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.

Table of Contents

What is Intlayer?

Intlayer is an innovative, open-source internationalization (i18n) library designed to simplify multilingual support in modern web applications.

With Intlayer, you can:

• Easily manage translations using declarative dictionaries at the component level.
• Dynamically localize metadata, routes, and content.
• Ensure TypeScript support with autogenerated types, improving autocompletion and error detection.
• Benefit from advanced features, like dynamic locale detection and switching.
• Enable locale-aware routing with React Router v7's file-system based routing system.

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

See Application Template on GitHub.

Step 1: Install Dependencies

Install the necessary packages using your preferred package manager:

npm install intlayer react-intlayernpm install vite-intlayer --save-devnpm install @react-router/fs-routes --save-dev

• 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.

Step 2: Configuration of your project

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

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.

Step 3: Integrate Intlayer in Your Vite Configuration

Add the intlayer plugin into your configuration:

import { reactRouter } from "@react-router/dev/vite";import { defineConfig } from "vite";import { intlayer } from "vite-intlayer";import tsconfigPaths from "vite-tsconfig-paths";export default defineConfig({  plugins: [reactRouter(), tsconfigPaths(), 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.

Step 4: Configure React Router v7 File-System Routes

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

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.

Step 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

app/routes/├── ($locale)._layout.tsx        # Layout wrapper for locale routes├── ($locale)._index.tsx         # Home page (/:locale?)├── ($locale)._index.content.ts  # Home page content├── ($locale).about.tsx          # About page (/:locale?/about)└── ($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

import { IntlayerProvider } from "react-intlayer";import { Outlet } from "react-router";import { useI18nHTMLAttributes } from "~/hooks/useI18nHTMLAttributes";import type { Route } from "./+types/($locale)._layout";export default function RootLayout({ params }: Route.ComponentProps) {  useI18nHTMLAttributes();  const { locale } = params;  return (    <IntlayerProvider locale={locale}>      <Outlet />    </IntlayerProvider>  );}

Index Page

import { useIntlayer } from "react-intlayer";import { LocalizedLink } from "~/components/localized-link";import type { Route } from "./+types/($locale)._index";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

import { useIntlayer } from "react-intlayer";import { LocalizedLink } from "~/components/localized-link";import type { Route } from "./+types/($locale).about";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>  );}

Step 6: Declare Your Content

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

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;

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,mjx,cjs,cjx}).

For more details, refer to the content declaration documentation.

Step 7: Create Locale-Aware Components

Create a LocalizedLink component for locale-aware navigation:

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:

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;};

Step 8: Create a Locale Switcher Component

Create a component to allow users to change languages:

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.

Step 9: Add HTML Attributes Management (Optional)

Create a hook to manage HTML lang and dir attributes:

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.

Step 10: Add middleware (Optional)

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.

import { reactRouter } from "@react-router/dev/vite";import { defineConfig } from "vite";import { intlayer, intlayerProxy } from "vite-intlayer";import tsconfigPaths from "vite-tsconfig-paths";export default defineConfig({  plugins: [reactRouter(), tsconfigPaths(), intlayer(), intlayerProxy()],});

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.