Translate your Next.js 16 website using Intlayer | Internationalisation (i18n)

See Application Template on GitHub.

Table of Contents

What is Intlayer?

Intlayer is an innovative, open-source internationalisation (i18n) library designed to simplify multilingual support in modern web applications. Intlayer seamlessly integrates with the latest Next.js 16 framework, including its powerful App Router. It is optimised to work with Server Components for efficient rendering and is fully compatible with Turbopack.

With Intlayer, you can:

• Easily manage translations using declarative dictionaries at the component level.
• Dynamically localise metadata, routes, and content.
• Access translations in both client-side and server-side components.
• 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 16. If you are using Next.js Page Router, you can refer to this guide. Locale routing is useful for SEO, bundle size, and performance. If you don't need it, you can refer to this guide. For Next.js 12, 13, 14 with App Router, refer to this guide.

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

Step 1: Install Dependencies

Install the necessary packages using npm:

npm install intlayer next-intlayernpx intlayer init

• intlayer

  The core package that provides internationalisation 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 internationalisation. Additionally, it includes the Next.js plugin for integrating Intlayer with Webpack or Turbopack, as well as proxy for detecting the user's preferred locale, managing cookies, and handling URL redirection.

Step 2: Configure Your Project

Here is the final structure that we will make:

.├── src│   ├── app│   │   ├── [locale]│   │   │   ├── layout.tsx            # Locale layout for the Intlayer provider│   │   │   ├── page.content.ts│   │   │   └── page.tsx│   │   └── layout.tsx                # Root layout for style and global providers│   ├── components│   │   ├── client-component-example.content.ts│   │   ├── ClientComponentExample.tsx│   │   ├── LocaleSwitcher│   │   │   ├── localeSwitcher.content.ts│   │   │   └── LocaleSwitcher.tsx│   │   ├── server-component-example.content.ts│   │   └── ServerComponentExample.tsx│   └── proxy.ts├── intlayer.config.ts├── next.config.ts├── package.json└── tsconfig.json

If you don't want locale routing, intlayer can be used as a simple provider / hook. See this guide for more details.

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

import { Locales, type IntlayerConfig } from "intlayer";

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

export default config;

Through this configuration file, you can set up localised URLs, proxy 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 Next.js Configuration

Configure your Next.js setup to use Intlayer:

import type { NextConfig } from "next";
import { withIntlayer } from "next-intlayer/server";

const nextConfig: NextConfig = {
  /* config options here */
};

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 optimise performance and ensures compatibility with server components.

The withIntlayer() function is a promise function. It allows to prepare the intlayer dictionaries before the build starts. If you want to use it with other plugins, you can await it. Example:

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const nextConfig = await withIntlayer(nextConfig);const nextConfigWithOtherPlugins = withOtherPlugins(nextConfig);export default nextConfigWithOtherPlugins;

If you want to use it synchronously, you can use the withIntlayerSync() function. Example:

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const nextConfig = withIntlayerSync(nextConfig);const nextConfigWithOtherPlugins = withOtherPlugins(nextConfig);export default nextConfigWithOtherPlugins;

Intlayer automatically detects whether your project is using webpack or Turbopack based on the command-line flags --webpack, --turbo, or --turbopack, as well as your current Next.js version.

Since next>=16, if you are using Rspack, you must explicitly force Intlayer to use the webpack configuration by disabling Turbopack:

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withRspack(withIntlayer(nextConfig, { enableTurbopack: false }));

Step 4: Define Dynamic Locale Routes

Remove everything from RootLayout and replace it with the following code:

import type { PropsWithChildren, FC } from "react";
import "./globals.css";

const RootLayout: FC<PropsWithChildren> = ({ children }) => (
  // You can still wrap the children with other providers, Like `next-themes`, `react-query`, `framer-motion`, etc.
  <>{children}</>
);

export default RootLayout;

Keeping the RootLayout component empty allows to set the lang and dir attributes to the <html> tag.

To implement dynamic routing, provide the path for the locale by adding a new layout in your [locale] directory:

import { type NextLayoutIntlayer, IntlayerClientProvider } from "next-intlayer";
import { Inter } from "next/font/google";
import { getHTMLTextDir } from "intlayer";

const inter = Inter({ subsets: ["latin"] });

const LocaleLayout: NextLayoutIntlayer = async ({ children, params }) => {
  const { locale } = await params;
  return (
    <html lang={locale} dir={getHTMLTextDir(locale)}>
      <body className={inter.className}>
        <IntlayerClientProvider locale={locale}>
          {children}
        </IntlayerClientProvider>
      </body>
    </html>
  );
};

export default LocaleLayout;

The [locale] path segment is used to define the locale. Example: /en-GB/about will refer to en-GB and /fr/about to fr.

