App Router setup with i18n routing

In order to use unique pathnames for every language that your app supports, next-intl can be used to handle the following routing setups:

Prefix-based routing (e.g. /en/about)
Domain-based routing (e.g. en.example.com/about)

In either case, next-intl integrates with the App Router by using a top-level [locale] dynamic segment (opens in a new tab) that can be used to provide content in different languages.

Getting started

If you haven't done so already, create a Next.js app (opens in a new tab) that uses the App Router and run:

npm install next-intl

Now, we're going to create the following file structure:

├── messages
│   ├── en.json (1)
│   └── ...
├── next.config.mjs (2)
└── src
    ├── i18n
    │   ├── routing.ts (3)
    │   └── request.ts (5)
    ├── middleware.ts (4)
    └── app
        └── [locale]
            ├── layout.tsx (6)
            └── page.tsx (7)

In case you're migrating an existing app to next-intl, you'll typically move your existing pages into the [locale] folder as part of the setup.

Let's set up the files:

`messages/en.json`

Messages represent the translations that are available per language and can be provided either locally or loaded from a remote data source.

The simplest option is to add JSON files in your local project folder:

messages/en.json

{
  "HomePage": {
    "title": "Hello world!",
    "about": "Go to the about page"
  }
}

`next.config.mjs`

Now, set up the plugin which creates an alias to provide a request-specific i18n configuration to Server Components—more on this in the following steps.

next.config.mjs

import createNextIntlPlugin from 'next-intl/plugin';
 
const withNextIntl = createNextIntlPlugin();
 
/** @type {import('next').NextConfig} */
const nextConfig = {};
 
export default withNextIntl(nextConfig);

`src/i18n/routing.ts`

We'll integrate with Next.js' routing in two places:

Middleware: Negotiates the locale and handles redirects & rewrites (e.g. / → /en)
Navigation APIs: Lightweight wrappers around Next.js' navigation APIs like <Link />

This enables you to work with pathnames like /about, while i18n aspects like language prefixes are handled behind the scenes.

To share the configuration between these two places, we'll set up routing.ts:

src/i18n/routing.ts

import {defineRouting} from 'next-intl/routing';
import {createSharedPathnamesNavigation} from 'next-intl/navigation';
 
export const routing = defineRouting({
  // A list of all locales that are supported
  locales: ['en', 'de'],
 
  // Used when no locale matches
  defaultLocale: 'en'
});
 
// Lightweight wrappers around Next.js' navigation APIs
// that will consider the routing configuration
export const {Link, redirect, usePathname, useRouter} =
  createSharedPathnamesNavigation(routing);

Depending on your requirements, you may wish to customize your routing configuration later—but let's finish with the setup first.

`src/middleware.ts`

Once we have our routing configuration in place, we can use it to set up the middleware.

src/middleware.ts

import createMiddleware from 'next-intl/middleware';
import {routing} from './i18n/routing';
 
export default createMiddleware(routing);
 
export const config = {
  // Match only internationalized pathnames
  matcher: ['/', '/(de|en)/:path*']
};

`src/i18n/request.ts`

next-intl creates a request-scoped configuration object, which you can use to provide messages and other options based on the user's locale to Server Components.

src/i18n/request.ts

import {notFound} from 'next/navigation';
import {getRequestConfig} from 'next-intl/server';
import {routing} from './routing';
 
export default getRequestConfig(async ({locale}) => {
  // Validate that the incoming `locale` parameter is valid
  if (!routing.locales.includes(locale as any)) notFound();
 
  return {
    messages: (await import(`../../messages/${locale}.json`)).default
  };
});

Can I move this file somewhere else?

This file is supported out-of-the-box as ./i18n/request.ts both in the src folder as well as in the project root with the extensions .ts, .tsx, .js and .jsx.

If you prefer to move this file somewhere else, you can optionally provide a path to the plugin:

next.config.mjs

const withNextIntl = createNextIntlPlugin(
  // Specify a custom path here
  './somewhere/else/request.ts'
);

`src/app/[locale]/layout.tsx`

The locale that was matched by the middleware is available via the locale param and can be used to configure the document language. Additionally, we can use this place to pass configuration from i18n/request.ts to Client Components via NextIntlClientProvider.

app/[locale]/layout.tsx

import {NextIntlClientProvider} from 'next-intl';
import {getMessages} from 'next-intl/server';
 
export default async function LocaleLayout({
  children,
  params: {locale}
}: {
  children: React.ReactNode;
  params: {locale: string};
}) {
  // Providing all messages to the client
  // side is the easiest way to get started
  const messages = await getMessages();
 
  return (
    <html lang={locale}>
      <body>
        <NextIntlClientProvider messages={messages}>
          {children}
        </NextIntlClientProvider>
      </body>
    </html>
  );
}

Note that NextIntlClientProvider automatically inherits configuration from i18n/request.ts here, but messages need to be passed explicitly.

`src/app/[locale]/page.tsx`

And that's it!

