diff --git a/site/src/i18n/en.json b/site/src/i18n/en.json
new file mode 100644
index 0000000..45197fb
--- /dev/null
+++ b/site/src/i18n/en.json
@@ -0,0 +1,34 @@
+{
+  "nav.home": "Home",
+  "nav.install": "Install",
+  "nav.manual": "User manual",
+  "nav.github": "GitHub",
+  "hero.tabs": "termscp — {host} (sftp) connected",
+  "hero.local": "/home/veeso (local)",
+  "hero.remote": "/var/www (remote)",
+  "hero.status": "↹ switch · ↑↓ move · ↵ open · SPACE transfer",
+  "hero.title": "The dual-pane explorer for your terminal",
+  "hero.subtitle": "Local left, remote right. Transfer, sync, edit — never leave the keyboard.",
+  "hero.kicker": "// terminal file transfer",
+  "cta.install": "Install termscp →",
+  "cta.manual": "User manual",
+  "features.heading": "Why termscp",
+  "features.handy.title": "Handy UI",
+  "features.handy.body": "Explore and operate on the remote and local file system with a handy UI.",
+  "features.cross.title": "Cross platform",
+  "features.cross.body": "Runs on Windows, macOS, Linux and BSD.",
+  "features.custom.title": "Customizable",
+  "features.custom.body": "Customize the explorer, the text editor and default options.",
+  "features.bookmarks.title": "Bookmarks",
+  "features.bookmarks.body": "Connect to favourite hosts via bookmarks and recent connections.",
+  "features.security.title": "Security first",
+  "features.security.body": "Store passwords in your operating system key vault.",
+  "features.performance.title": "Eye on performance",
+  "features.performance.body": "Built with an eye on performance to keep CPU usage low.",
+  "protocols.heading": "Speaks every protocol",
+  "install.heading": "Install termscp",
+  "install.subtitle": "Pick your platform. One command and you're in.",
+  "footer.support": "Support me",
+  "footer.rights": "Released under the MIT license.",
+  "lang.label": "Language"
+}
diff --git a/site/src/i18n/es.json b/site/src/i18n/es.json
new file mode 100644
index 0000000..4ecbd76
--- /dev/null
+++ b/site/src/i18n/es.json
@@ -0,0 +1,34 @@
+{
+  "nav.home": "Inicio",
+  "nav.install": "Instalar",
+  "nav.manual": "Manual de usuario",
+  "nav.github": "GitHub",
+  "hero.tabs": "termscp — {host} (sftp) conectado",
+  "hero.local": "/home/veeso (local)",
+  "hero.remote": "/var/www (remoto)",
+  "hero.status": "↹ cambiar · ↑↓ mover · ↵ abrir · ESPACIO transferir",
+  "hero.title": "El explorador de doble panel para tu terminal",
+  "hero.subtitle": "Local a la izquierda, remoto a la derecha. Transfiere, sincroniza, edita — sin soltar el teclado.",
+  "hero.kicker": "// transferencia de archivos en terminal",
+  "cta.install": "Instalar termscp →",
+  "cta.manual": "Manual de usuario",
+  "features.heading": "Por qué termscp",
+  "features.handy.title": "Interfaz práctica",
+  "features.handy.body": "Explora y opera en el sistema de archivos remoto y local con una interfaz práctica.",
+  "features.cross.title": "Multiplataforma",
+  "features.cross.body": "Funciona en Windows, macOS, Linux y BSD.",
+  "features.custom.title": "Personalizable",
+  "features.custom.body": "Personaliza el explorador, el editor de texto y las opciones predeterminadas.",
+  "features.bookmarks.title": "Marcadores",
+  "features.bookmarks.body": "Conéctate a tus hosts favoritos mediante marcadores y conexiones recientes.",
+  "features.security.title": "Seguridad primero",
+  "features.security.body": "Guarda tus contraseñas en la bóveda de claves de tu sistema operativo.",
+  "features.performance.title": "Ojo en el rendimiento",
+  "features.performance.body": "Desarrollado teniendo en cuenta el rendimiento para mantener bajo el uso de CPU.",
+  "protocols.heading": "Habla todos los protocolos",
+  "install.heading": "Instalar termscp",
+  "install.subtitle": "Elige tu plataforma. Un comando y listo.",
+  "footer.support": "Apóyame",
+  "footer.rights": "Publicado bajo la licencia MIT.",
+  "lang.label": "Idioma"
+}
diff --git a/site/src/i18n/fr.json b/site/src/i18n/fr.json
new file mode 100644
index 0000000..eb24478
--- /dev/null
+++ b/site/src/i18n/fr.json
@@ -0,0 +1,33 @@
+{
+  "nav.home": "Accueil",
+  "nav.install": "Installer",
+  "nav.github": "GitHub",
