# How to add i18n routing

# Routing Synced With I18n

Open the next.config.js file and add the i18 property with the languages you need

i18n: {
  locales: ['en', 'fr', 'ar'],
  defaultLocale: 'en'
},

Create a useEffect in the src/pages/_app.tsx file to watch changes of i18n language and to preserve the language in case the page is reloaded:

import { useEffect } from 'react'
import { useRouter } from 'next/router'
import { useTranslation } from 'react-i18next'

const App = () => {
  const router = useRouter()
  const { i18n } = useTranslation()
  const { locale } = router

  useEffect(() => {
    if (locale !== 'en') {
      i18n.changeLanguage(locale)
    }
  }, [locale])

  return (
    ...
  )
}

export default App

To switch a language, push the locale parameter with router.push:

Import locale from the useRouter hook and add the locale prop to every NextJS link that is used in your app:

import Link from 'next/link'
import { useRouter } from 'next/router'

const Component = () => {
  const router = useRouter()
  const { locale } = router

  return <Link href='...' locale={locale}>text</Link>
}

export default Component

If you have getStaticPaths & getStaticProps in your component then you'll have to do the following otherwise you'll be redirected to 404

export const getStaticProps = ({ locale, locales }) => {
  return {
    props: {
      locale,
      locales,
    },
  }
}

export const getStaticPaths = ({ locales }) => {
  const paths = []

  for (const locale of locales) {
    paths.push({ params: { ... }, locale })
    paths.push({ params: { ... }, locale })
  }

  return {
    paths,
    fallback: true,
  }
}