Getting Started Internationalizing (i18n) with Intlayer and Next.js using Page Router

What is Intlayer?

Intlayer is an innovative, open-source internationalization (i18n) library designed to simplify multilingual support in modern web applications. Intlayer seamlessly integrates with the latest Next.js framework, including its traditional Page Router.

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.

Intlayer is compatible with Next.js 12, 13, 14, and 15. If you are using Next.js App Router, refer to the App Router guide. For Next.js 15, follow this guide.

Step-by-Step Guide to Set Up Intlayer in a Next.js Application Using Page Router

Step 1: Install Dependencies

Install the necessary packages using your preferred package manager:

npm install intlayer next-intlayer

• intlayer

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

• next-intlayer

  The package that integrates Intlayer with Next.js. It provides context providers and hooks for Next.js internationalization. Additionally, it includes the Next.js plugin for integrating Intlayer with Webpack or Turbopack, as well as middleware for detecting the user's preferred locale, managing cookies, and handling URL redirection.

Step 2: Configure Your Project

Create a configuration file to define the languages supported by your application:

import { Locales, type IntlayerConfig } from "intlayer";const config: IntlayerConfig = {  internationalization: {    locales: [      Locales.ENGLISH,      Locales.FRENCH,      Locales.SPANISH,      // Add your other locales here    ],    defaultLocale: Locales.ENGLISH,  },};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 with Next.js Configuration

Modify your Next.js configuration to incorporate Intlayer:

import { withIntlayer } from "next-intlayer/server";/** @type {import('next').NextConfig} */const nextConfig = {  // Your existing Next.js configuration};export default withIntlayer(nextConfig);

The withIntlayer() Next.js plugin is used to integrate Intlayer with Next.js. It ensures the building of content declaration files and monitors them in development mode. It defines Intlayer environment variables within the Webpack or Turbopack environments. Additionally, it provides aliases to optimize performance and ensures compatibility with server components.

Step 4: Configure Middleware for Locale Detection

Set up middleware to automatically detect and handle the user's preferred locale:

export { intlayerMiddleware as middleware } from "next-intlayer/middleware";export const config = {  matcher:    "/((?!api|static|assets|robots|sitemap|sw|service-worker|manifest|.*\\..*|_next).*)",};

Adapt the matcher parameter to match the routes of your application. For more details, refer to the Next.js documentation on configuring the matcher.

Step 5: Define Dynamic Locale Routes

Implement dynamic routing to serve localized content based on the user's locale.

1. Create Locale-Specific Pages:

   Rename your main page file to include the [locale] dynamic segment.

   bash

   mv src/pages/index.tsx src/pages/[locale]/index.tsx

2. Update _app.tsx to Handle Localization:

   Modify your _app.tsx to include Intlayer providers.

   src/pages/_app.tsx

   import type { FC } from "react";import type { AppProps } from "next/app";import { IntlayerClientProvider } from "next-intlayer";const App = FC<AppProps>({ Component, pageProps }) => {  const { locale } = pageProps;  return (    <IntlayerClientProvider locale={locale}>      <Component {...pageProps} />    </IntlayerClientProvider>  );}export default MyApp;

3. Set Up getStaticPaths and getStaticProps:

   In your [locale]/index.tsx, define the paths and props to handle different locales.

   src/pages/[locale]/index.tsx

   import type { FC } from "react";import type { GetStaticPaths, GetStaticProps } from "next";import { type Locales, getConfiguration } from "intlayer";const HomePage: FC = () => <div>{/* Your content here */}</div>;export const getStaticPaths: GetStaticPaths = () => {  const { internationalization } = getConfiguration();  const { locales } = internationalization;  const paths = locales.map((locale) => ({    params: { locale },  }));  return { paths, fallback: false };};export const getStaticProps: GetStaticProps = ({ params }) => {  const locale = params?.locale as string;  return {    props: {      locale,    },  };};export default HomePage;

getStaticPaths and getStaticProps ensure that your application pre-builds the necessary pages for all locales in Next.js Page Router. This approach reduces runtime computation and leads to an improved user experience. For more details, refer to the Next.js documentation on getStaticPaths and getStaticProps.