+  "hero.tabs": "termscp — {host} (sftp) connecté",
+  "hero.local": "/home/veeso (local)",
+  "hero.remote": "/var/www (distant)",
+  "hero.status": "↹ basculer · ↑↓ déplacer · ↵ ouvrir · ESPACE transférer",
+  "hero.title": "L'explorateur à deux panneaux pour votre terminal",
+  "hero.subtitle": "Local à gauche, distant à droite. Transférez, synchronisez, éditez — sans quitter le clavier.",
+  "hero.kicker": "// transfert de fichiers en terminal",
+  "cta.install": "Installer termscp →",
+  "cta.manual": "Manuel d'utilisateur",
+  "features.heading": "Pourquoi termscp",
+  "features.handy.title": "Interface pratique",
+  "features.handy.body": "Explorez et utilisez le système de fichiers distant et local avec une interface pratique.",
+  "features.cross.title": "Multi-plateforme",
+  "features.cross.body": "Fonctionne sur Windows, macOS, Linux et BSD.",
+  "features.custom.title": "Personnalisable",
+  "features.custom.body": "Personnalisez l'explorateur, l'éditeur de texte et les options par défaut.",
+  "features.bookmarks.title": "Signets",
+  "features.bookmarks.body": "Connectez-vous à vos hôtes préférés via des signets et des connexions récentes.",
+  "features.security.title": "Sécurité avant tout",
+  "features.security.body": "Enregistrez vos mots de passe dans le coffre-fort de votre système.",
+  "features.performance.title": "Regard sur les performances",
+  "features.performance.body": "Développé en gardant un œil sur les performances pour éviter une utilisation élevée du processeur.",
+  "protocols.heading": "Parle tous les protocoles",
+  "install.heading": "Installer termscp",
+  "install.subtitle": "Choisissez votre plateforme. Une commande et c'est parti.",
+  "footer.support": "Me soutenir",
+  "footer.rights": "Publié sous licence MIT.",
+  "lang.label": "Langue"
+}
diff --git a/site/src/i18n/it.json b/site/src/i18n/it.json
new file mode 100644
index 0000000..c4e1f0c
--- /dev/null
+++ b/site/src/i18n/it.json
@@ -0,0 +1,34 @@
+{
+  "nav.home": "Home",
+  "nav.install": "Installa",
+  "nav.manual": "Manuale utente",
+  "nav.github": "GitHub",
+  "hero.tabs": "termscp — {host} (sftp) connesso",
+  "hero.local": "/home/veeso (locale)",
+  "hero.remote": "/var/www (remoto)",
+  "hero.status": "↹ cambia · ↑↓ muovi · ↵ apri · SPAZIO trasferisci",
+  "hero.title": "L'explorer a doppio pannello per il tuo terminale",
+  "hero.subtitle": "Locale a sinistra, remoto a destra. Trasferisci, sincronizza, modifica — senza mai lasciare la tastiera.",
+  "hero.kicker": "// file transfer da terminale",
+  "cta.install": "Installa termscp →",
+  "cta.manual": "Manuale utente",
+  "features.heading": "Perché termscp",
+  "features.handy.title": "UI ergonomica",
+  "features.handy.body": "Naviga e lavora sul file system remoto e locale attraverso una UI di facile utilizzo.",
+  "features.cross.title": "Multi piattaforma",
+  "features.cross.body": "Gira su Windows, macOS, Linux e BSD.",
+  "features.custom.title": "Personalizzabile",
+  "features.custom.body": "Personalizza l'explorer, l'editor di testo e le opzioni predefinite.",
+  "features.bookmarks.title": "Preferiti",
+  "features.bookmarks.body": "Connettiti agli host preferiti tramite preferiti e connessioni recenti.",
+  "features.security.title": "Sicurezza in prima classe",
+  "features.security.body": "Salva le password nel vault del tuo sistema operativo.",
+  "features.performance.title": "Focus sulle performance",
+  "features.performance.body": "Sviluppato con un occhio alle performance per mantenere basso l'uso della CPU.",
+  "protocols.heading": "Parla ogni protocollo",
+  "install.heading": "Installa termscp",
+  "install.subtitle": "Scegli la tua piattaforma. Un comando e sei dentro.",
+  "footer.support": "Supportami",
+  "footer.rights": "Rilasciato sotto licenza MIT.",
+  "lang.label": "Lingua"
+}
diff --git a/site/src/i18n/ui.test.ts b/site/src/i18n/ui.test.ts
new file mode 100644
index 0000000..1836602
--- /dev/null
+++ b/site/src/i18n/ui.test.ts
@@ -0,0 +1,29 @@
+import { describe, expect, it } from "vitest";
+import { useTranslations, locales, defaultLocale } from "./ui";
+
+describe("i18n", () => {