At this stage, you will encounter the error: Error: Missing <html> and <body> tags in the root layout.. This is expected because the /app/page.tsx file is no longer in use and can be removed. Instead, the [locale] path segment will activate the /app/[locale]/page.tsx page. Consequently, pages will be accessible via paths like /en, /fr, /es in your browser. To set the default locale as the root page, refer to the proxy setup in step 7.

Then, implement the generateStaticParams function in your application Layout.

export { generateStaticParams } from "next-intlayer"; // Line to insert

const LocaleLayout: NextLayoutIntlayer = async ({ children, params }) => {
  /*... Rest of the code*/
};

export default LocaleLayout;

generateStaticParams ensures that your application pre-builds the necessary pages for all locales, reducing runtime computation and improving the user experience. For more details, refer to the Next.js documentation on generateStaticParams.

Intlayer works with export const dynamic = 'force-static'; to ensure that the pages are pre-built for all locales.

Step 5: Declare Your Content

Create and manage your content declarations to store translations:

import { t, type Dictionary } from "intlayer";

const pageContent = {
  key: "page",
  content: {
    getStarted: {
      main: t({
        en: "Get started by editing",
        fr: "Commencez par éditer",
        es: "Comience por editar",
      }),
      pageLink: "src/app/page.tsx",
    },
  },
} satisfies Dictionary;

export default pageContent;

Your content declarations can be defined anywhere in your application as soon they are included into the contentDir directory (by default, ./src). And match the content declaration file extension (by default, .content.{json,ts,tsx,js,jsx,mjs,cjs}).

For more details, refer to the content declaration documentation.

Step 6: Utilise Content in Your Code

Access your content dictionaries throughout your application:

import type { FC } from "react";
import { ClientComponentExample } from "@components/ClientComponentExample";
import { ServerComponentExample } from "@components/ServerComponentExample";
import { type NextPageIntlayer } from "next-intlayer";
import { IntlayerServerProvider, useIntlayer } from "next-intlayer/server";

const PageContent: FC = () => {
  const content = useIntlayer("page");

  return (
    <>
      <p>{content.getStarted.main}</p>
      <code>{content.getStarted.pageLink}</code>
    </>
  );
};

const Page: NextPageIntlayer = async ({ params }) => {
  const { locale } = await params;

  return (
    <IntlayerServerProvider locale={locale}>
      <PageContent />
      <ServerComponentExample />

      <ClientComponentExample />
    </IntlayerServerProvider>
  );
};

export default Page;

• IntlayerClientProvider is used to provide the locale to client-side components. It can be placed in any parent component, including the layout. However, placing it in a layout is recommended because Next.js shares layout code across pages, making it more efficient. By using IntlayerClientProvider in the layout, you avoid reinitialising it for every page, improving performance and maintaining a consistent localisation context throughout your application.

• IntlayerServerProvider is used to provide the locale to the server children. It cannot be set set in the layout.

  Layout and page cannot share a common server context because the server context system is based on a per-request data store (via React's cache mechanism), causing each "context" to be re-created for different segments of the application. Placing the provider in a shared layout would break this isolation, preventing the correct propagation of the server context values to your server components.

"use client";

import type { FC } from "react";
import { useIntlayer } from "next-intlayer";

export const ClientComponentExample: FC = () => {
  const content = useIntlayer("client-component-example"); // Create related content declaration

  return (
    <div>
      <h2>{content.title}</h2>
      <p>{content.content}</p>
    </div>
  );
};

import type { FC } from "react";
import { useIntlayer } from "next-intlayer/server";

export const ServerComponentExample: FC = () => {
  const content = useIntlayer("server-component-example"); // Create related content declaration

  return (
    <div>
      <h2>{content.title}</h2>
      <p>{content.content}</p>
    </div>
  );
};

If you want to use your content in a string attribute, such as alt, title, href, aria-label, etc., you can use the value of the function, like:

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<img src="{content.image.src.value}" alt="{content.image.value}" /><img src="{content.image.src.toString()}" alt="{content.image.toString()}" /><img src="{String(content.image.src)}" alt="{String(content.image)}" />

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

(Optional) Step 7: Configure Proxy for Locale Detection

Set up proxy to detect the user's preferred locale:

export { intlayerProxy as proxy } from "next-intlayer/proxy";

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

The intlayerProxy is used to detect the user's preferred locale and redirect them to the appropriate URL as specified in the configuration. Additionally, it enables saving the user's preferred locale in a cookie.