Step 6: Declare Your Content

Create and manage your content declarations to store translations.

import { t, type DeclarationContent } from "intlayer";const homeContent = {  key: "home",  content: {    title: t({      en: "Welcome to My Website",      fr: "Bienvenue sur mon site Web",      es: "Bienvenido a mi sitio web",    }),    description: t({      en: "Get started by editing this page.",      fr: "Commencez par éditer cette page.",      es: "Comience por editar esta página.",    }),  },} satisfies DeclarationContent;export default homeContent;

For more information on declaring content, refer to the content declaration guide.

Step 7: Utilize Content in Your Code

Access your content dictionaries throughout your application to display translated content.

import type { FC } from "react";import { useIntlayer } from "next-intlayer";import { ComponentExample } from "@components/ComponentExample";const HomePage: FC = () => {  const content = useIntlayer("home");  return (    <div>      <h1>{content.title}</h1>      <p>{content.description}</p>      <ComponentExample />      {/* Additional components */}    </div>  );};// ... Rest of the code, including getStaticPaths and getStaticPropsexport default HomePage;

import type { FC } from "react";import { useIntlayer } from "next-intlayer";export const ComponentExample: FC = () => {  const content = useIntlayer("component-example"); // Ensure you have a corresponding content declaration  return (    <div>      <h2>{content.title}</h2>      <p>{content.content}</p>    </div>  );};

When using translations in string attributes (e.g., alt, title, href, aria-label), call the value of the function as follows:

jsx

<img src={content.image.src.value} alt={content.image.value} />

To Learn more about the useIntlayer hook, refer to the documentation.

(Optional) Step 8: Internationalize Your Metadata

To internationalize metadata such as page titles and descriptions, use the getStaticProps function in conjunction with Intlayer's getTranslationContent function.

import { GetStaticPaths, GetStaticProps } from "next";import { type IConfigLocales, getTranslationContent, Locales } from "intlayer";import { useIntlayer } from "next-intlayer";interface HomePageProps {  locale: string;  metadata: Metadata;}const HomePage = ({ metadata }: HomePageProps) => {  // Metadata can be used in the head or other components as needed  return (    <div>      <Head>        <title>{metadata.title}</title>        <meta name="description" content={metadata.description} />      </Head>      {/* Additional content */}    </div>  );};export const getStaticProps: GetStaticProps = async ({ params }) => {  const locale = params?.locale as string;  const t = <T,>(content: IConfigLocales<T>) =>    getTranslationContent(content, locale);  const metadata = {    title: t({      en: "My Website",      fr: "Mon Site Web",      es: "Mi Sitio Web",    }),    description: t({      en: "Welcome to my website.",      fr: "Bienvenue sur mon site Web.",      es: "Bienvenido a mi sitio web.",    }),  };  return {    props: {      locale,      metadata,    },  };};export default HomePage;// ... Rest of the code including getStaticPaths

(Optional) Step 9: Change the Language of Your Content

To allow users to switch languages dynamically, use the setLocale function provided by the useLocale hook.

import {  Locales,  getHTMLTextDir,  getLocaleName,  getLocalizedUrl,} from "intlayer";import { useLocalePageRouter } from "next-intlayer";import { type FC } from "react";import Link from "next/link";const LocaleSwitcher: FC = () => {  const { locale, pathWithoutLocale, availableLocales, setLocale } =    useLocalePageRouter();  return (    <div>      <button popoverTarget="localePopover">{getLocaleName(locale)}</button>      <div id="localePopover" popover="auto">        {availableLocales.map((localeItem) => (          <Link            href={getLocalizedUrl(pathWithoutLocale, localeItem)}            hrefLang={localeItem}            key={localeItem}            aria-current={locale === localeItem ? "page" : undefined}            onClick={(e) => {              e.preventDefault();              setLocale(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>        ))}      </div>    </div>  );};

The useLocalePageRouter API is the same as useLocale. To Learn more about the useLocale hook, refer to the documentation.

