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    Creation:2025-12-07Last update:2026-05-31

    Translate your React Router v7 (File-System Routes) website using Intlayer | Internationalization (i18n)

    This guide demonstrates how to integrate Intlayer for seamless internationalization in React Router v7 projects using file-system based routing (@react-router/fs-routes) with locale-aware routing, TypeScript support, and modern development practices.

    For client-side routing, refer to the Intlayer with React Router v7 guide.

    Table of Contents

    Why Intlayer over alternatives?

    Compared to main solutions like react-i18next or i18next, Intlayer is a solution that comes with integrated optimizations such as:

    Intlayer is optimized to work perfectly with React Router by offering locale-aware routing, middleware for locale detection, and all the features needed for scaling internationalization (i18n).

    Instead of loading massive JSON files into your pages, load only the necessary content. Intlayer helps reduce your bundle and page sizes by up to 50%.

    Scoping your application's content facilitates maintenance for large-scale applications. You can duplicate or delete a single feature folder without the mental burden of reviewing your entire content codebase. Additionally, Intlayer is fully typed to ensure your content's accuracy.

    Co-locating content reduces the context needed by Large Language Models (LLMs). Intlayer also comes with a suite of tools, such as a CLI to test for missing translations,LSP, MCP, and agent skills, to make the developer experience (DX) even smoother for AI agents.

    Use automation to translate in your CI/CD pipeline using the LLM of your choice at the cost of your AI provider. Intlayer also offers a compiler to automate content extraction, as well as a web platform to help translate in the background.

    Connecting massive JSON files to components can lead to performance and reactivity issues. Intlayer optimizes your content loading at build time.

    More than just an i18n solution, Intlayer provides an self-hosted visual editor and a full CMS to help you manage your multilingual content in real-time, making collaboration with translators, copywriters, and other team members seamless. Content can be stored locally and/or remotely.

    Step-by-Step Guide to Set Up Intlayer in a React Router v7 Application with File-System Routes

    www.youtube.com

    See Application Template on GitHub.

    1. Install Dependencies

      Install the necessary packages using your preferred package manager:

      bash
      npm install intlayer react-intlayernpm install vite-intlayer --save-devnpm install @react-router/fs-routes --save-devnpx intlayer init

      • intlayer

        The core package that provides internationalization tools for configuration management, translation, content declaration, transpilation, and CLI commands.

      • react-intlayer The package that integrates Intlayer with React application. It provides context providers and hooks for React internationalization.

      • vite-intlayer Includes the Vite plugin for integrating Intlayer with the Vite bundler, as well as middleware for detecting the user's preferred locale, managing cookies, and handling URL redirection.

      • @react-router/fs-routes The package that enables file-system based routing for React Router v7.

    2. Configuration of your project

      Create a config file to configure the languages of your application:

      intlayer.config.ts
      import { type IntlayerConfig, Locales } from "intlayer";

const config: IntlayerConfig = {
  internationalization: {
    defaultLocale: Locales.ENGLISH,
    locales: [Locales.ENGLISH, Locales.FRENCH, Locales.SPANISH],
  },
};

export default config;
      Through this configuration file, you can set up localized URLs, middleware redirection, cookie names, the location and extension of your content declarations, disable Intlayer logs in the console, and more. For a complete list of available parameters, refer to the configuration documentation.

    3. Integrate Intlayer in Your Vite Configuration

      Add the intlayer plugin into your configuration:

      vite.config.ts
      import { reactRouter } from "@react-router/dev/vite";import { defineConfig } from "vite";import { intlayer } from "vite-intlayer";export default defineConfig({  plugins: [reactRouter(), intlayer()],});
      The intlayer() Vite plugin is used to integrate Intlayer with Vite. It ensures the building of content declaration files and monitors them in development mode. It defines Intlayer environment variables within the Vite application. Additionally, it provides aliases to optimize performance.

    4. Configure React Router v7 File-System Routes

      Set up your routing configuration to use file-system based routes with flatRoutes:

      app/routes.ts
      import type { RouteConfig } from "@react-router/dev/routes";import { flatRoutes } from "@react-router/fs-routes";import { configuration } from "intlayer";const routes: RouteConfig = flatRoutes({  // Ignore content declaration files from being treated as routes  ignoredRouteFiles: configuration.content.fileExtensions.map(    (fileExtension) => `**/*${fileExtension}`  ),});export default routes;
      The flatRoutes function from @react-router/fs-routes enables file-system based routing, where the file structure in the routes/ directory determines your application's routes. The ignoredRouteFiles option ensures that Intlayer content declaration files (.content.ts, etc.) are not treated as route files.