Now you can use translations and other functionality from next-intl in your components:

app/[locale]/page.tsx

import {useTranslations} from 'next-intl';
import {Link} from '@/i18n/routing';
 
export default function HomePage() {
  const t = useTranslations('HomePage');
  return (
    <div>
      <h1>{t('title')}</h1>
      <Link href="/about">{t('about')}</Link>
    </div>
  );
}

In case you ran into an issue, have a look at the App Router example to explore a working app.

💡

Next steps:

Usage guide: Learn how to format messages, dates and times
Routing: Set up localized pathnames, domain-based routing & more
Workflows: Integrate deeply with TypeScript and other tools

Static rendering

When using the setup with i18n routing, next-intlwill currently opt into dynamic rendering when APIs like useTranslations are used in Server Components. This is a limitation that we aim to remove in the future, but as a stopgap solution, next-intl provides a temporary API that can be used to enable static rendering:

Add `generateStaticParams` to `app/[locale]/layout.tsx`

Since we are using a dynamic route segment for the [locale] param, we need to pass all possible values to Next.js via generateStaticParams (opens in a new tab) so that the routes can be rendered at build time.

app/[locale]/layout.tsx

import {routing} from '@/i18n/routing';
 
export function generateStaticParams() {
  return routing.locales.map((locale) => ({locale}));
}

Add `unstable_setRequestLocale` to all layouts and pages

next-intl provides a temporary API that can be used to distribute the locale that is received via params in layouts and pages for usage in all Server Components that are rendered as part of the request.

app/[locale]/layout.tsx

import {unstable_setRequestLocale} from 'next-intl/server';
 
export default async function LocaleLayout({children, params: {locale}}) {
  unstable_setRequestLocale(locale);
 
  return (
    // ...
  );
}

app/[locale]/page.tsx

import {unstable_setRequestLocale} from 'next-intl/server';
 
export default function IndexPage({params: {locale}}) {
  unstable_setRequestLocale(locale);
 
  // Once the request locale is set, you
  // can call hooks from `next-intl`
  const t = useTranslations('IndexPage');
 
  return (
    // ...
  );
}

Keep in mind that:

The locale that you pass to unstable_setRequestLocale should be validated (e.g. in i18n/request.ts).
You need to call this function in every page and every layout that you intend to enable static rendering for since Next.js can render layouts and pages independently.

E.g. when you navigate from /settings/profile to /settings/privacy, the /settings segment might not re-render as part of the request. Due to this, it's important that unstable_setRequestLocale is called not only in the parent settings/layout.tsx, but also in the individual pages profile/page.tsx and privacy/page.tsx.

What does "unstable" mean?

unstable_setRequestLocale is meant to be used as a stopgap solution and we aim to remove it in the future in case Next.js adds an API to access parts of the URL (opens in a new tab). If that's the case, you'll get a deprecation notice in a minor version and the API will be removed as part of a major version.

That being said, the API is expected to work reliably if you're cautious to apply it in all relevant places.

How does unstable_setRequestLocale work?

next-intl uses cache() (opens in a new tab) to create a mutable store that holds the current locale. By calling unstable_setRequestLocale, the current locale will be written to the store, making it available to all APIs that require the locale.

Note that the store is scoped to a request and therefore doesn't affect other requests that might be handled in parallel while a given request resolves asynchronously.

Why is this API necessary?

Next.js currently doesn't provide an API to read route params like locale at arbitrary places in Server Components (see vercel/next.js#58862 (opens in a new tab)). The locale is fundamental to all APIs provided by next-intl, therefore passing this as a prop throughout the tree doesn't stand out as particularly ergonomic.

Due to this, next-intl uses its middleware to attach an x-next-intl-locale header to the incoming request, holding the negotiated locale as a value. This technique allows the locale to be read at arbitrary places via headers().get('x-next-intl-locale').

However, the usage of headers opts the route into dynamic rendering.

By using unstable_setRequestLocale, you can provide the locale that is received in layouts and pages via params to next-intl. All APIs from next-intl can now read from this value instead of the header, enabling static rendering.

Use the `locale` param in metadata

In addition to the rendering of your pages, also page metadata needs to qualify for static rendering.

To achieve this, you can forward the locale that you receive from Next.js via params to the awaitable functions from next-intl.

page.tsx

import {getTranslations} from 'next-intl/server';
 
export async function generateMetadata({params: {locale}}) {
  const t = await getTranslations({locale, namespace: 'Metadata'});
 
  return {
    title: t('title')
  };
}

App Router Without i18n routing

App Router setup with i18n routing

Getting started

messages/en.json

next.config.mjs

src/i18n/routing.ts

src/middleware.ts

src/i18n/request.ts

src/app/[locale]/layout.tsx

src/app/[locale]/page.tsx

Static rendering

Add generateStaticParams to app/[locale]/layout.tsx

Add unstable_setRequestLocale to all layouts and pages

Use the locale param in metadata

`messages/en.json`

`next.config.mjs`

`src/i18n/routing.ts`

`src/middleware.ts`

`src/i18n/request.ts`

`src/app/[locale]/layout.tsx`

`src/app/[locale]/page.tsx`

Add `generateStaticParams` to `app/[locale]/layout.tsx`

Add `unstable_setRequestLocale` to all layouts and pages

Use the `locale` param in metadata