If you need to chain several proxies together (for example, intlayerProxy with authentication or custom proxies), Intlayer now provides a helper called multipleProxies.

import { multipleProxies, intlayerProxy } from "next-intlayer/proxy";import { customProxy } from "@utils/customProxy";export const proxy = multipleProxies([intlayerProxy, customProxy]);

(Optional) Step 8: Internationalisation of your metadata

In the case you want to internationalise your metadata, such as the title of your page, you can use the generateMetadata function provided by Next.js. Inside, you can retrieve the content from the getIntlayer function to translate your metadata.

import { type Dictionary, t } from "intlayer";
import { Metadata } from "next";

const metadataContent = {
  key: "page-metadata",
  content: {
    title: t({
      en: "Create Next App",
      fr: "Créer une application Next.js",
      es: "Crear una aplicación Next.js",
    }),
    description: t({
      en: "Generated by create next app",
      fr: "Généré par create next app",
      es: "Generado por create next app",
    }),
  },
} satisfies Dictionary<Metadata>;

export default metadataContent;

import { getIntlayer, getMultilingualUrls } from "intlayer";
import type { Metadata } from "next";
import type { LocalPromiseParams } from "next-intlayer";

export const generateMetadata = async ({
  params,
}: LocalPromiseParams): Promise<Metadata> => {
  const { locale } = await params;

  const metadata = getIntlayer("page-metadata", locale);

  /**
   * Generates an object containing all url for each locale.
   *
   * Example:
   * ```ts
   *  getMultilingualUrls('/about');
   *
   *  // Returns
   *  // {
   *  //   en: '/about',
   *  //   fr: '/fr/about',
   *  //   es: '/es/about',
   *  // }
   * ```
   */
  const multilingualUrls = getMultilingualUrls("/");
  const localizedUrl =
    multilingualUrls[locale as keyof typeof multilingualUrls];

  return {
    ...metadata,
    alternates: {
      canonical: localizedUrl,
      languages: { ...multilingualUrls, "x-default": "/" },
    },
    openGraph: {
      url: localizedUrl,
    },
  };
};

// ... Rest of the code

Note that the getIntlayer function imported from next-intlayer returns your content wrapped in an IntlayerNode, allowing integration with the visual editor. In contrast, the getIntlayer function imported from intlayer returns your content directly without additional properties.

Alternatively, you can use the getTranslation function to declare your metadata. However, using content declaration files is recommended to automate the translation of your metadata and externalize the content at some point.

import {
  type IConfigLocales,
  getTranslation,
  getMultilingualUrls,
} from "intlayer";
import type { Metadata } from "next";
import type { LocalPromiseParams } from "next-intlayer";

export const generateMetadata = async ({
  params,
}: LocalPromiseParams): Promise<Metadata> => {
  const { locale } = await params;
  const t = <T>(content: IConfigLocales<T>) => getTranslation(content, locale);

  return {
    title: t<string>({
      en: "My title",
      fr: "Mon titre",
      es: "Mi título",
    }),
    description: t({
      en: "My description",
      fr: "Ma description",
      es: "Mi descripción",
    }),
  };
};

// ... Rest of the code

Learn more about the metadata optimisation on the official Next.js documentation.

(Optional) Step 9: Internationalisation of your sitemap.xml and robots.txt

To internationalise your sitemap.xml and robots.txt, you can use the getMultilingualUrls function provided by Intlayer. This function allows you to generate multilingual URLs for your sitemap.

import { getMultilingualUrls } from "intlayer";
import type { MetadataRoute } from "next";

const sitemap = (): MetadataRoute.Sitemap => [
  {
    url: "https://example.com",
    alternates: {
      languages: {
        ...getMultilingualUrls("https://example.com"),
        "x-default": "https://example.com",
      },
    },
  },
  {
    url: "https://example.com/login",
    alternates: {
      languages: {
        ...getMultilingualUrls("https://example.com/login"),
        "x-default": "https://example.com/login",
      },
    },
  },
  {
    url: "https://example.com/register",
    alternates: {
      languages: {
        ...getMultilingualUrls("https://example.com/register"),
        "x-default": "https://example.com/register",
      },
    },
  },
];

export default sitemap;

import type { MetadataRoute } from "next";
import { getMultilingualUrls } from "intlayer";

const getAllMultilingualUrls = (urls: string[]) =>
  urls.flatMap((url) => Object.values(getMultilingualUrls(url)) as string[]);

const robots = (): MetadataRoute.Robots => ({
  rules: {
    userAgent: "*",
    allow: ["/"],
    disallow: getAllMultilingualUrls(["/login", "/register"]),
  },
  host: "https://example.com",
  sitemap: `https://example.com/sitemap.xml`,
});

export default robots;

Learn more about the sitemap optimisation on the official Next.js documentation. Learn more about the robots.txt optimisation on the official Next.js documentation.

(Optional) Step 10: Change the language of your content

To change the language of your content in Next.js, the recommended way is to use the Link component to redirect users to the appropriate localised page. The Link component enables prefetching of the page, which helps avoid a full page reload.