    5. Create Route Files with File-System Conventions

      With file-system routing, you use a flat naming convention where dots (.) represent path segments and parentheses () denote optional segments.

      Create the following files in your app/routes/ directory:

      File Structure

      bash
      app/├── root.tsx                         # Layout wrapper for locale routes└──routes/    ├── ($locale)._index.tsx         # Home page (/, /es, etc.)    ├── ($locale)._index.content.ts  # Home page content    ├── ($locale).about.tsx          # About page (/about, /es/about, etc.)    └── ($locale).about.content.ts   # About page content

      The naming conventions:

      • ($locale) - Optional dynamic segment for the locale parameter
      • _layout - Layout route that wraps child routes
      • _index - Index route (renders at the parent path)
      • . (dot) - Separates path segments (e.g., ($locale).about → /:locale?/about)

      Layout Component

      app/root.tsx
      import { getLocaleFromPath } from "intlayer";import { IntlayerProvider } from "react-intlayer";import {  isRouteErrorResponse,  Meta,  Outlet,  Scripts,  ScrollRestoration,  useLoaderData,} from "react-router";import type { Route } from "./+types/root";import "./app.css";// ... Unchanged App, links and ErrorBoundary codeexport async function loader({ request }: Route.LoaderArgs) {  const locale = getLocaleFromPath(request.url);  return { locale };}export function Layout({  children,}: { children: React.ReactNode } & Route.ComponentProps) {  const data = useLoaderData<typeof loader>();  const { locale } = data ?? {};  return (    <html lang={locale}>      <head>        <meta charSet="utf-8" />        <meta content="width=device-width, initial-scale=1" name="viewport" />        <Meta />        <Links />      </head>      <body>        <IntlayerProvider locale={locale}>{children}</IntlayerProvider>        <ScrollRestoration />        <Scripts />      </body>    </html>  );}

      Index Page

      app/routes/($locale)._index.tsx
      import { getIntlayer, validatePrefix } from "intlayer";import { useIntlayer } from "react-intlayer";import { data } from "react-router";import { LocaleSwitcher } from "~/components/locale-switcher";import { Navbar } from "~/components/navbar";import type { Route } from "./+types/($locale)._index";export const loader = ({ params }: Route.LoaderArgs) => {  const { locale } = params;  const { isValid } = validatePrefix(locale);  if (!isValid) {    throw data("Locale not supported", { status: 404 });  }};export const meta: Route.MetaFunction = ({ params }) => {  const content = getIntlayer("page", params.locale);  return [    { title: content.title },    { content: content.description, name: "description" },  ];};export default function Page() {  const { title, description, aboutLink } = useIntlayer("page");  return (    <div>      <h1>{title}</h1>      <p>{description}</p>      <nav>        <LocalizedLink to="/about">{aboutLink}</LocalizedLink>      </nav>    </div>  );}

      About Page

      app/routes/($locale).about.tsx
      import { getIntlayer, validatePrefix } from "intlayer";import { useIntlayer } from "react-intlayer";import { data } from "react-router";import { LocaleSwitcher } from "~/components/locale-switcher";import { Navbar } from "~/components/navbar";import type { Route } from "./+types/($locale).about";export const loader = ({ params }: Route.LoaderArgs) => {  const { locale } = params;  const { isValid } = validatePrefix(locale);  if (!isValid) {    throw data("Locale not supported", { status: 404 });  }};export const meta: Route.MetaFunction = ({ params }) => {  const content = getIntlayer("about", params.locale);  return [    { title: content.title },    { content: content.description, name: "description" },  ];};export default function AboutPage() {  const { title, content, homeLink } = useIntlayer("about");  return (    <div>      <h1>{title}</h1>      <p>{content}</p>      <nav>        <LocalizedLink to="/">{homeLink}</LocalizedLink>      </nav>    </div>  );}

