": {
+        "title": "Jogo em Tempo Real",
+        "desc": "Partidas ao vivo com lances instantâneos."
+      },
+      "bots": {
+        "title": "vs Stockfish",
+        "desc": "Desafie o melhor motor de xadrez em qualquer nível."
+      },
+      "analysis": {
+        "title": "Análise de Lances",
+        "desc": "Revisão automática com classificação de lances."
+      },
+      "ladder": {
+        "title": "Classificação",
+        "desc": "Ratings separados para bullet, blitz, rapid e clássico."
+      },
+      "multilang": {
+        "title": "Multilíngue",
+        "desc": "Suporte completo para inglês, português e espanhol."
+      }
     }
   },
   "play": {
@@ -129,5 +146,9 @@
   "theme": {
     "light": "Claro",
     "dark": "Escuro"
+  },
+  "meta": {
+    "title": "ChessKernel: plataforma de xadrez gratuita e open source",
+    "description": "Jogue xadrez online do seu jeito: multiplayer em tempo real, análise com Stockfish e ratings Glicko-2. Gratuito, open source e auto-hospedável, sem anúncios ou assinaturas."
   }
 }