Documentation references:

• getLocaleName hook
• getLocalizedUrl hook
• getHTMLTextDir hook
• hrefLang attribute
• lang attribute
• dir attribute
• aria-current attribute

(Optional) Step 10: Creating a Localized Link Component

To ensure that your application’s navigation respects the current locale, you can create a custom Link component. This component automatically prefixes internal URLs with the current language, so that. For example, when a French-speaking user clicks on a link to the "About" page, they are redirected to /fr/about instead of /about.

This behavior is useful for several reasons:

• SEO and User Experience: Localized URLs help search engines index language-specific pages correctly and provide users with content in their preferred language.
• Consistency: By using a localized link throughout your application, you guarantee that navigation stays within the current locale, preventing unexpected language switches.
• Maintainability: Centralizing the localization logic in a single component simplifies the management of URLs, making your codebase easier to maintain and extend as your application grows.

Below is the implementation of a localized Link component in TypeScript:

"use client";import { getLocalizedUrl } from "intlayer";import NextLink, { type LinkProps as NextLinkProps } from "next/link";import { useLocale } from "next-intlayer";import { forwardRef, PropsWithChildren, type ForwardedRef } from "react";/** * Utility function to check whether a given URL is external. * If the URL starts with http:// or https://, it's considered external. */export const checkIsExternalLink = (href?: string): boolean =>  /^https?:\/\//.test(href ?? "");/** * A custom Link component that adapts the href attribute based on the current locale. * For internal links, it uses `getLocalizedUrl` to prefix the URL with the locale (e.g., /fr/about). * This ensures that navigation stays within the same locale context. */export const Link = forwardRef<  HTMLAnchorElement,  PropsWithChildren<NextLinkProps>>(({ href, children, ...props }, ref: ForwardedRef<HTMLAnchorElement>) => {  const { locale } = useLocale();  const isExternalLink = checkIsExternalLink(href.toString());  // If the link is internal and a valid href is provided, get the localized URL.  const hrefI18n: NextLinkProps["href"] =    href && !isExternalLink ? getLocalizedUrl(href.toString(), locale) : href;  return (    <NextLink href={hrefI18n} ref={ref} {...props}>      {children}    </NextLink>  );});Link.displayName = "Link";

How It Works

• Detecting External Links:
  The helper function checkIsExternalLink determines whether a URL is external. External links are left unchanged because they do not need localization.

• Retrieving the Current Locale:
  The useLocale hook provides the current locale (e.g., fr for French).

• Localizing the URL:
  For internal links (i.e., non-external), getLocalizedUrl is used to automatically prefix the URL with the current locale. This means that if your user is in French, passing /about as the href will transform it to /fr/about.

• Returning the Link:
  The component returns an <a> element with the localized URL, ensuring that navigation is consistent with the locale.

By integrating this Link component across your application, you maintain a coherent and language-aware user experience while also benefitting from improved SEO and usability.

Configure TypeScript

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

Ensure your TypeScript configuration includes the autogenerated types.

{  // ... Your existing TypeScript configurations  "include": [    // ... Your existing TypeScript configurations    ".intlayer/**/*.ts", // Include the auto-generated types  ],}

Git Configuration

To keep your repository clean and avoid committing generated files, it's recommended to ignore files created by Intlayer.

Add the following lines to your .gitignore file:

# Ignore the files generated by Intlayer.intlayer

Additional Resources

• Intlayer Documentation: GitHub Repository
• Content Declaration Guide: Content Declaration
• Configuration Documentation: Configuration Guide

By following this guide, you can effectively integrate Intlayer into your Next.js application using the Page Router, enabling robust and scalable internationalization support for your web projects.

Go Further

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