    6. Declare Your Content

      Create and manage your content declarations to store translations. Place content files alongside your route files:

      app/routes/($locale)._index.content.ts
      import { t, type Dictionary } from "intlayer";const pageContent = {  key: "page",  content: {    title: t({      en: "Welcome to React Router v7 + Intlayer",      es: "Bienvenido a React Router v7 + Intlayer",      fr: "Bienvenue sur React Router v7 + Intlayer",    }),    description: t({      en: "Build multilingual applications with ease using React Router v7 and Intlayer.",      es: "Cree aplicaciones multilingües fácilmente usando React Router v7 y Intlayer.",      fr: "Créez des applications multilingues facilement avec React Router v7 et Intlayer.",    }),    aboutLink: t({      en: "Learn About Us",      es: "Aprender Sobre Nosotros",      fr: "En savoir plus sur nous",    }),  },} satisfies Dictionary;export default pageContent;
      app/routes/($locale).about.content.ts
      import { t, type Dictionary } from "intlayer";const aboutContent = {  key: "about",  content: {    title: t({      en: "About Us",      es: "Sobre Nosotros",      fr: "À propos de nous",    }),    content: t({      en: "This is the about page content.",      es: "Este es el contenido de la página de información.",      fr: "Ceci est le contenu de la page à propos.",    }),    homeLink: t({      en: "Home",      es: "Inicio",      fr: "Accueil",    }),  },} satisfies Dictionary;export default aboutContent;
      Your content declarations can be defined anywhere in your application as soon they are included into the contentDir directory (by default, ./app). And match the content declaration file extension (by default, .content.{json,ts,tsx,js,jsx,mjs,cjs,md,mdx,yaml,yml}).
      For more details, refer to the content declaration documentation.
      If your app already exists, you can use the Intlayer Compiler, as well as the extract command, to transform thousands of components in a second.

    7. Create Locale-Aware Components

      Create a LocalizedLink component for locale-aware navigation:

      app/components/localized-link.tsx
      import type { FC } from "react";import { getLocalizedUrl, type LocalesValues } from "intlayer";import { useLocale } from "react-intlayer";import { Link, type LinkProps, type To } from "react-router";const isExternalLink = (to: string) => /^(https?:)?\/\//.test(to);export const locacalizeTo = (to: To, locale: LocalesValues): To => {  if (typeof to === "string") {    if (isExternalLink(to)) {      return to;    }    return getLocalizedUrl(to, locale);  }  if (isExternalLink(to.pathname ?? "")) {    return to;  }  return {    ...to,    pathname: getLocalizedUrl(to.pathname ?? "", locale),  };};export const LocalizedLink: FC<LinkProps> = (props) => {  const { locale } = useLocale();  return <Link {...props} to={locacalizeTo(props.to, locale)} />;};

      In the case you want to navigate to the localized routes, you can use the useLocalizedNavigate hook:

      app/hooks/useLocalizedNavigate.ts
      import { useLocale } from "react-intlayer";import { type NavigateOptions, type To, useNavigate } from "react-router";import { locacalizeTo } from "~/components/localized-link";export const useLocalizedNavigate = () => {  const navigate = useNavigate();  const { locale } = useLocale();  const localizedNavigate = (to: To, options?: NavigateOptions) => {    const localedTo = locacalizeTo(to, locale);    navigate(localedTo, options);  };  return localizedNavigate;};

    8. Create a Locale Switcher Component

      Create a component to allow users to change languages:

      app/components/locale-switcher.tsx
      import type { FC } from "react";import {  getHTMLTextDir,  getLocaleName,  getLocalizedUrl,  getPathWithoutLocale,  Locales,} from "intlayer";import { useIntlayer, useLocale } from "react-intlayer";import { Link, useLocation } from "react-router";export const LocaleSwitcher: FC = () => {  const { localeSwitcherLabel } = useIntlayer("locale-switcher");  const { pathname } = useLocation();  const { availableLocales, locale } = useLocale();  const pathWithoutLocale = getPathWithoutLocale(pathname);  return (    <ol>      {availableLocales.map((localeItem) => (        <li key={localeItem}>          <Link            aria-current={localeItem === locale ? "page" : undefined}            aria-label={`${localeSwitcherLabel.value} ${getLocaleName(localeItem)}`}            reloadDocument // Reload the page to apply the new locale            to={getLocalizedUrl(pathWithoutLocale, localeItem)}          >            <span>              {/* Locale - e.g. FR */}              {localeItem}            </span>            <span>              {/* Language in its own Locale - e.g. Français */}              {getLocaleName(localeItem, locale)}            </span>            <span dir={getHTMLTextDir(localeItem)} lang={localeItem}>              {/* Language in current Locale - e.g. Francés with current locale set to Locales.SPANISH */}              {getLocaleName(localeItem)}            </span>            <span dir="ltr" lang={Locales.ENGLISH}>              {/* Language in English - e.g. French */}              {getLocaleName(localeItem, Locales.ENGLISH)}            </span>          </Link>        </li>      ))}    </ol>  );};
      To Learn more about the useLocale hook, refer to the documentation.

