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:

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

VideoCodeDemo

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ide.intlayer.org

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intlayer-react-router-v7-fs-routes.vercel.app

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See Application Template on GitHub.

1. 1

   Install Dependencies

   Install the necessary packages using your preferred package manager:

   bash

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   npm install intlayer react-intlayer
   npm install vite-intlayer --save-dev
   npm install @react-router/fs-routes --save-dev
   npx 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. 2

   Configuration of your project

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

   intlayer.config.ts

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   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. 3

   Integrate Intlayer in Your Vite Configuration

   Add the intlayer plugin into your configuration:

   vite.config.ts

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   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. 4

   Configure React Router v7 File-System Routes

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

   app/routes.ts

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   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. 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

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   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

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   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 code
   
   export 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

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   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

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   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. 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

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   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

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   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. 7

   Create Locale-Aware Components

   Create a LocalizedLink component for locale-aware navigation:

   app/components/localized-link.tsx

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   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

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   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. 8

   Create a Locale Switcher Component

   Create a component to allow users to change languages:

   app/components/locale-switcher.tsx

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   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. 9

   Add HTML Attributes Management

   Create a hook to manage HTML lang and dir attributes:

   app/hooks/useI18nHTMLAttributes.tsx

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   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. 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.

    Since Intlayer v9, intlayerProxy() is bundled directly into the intlayer() plugin and enabled by default through the routing.enableProxy option (true by default). Registering it separately as shown below is now optional — it is kept for backward compatibility and for setups that need to control plugin order. Set routing.enableProxy: false to opt out. See the v9 release notes.

    vite.config.ts

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    import { reactRouter } from "@react-router/dev/vite";
    import { defineConfig } from "vite";
    import { intlayer } from "vite-intlayer";
    
    export default defineConfig({
      plugins: [
        reactRouter(),
    
        intlayer({
          proxy: {
            ignore: (req) => req.url?.startsWith("/api"),
          },
        }),
      ],
    });
    

11. 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

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    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;
    

    Extract commandBabel compiler

    Run the extractor to transform your components and extract the content

    bash

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    npx intlayer extract
    

    Since v9, the intlayerCompiler is included in the intlayer plugin. So you don't need to add it manually.

    Update your vite.config.ts to include the intlayerCompiler plugin:

    vite.config.ts

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    import { defineConfig } from "vite";
    import { intlayer, intlayerCompiler } from "vite-intlayer";
    
    export default defineConfig({
      plugins: [
        intlayer(),
        intlayerCompiler(), // Adds the compiler plugin
      ],
    });
    

    bash

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    npm run build # Or npm run dev
    

Configure TypeScript

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

Ensure your TypeScript configuration includes the autogenerated types:

{
  // ... 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:

# 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

• Intlayer Documentation
• React Router v7 Documentation
• React Router fs-routes Documentation
• useIntlayer hook
• useLocale hook
• Content Declaration
• Configuration

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.

Frequently Asked Questions