+  it("exposes the five supported locales with en default", () => {
+    expect(locales).toEqual(["en", "zh-CN", "it", "fr", "es"]);
+    expect(defaultLocale).toBe("en");
+  });
+
+  it("resolves a key in the requested locale", () => {
+    const t = useTranslations("it");
+    expect(t("nav.install")).toBe("Installa");
+  });
+
+  it("falls back to en when a key is missing in the locale", () => {
+    const t = useTranslations("fr");
+    expect(t("nav.manual")).toBe("User manual");
+  });
+
+  it("returns the key itself when missing everywhere", () => {
+    const t = useTranslations("en");
+    expect(t("does.not.exist")).toBe("does.not.exist");
+  });
+
+  it("interpolates {vars}", () => {
+    const t = useTranslations("en");
+    expect(t("hero.tabs", { host: "1.2.3.4" })).toContain("1.2.3.4");
+  });
+});
diff --git a/site/src/i18n/ui.ts b/site/src/i18n/ui.ts
new file mode 100644
index 0000000..9c3219b
--- /dev/null
+++ b/site/src/i18n/ui.ts
@@ -0,0 +1,35 @@
+import en from "./en.json";
+import zhCN from "./zh-CN.json";
+import it from "./it.json";
+import fr from "./fr.json";
+import es from "./es.json";
+
+export const locales = ["en", "zh-CN", "it", "fr", "es"] as const;
+export type Locale = (typeof locales)[number];
+export const defaultLocale: Locale = "en";
+
+const dictionaries: Record<Locale, Record<string, string>> = {
+  en: en as Record<string, string>,
+  "zh-CN": zhCN as Record<string, string>,
+  it: it as Record<string, string>,
+  fr: fr as Record<string, string>,
+  es: es as Record<string, string>,
+};
+
+export function isLocale(value: string): value is Locale {
+  return (locales as readonly string[]).includes(value);
+}
+
+/** Resolve a translator for `locale`, falling back to en, then to the key. */
+export function useTranslations(locale: Locale) {
+  const dict = dictionaries[locale] ?? dictionaries[defaultLocale];
+  return (key: string, vars?: Record<string, string>): string => {
+    let value = dict[key] ?? dictionaries[defaultLocale][key] ?? key;
+    if (vars) {
+      for (const [k, v] of Object.entries(vars)) {
+        value = value.replaceAll(`{${k}}`, v);
+      }
+    }
+    return value;
+  };
+}
diff --git a/site/src/i18n/zh-CN.json b/site/src/i18n/zh-CN.json
new file mode 100644
index 0000000..9145362
--- /dev/null
+++ b/site/src/i18n/zh-CN.json
@@ -0,0 +1,34 @@
+{
+  "nav.home": "主页",
+  "nav.install": "安装",
+  "nav.manual": "用户手册",
+  "nav.github": "GitHub",
+  "hero.tabs": "termscp — {host} (sftp) 已连接",
+  "hero.local": "/home/veeso （本地）",
+  "hero.remote": "/var/www （远程）",
+  "hero.status": "↹ 切换 · ↑↓ 移动 · ↵ 打开 · 空格 传输",
+  "hero.title": "为你的终端打造的双栏文件浏览器",
+  "hero.subtitle": "左边本地，右边远程。传输、同步、编辑 — 始终不离键盘。",
+  "hero.kicker": "// 终端文件传输",
+  "cta.install": "安装 termscp →",
+  "cta.manual": "用户手册",
+  "features.heading": "为什么选择 termscp",
+  "features.handy.title": "方便的用户界面",
+  "features.handy.body": "使用方便的 UI 在远程和本地文件系统上探索和操作。",
+  "features.cross.title": "跨平台",
+  "features.cross.body": "在 Windows、macOS、Linux 和 BSD 上运行。",
+  "features.custom.title": "可定制",
+  "features.custom.body": "自定义文件浏览器、文本编辑器和默认选项。",
+  "features.bookmarks.title": "书签",
+  "features.bookmarks.body": "通过书签和最近的连接连接到你最喜欢的主机。",
+  "features.security.title": "安全第一",
+  "features.security.body": "将你的密码保存到操作系统的密钥保管库中。",
+  "features.performance.title": "关注性能",
+  "features.performance.body": "在开发时关注性能，以保持较低的 CPU 使用率。",
+  "protocols.heading": "支持各种协议",
+  "install.heading": "安装 termscp",
+  "install.subtitle": "选择你的平台。一条命令即可上手。",
+  "footer.support": "支持我",
+  "footer.rights": "基于 MIT 许可证发布。",
+  "lang.label": "语言"
+}
diff --git a/site/tsconfig.json b/site/tsconfig.json
index 8bf91d3..0645975 100644
--- a/site/tsconfig.json
+++ b/site/tsconfig.json
@@ -1,5 +1,8 @@
 {
   "extends": "astro/tsconfigs/strict",
+  "compilerOptions": {
+    "resolveJsonModule": true
+  },
   "include": [".astro/types.d.ts", "**/*"],
   "exclude": ["dist"]
 }
diff --git a/site/vitest.config.ts b/site/vitest.config.ts
new file mode 100644
index 0000000..77318ed
--- /dev/null
+++ b/site/vitest.config.ts
@@ -0,0 +1,5 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: { include: ["src/**/*.test.ts", "scripts/**/*.test.ts"] },
+});