    9. Add HTML Attributes Management

      Create a hook to manage HTML lang and dir attributes:

      app/hooks/useI18nHTMLAttributes.tsx
      import { getHTMLTextDir } from "intlayer";import { useEffect } from "react";import { useLocale } from "react-intlayer";export const useI18nHTMLAttributes = () => {  const { locale } = useLocale();  useEffect(() => {    document.documentElement.lang = locale;    document.documentElement.dir = getHTMLTextDir(locale);  }, [locale]);};

      This hook is already used in the layout component (($locale)._layout.tsx) shown in Step 5.

    10. Add middleware

      You can also use the intlayerProxy to add server-side routing to your application. This plugin will automatically detect the current locale based on the URL and set the appropriate locale cookie. If no locale is specified, the plugin will determine the most appropriate locale based on the user's browser language preferences. If no locale is detected, it will redirect to the default locale.

      Note that to use the intlayerProxy in production, you need to switch the vite-intlayer package from devDependencies to dependencies.
      vite.config.ts
      import { reactRouter } from "@react-router/dev/vite";import { defineConfig } from "vite";import { intlayer, intlayerProxy } from "vite-intlayer";export default defineConfig({  plugins: [    intlayerProxy(), // should be placed first    reactRouter(),    intlayer(),  ],});

    11. Extract the content of your components

      Optional

      If you have an existing codebase, transforming thousands of files can be time-consuming.

      To ease this process, Intlayer propose a compiler / extractor to transform your components and extract the content.

      To set it up, you can add a compiler section in your intlayer.config.ts file:

      intlayer.config.ts
      import { type IntlayerConfig } from "intlayer";

const config: IntlayerConfig = {
  // ... Rest of your config
  compiler: {
    /**
     * Indicates if the compiler should be enabled.
     */
    enabled: true,

    /**
     * Defines the output files path
     */
    output: ({ fileName, extension }) => `./${fileName}${extension}`,

    /**
     * Indicates if the components should be saved after being transformed.
     *
     * - If `true`, the compiler will rewrite the component file in the disk. So the transformation will be permanent, and the compiler will skip the transformation for the next process. That way, the compiler can transform the app, and then it can be removed.
     *
     * - If `false`, the compiler will inject the `useIntlayer()` function call into the code in the build output only, and keep the base codebase intact. The transformation will be done only in memory.
     */
    saveComponents: false,

    /**
     * Dictionary key prefix
     */
    dictionaryKeyPrefix: "",
  },
};

export default config;

      Run the extractor to transform your components and extract the content

      bash
      npx intlayer extract

    Configure TypeScript

    Intlayer uses module augmentation to get benefits of TypeScript and make your codebase stronger.

    Ensure your TypeScript configuration includes the autogenerated types:

    tsconfig.json
    {  // ... your existing configurations  include: [    // ... your existing includes    ".intlayer/**/*.ts", // Include the auto-generated types  ],}

    Git Configuration

    It is recommended to ignore the files generated by Intlayer. This allows you to avoid committing them to your Git repository.

    To do this, you can add the following instructions to your .gitignore file:

    .gitignore
    # Ignore the files generated by Intlayer.intlayer

    VS Code Extension

    To improve your development experience with Intlayer, you can install the official Intlayer VS Code Extension.

    Install from the VS Code Marketplace

    This extension provides:

    • Autocompletion for translation keys.
    • Real-time error detection for missing translations.
    • Inline previews of translated content.
    • Quick actions to easily create and update translations.

    For more details on how to use the extension, refer to the Intlayer VS Code Extension documentation.

    Go Further

    To go further, you can implement the visual editor or externalize your content using the CMS.

    Documentation References

    This comprehensive guide provides everything you need to integrate Intlayer with React Router v7 using file-system based routing for a fully internationalized application with locale-aware routing and TypeScript support.

    React Router v7Compiler