Internationalization

Read the Next.js Docs to learn more about implementing I18n in Next.js.

Setup

Define the i18n configurations in a file, we will import it with @/i18n in this guide.

i18n.ts

import type { I18nConfig } from 'fumadocs-core/i18n';
 
export const i18n: I18nConfig = {
  defaultLanguage: 'en',
  languages: ['en', 'cn'],
};

Change your current source configurations.

source.ts

import { i18n } from '@/i18n';
import { loader } from 'fumadocs-core/source';
 
export const source = loader({
  i18n,
  // other options
});

Update the usages to your source:

import { source } from '@/app/source';
 
// get page tree
source.pageTree[params.lang];
 
// get page
source.getPage(params.slug, params.lang);
 
// get pages
source.getPages(params.lang);

Middleware

Create a middleware that redirects users to appropriate locale.

middleware.ts

import { createI18nMiddleware } from 'fumadocs-core/i18n';
import { i18n } from '@/i18n';
 
export default createI18nMiddleware(i18n);
 
export const config = {
  // Matcher ignoring `/_next/` and `/api/`
  matcher: ['/((?!api|_next/static|_next/image|favicon.ico).*)'],
};

Root Layout

Create a dynamic route /app/[lang], and move all special files from /app to the folder.

A I18nProvider is needed for localization. Wrap the root provider inside your I18n provider.

import { RootProvider } from 'fumadocs-ui/provider';
import { I18nProvider } from 'fumadocs-ui/i18n';
 
export default function RootLayout({
  params,
  children,
}: {
  params: { lang: string };
  children: React.ReactNode;
}) {
  return (
    <html lang={params.lang}>
      <body>
        <I18nProvider locale={params.lang}>
          <RootProvider>{children}</RootProvider>
        </I18nProvider>
      </body>
    </html>
  );
}

Docs Page

Make sure to update references to source and configure Static Site Generation correctly.

page.tsx

import { source } from '@/app/source';
import type { Metadata } from 'next';
import {
  DocsPage,
  DocsBody,
  DocsTitle,
  DocsDescription,
} from 'fumadocs-ui/page';
import { notFound } from 'next/navigation';
import defaultMdxComponents from 'fumadocs-ui/mdx';
 
export default async function Page({
  params,
}: {
  params: { lang: string; slug?: string[] };
}) {
  const page = source.getPage(params.slug, params.lang);
  if (!page) notFound();
 
  const MDX = page.data.body;
 
  return (
    <DocsPage toc={page.data.toc}>
      <DocsTitle>{page.data.title}</DocsTitle>
      <DocsDescription>{page.data.description}</DocsDescription>
      <DocsBody>
        <MDX components={{ ...defaultMdxComponents }} />
      </DocsBody>
    </DocsPage>
  );
}
 
export async function generateStaticParams() {
  return source.generateParams();
}
 
export function generateMetadata({
  params,
}: {
  params: { lang: string; slug?: string[] };
}) {
  const page = source.getPage(params.slug, params.lang);
  if (!page) notFound();
 
  return {
    title: page.data.title,
    description: page.data.description,
  } satisfies Metadata;
}

Writing Documents

see Page Conventions to learn how to organize your documents.

Search

Configure i18n on your search solution. For Flexsearch, see Setup I18n.

Adding Translations

We only provide English translation by default, you have to pass your translations to the provider.

import { I18nProvider } from 'fumadocs-ui/i18n';
 
<I18nProvider
  locales={[
    {
      name: 'English',
      locale: 'en',
    },
    {
      name: 'Chinese',
      locale: 'cn',
    },
  ]}
  translations={
    {
      cn: {
        search: 'Translated Content',
      },
    }[locale]
  }
  // other props
/>;

To allow users changing their language, enable i18n on your layouts.

app/layout.config.tsx

import type { HomeLayoutProps } from 'fumadocs-ui/home-layout';
 
export const baseOptions: HomeLayoutProps = {
  i18n: true,
};

Configurations

You can also customise the i18n middleware from i18n.ts.

Hide Locale Prefix

To hide the locale prefix, for example, use / instead of /en, use the hideLocale option.

Mode	Description
`always`	Always hide the prefix, detect locale from cookies
`default-locale`	Only hide the default locale
`never`	Never hide the prefix (default)

It uses NextResponse.rewrite under the hood.

import type { I18nConfig } from 'fumadocs-core/i18n';
 
export const i18n: I18nConfig = {
  defaultLanguage: 'en',
  languages: ['en', 'cn'],
  hideLocale: 'default-locale',
};

It's not recommended to use always. On this mode, locale is stored as a cookie, read and set on the middleware.

This may cause undesired cache problems on your hosting platform, and need to pay extra attention on SEO to ensure search engines can index your pages correctly.