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How do you internationalize (i18n) a Next.js App Router app?

Q: How do you internationalize (i18n) a Next.js App Router app?

**TL;DR.** The App Router has **no built-in i18n routing** (unlike Pages), so you use a [lang] dynamic segment plus **middleware** to detect/redirect by locale, and a library (**next-intl**, next-i18next) to load translations. generateStaticParams pre-renders each locale; **metadata** is localized per route. middleware detect locale /[lang]/… /en, /fr <path class='

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Locale routing and translation in the App Router.

nextjsi18ninternationalizationrouting

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Read the code

Locale segment + static params

// app/[lang]/layout.tsx
export function generateStaticParams() {
  return [{ lang: 'en' }, { lang: 'fr' }, { lang: 'de' }];   // prerender each locale
}
export default async function Layout({ children, params }) {
  const { lang } = await params;
  return <html lang={lang}>{children}</html>;
}
// middleware redirects '/' → '/en' based on Accept-Language.

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