"use client";

import type { FC } from "react";
import {
  Locales,
  getHTMLTextDir,
  getLocaleName,
  getLocalizedUrl,
} from "intlayer";
import { useLocale } from "next-intlayer";
import Link from "next/link";

export const LocaleSwitcher: FC = () => {
  const { locale, pathWithoutLocale, availableLocales, setLocale } =
    useLocale();

  return (
    <div>
      <button popoverTarget="localePopover">{getLocaleName(locale)}</button>
      <div id="localePopover" popover="auto">
        {availableLocales.map((localeItem) => (
          <Link
            href={getLocalizedUrl(pathWithoutLocale, localeItem)}
            key={localeItem}
            aria-current={locale === localeItem ? "page" : undefined}
            onClick={() => setLocale(localeItem)}
            replace // Will ensure that the "go back" browser button will redirect to the previous page
          >
            <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>
  );
};

An alternative way is to use the setLocale function provided by the useLocale hook. This function will not allow prefetching the page. See the useLocale hook documentation for more details.

You can also set a function in the onLocaleChange option to trigger a custom function when the locale changes.

"use client";import { useRouter } from "next/navigation";import { useLocale } from "next-intlayer";import { getLocalizedUrl } from "intlayer";// ... Rest of the codeconst router = useRouter();const { setLocale } = useLocale({  onLocaleChange: (locale) => {    router.push(getLocalizedUrl(pathWithoutLocale, locale));  },});return (  <button onClick={() => setLocale(Locales.FRENCH)}>Change to French</button>);

Documentation references:

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

(Optional) Step 11: Creating a Localised 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. 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 behaviour is useful for several reasons:

• SEO and User Experience: Localised URLs help search engines index language-specific pages correctly and provide users with content in their preferred language.
• Consistency: By using a localised link throughout your application, you guarantee that navigation stays within the current locale, preventing unexpected language switches.
• Maintainability: Centralising the localisation 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 localised 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 type { PropsWithChildren, FC } 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: FC<PropsWithChildren<NextLinkProps>> = ({
  href,
  children,
  ...props
}) => {
  const { locale } = useLocale();
  const isExternalLink = checkIsExternalLink(href.toString());

  // If the link is internal and a valid href is provided, get the localised URL.
  const hrefI18n: NextLinkProps["href"] =
    href && !isExternalLink ? getLocalizedUrl(href.toString(), locale) : href;

  return (
    <NextLink href={hrefI18n} {...props}>
      {children}
    </NextLink>
  );
};

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 localisation.

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

• Localising 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 localised 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.

(Optional) Step 12: Get the current locale in Server Actions

If you need the active locale inside a Server Action (e.g., to localise emails or run locale-aware logic), call getLocale from next-intlayer/server:

"use server";import { getLocale } from "next-intlayer/server";export const myServerAction = async () => {  const locale = await getLocale();  // Do something with the locale};

The getLocale function follows a cascading strategy to determine the user's locale:

1. First, it checks the request headers for a locale value that may have been set by the proxy
2. If no locale is found in headers, it looks for a locale stored in cookies
3. If no cookie is found, it attempts to detect the user's preferred language from their browser settings
4. As a last resort, it falls back to the application's configured default locale

This ensures the most appropriate locale is selected based on available context.

(Optional) Step 13: Optimise your bundle size

When using next-intlayer, dictionaries are included in the bundle for every page by default. To optimise bundle size, Intlayer provides an optional SWC plugin that intelligently replace useIntlayer calls using macros. This ensures dictionaries are only included in bundles for pages that actually use them.

To enable this optimisation, install the @intlayer/swc package. Once installed, next-intlayer will automatically detect and use the plugin:

npm install @intlayer/swc --save-dev

Note: This optimisation is only available for Next.js 13 and above.

Note: This package is not installed by default because SWC plugins are still experimental on Next.js. It may change in the future.

Note: If you set the option as importMode: 'dynamic' or importMode: 'fetch' (in the dictionary configuration), it will rely on Suspense, so you will have to wrap your useIntlayer calls in a Suspense boundary. That means, you will not be able to use the useIntlayer directly at the top level of your Page / Layout component.

Watch dictionaries changes on Turbopack

When using Turbopack as your development server with the next dev command, dictionary changes will not be automatically detected by default.

This limitation occurs because Turbopack cannot run webpack plugins in parallel to monitor changes in your content files. To work around this, you'll need to use the intlayer watch command to run both the development server and the Intlayer build watcher simultaneously.

{  // ... Your existing package.json configurations  "scripts": {    // ... Your existing scripts configurations    "dev": "intlayer watch --with 'next dev'",  },}

If you are using next-intlayer@<=6.x.x, you need to keep the --turbopack flag to make the Next.js 16 application work correctly with Turbopack. We recommend using next-intlayer@>=7.x.x to avoid this limitation.

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

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 externalise your content using the CMS.