Internationalisation (i18n) is the process of designing an application to be easily adaptable to different languages and regions without engineering changes. In this article, you will learn how to set up i18n in a Next.js application and create a language switcher to toggle between English and Spanish using next-intl.
First, you need to install the next-intl library, which facilitates managing internationalisation in Next.js. Run the following command in your terminal:
npm install next-intl
The project structure will be as follows:
├── messages │ ├── en.json │ └── es.json ├── next.config.mjs └── src ├── i18n.ts ├── middleware.ts └── app └── [locale] ├── layout.tsx └── page.tsx
Create a messages directory at the root of your project. Inside this directory, add JSON files for each language you want to support.
{ "greeting": "Hello Codú", "farewell": "Goodbye Codú" }
{ "greeting": "Hola Codú", "farewell": "Adiós Codú" }
These files contain the translations of the phrases that your application will use.
Configure Next.js to support internationalisation in next.config.mjs.
import { getRequestConfig } from 'next-intl/server'; // List of supported languages const locales = ['en', 'es']; export default getRequestConfig(async ({ locale }) => { // Validate that the incoming `locale` parameter is valid if (!locales.includes(locale)) { return { notFound: true }; } return { messages: (await import(`./messages/${locale}.json`)).default }; });
This file configures Next.js to load the correct translation messages based on the requested language.
Create middleware to handle redirection and setting the default language.
import createMiddleware from 'next-intl/middleware'; export default createMiddleware({ // List of all supported languages locales: ['en', 'es'], // Default language defaultLocale: 'en' }); export const config = { // Only match internationalised pathnames matcher: ['/', '/(en|es)/:path*'] };
This middleware handles redirecting to the default language if none is specified.
Create a configuration file to manage internationalisation settings.
import { notFound } from 'next/navigation'; import { getRequestConfig } from 'next-intl/server'; const locales = ['en', 'es']; export default getRequestConfig(async ({ locale }) => { if (!locales.includes(locale as any)) notFound(); return { messages: (await import(`../messages/${locale}.json`)).default }; });
This file validates the locales and loads the corresponding messages.
Configure the layout and main page to support internationalisation.
import { useLocale } from 'next-intl'; import { ReactNode } from 'react'; export default function Layout({ children }: { children: ReactNode }) { const locale = useLocale(); return ( <html lang={locale}> <body>{children}</body> </html> ); }
import { useTranslations } from 'next-intl'; export default function Page() { const t = useTranslations(); return ( <div> <h1>{t('greeting')}</h1> <p>{t('farewell')}</p> </div> ); }
These files configure the layout and main page to use the translations.
Finally, create a language switcher to toggle between English and Spanish.
'use client'; import { useLocale } from 'next-intl'; import { useRouter } from 'next/navigation'; import { ChangeEvent, useTransition } from 'react'; export default function LocalSwitcher() { const [isPending, startTransition] = useTransition(); const router = useRouter(); const localActive = useLocale(); const onSelectChange = (e: ChangeEvent<HTMLSelectElement>) => { const nextLocale = e.target.value; startTransition(() => { router.replace(`/${nextLocale}`); }); }; return ( <label className='border-2 rounded'> <p className='sr-only'>Change language</p> <select defaultValue={localActive} className='bg-transparent py-2' onChange={onSelectChange} disabled={isPending} > <option value='en'>English</option> <option value='es'>Spanish</option> </select> </label> ); }
This component allows users to change the interface language.
With these steps, you have successfully set up internationalisation in your Next.js application and created a language switcher to toggle between English and Spanish. This will allow your application to support multiple languages and provide a localised user experience.
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