Next-intl library integration in NextJS

Introduction

Next-intl helps you show your website in different languages easily. It makes your app friendly for people who speak different languages.

You want your Next.js website to support English and Spanish.

You need to show dates and numbers in the visitor's local format.

You want to switch languages without reloading the page.

You want to keep all your text translations in one place.

You want to make your app accessible to more users worldwide.

Syntax

NextJS

import {NextIntlProvider} from 'next-intl';

export default function App({Component, pageProps}) {
  return (
    <NextIntlProvider messages={pageProps.messages}>
      <Component {...pageProps} />
    </NextIntlProvider>
  );
}

Wrap your app with NextIntlProvider to provide translations.

Pass the messages prop containing translations for the current language.

Examples

Use useTranslations hook to get translated text inside components.

NextJS

import {useTranslations} from 'next-intl';

export default function Greeting() {
  const t = useTranslations('Greeting');
  return <p>{t('hello')}</p>;
}

Load translation messages based on the current locale in getStaticProps.

NextJS

export async function getStaticProps({locale}) {
  return {
    props: {
      messages: (await import(`../messages/${locale}.json`)).default
    }
  };
}

Sample Program

This example shows a Next.js app using next-intl. The App component wraps everything with NextIntlProvider. The Greeting component uses translations from the Greeting namespace. The getStaticProps function loads the right language messages based on the locale.

NextJS

import {NextIntlProvider, useTranslations} from 'next-intl';

export default function App({Component, pageProps}) {
  return (
    <NextIntlProvider messages={pageProps.messages}>
      <Component {...pageProps} />
    </NextIntlProvider>
  );
}

export function Greeting() {
  const t = useTranslations('Greeting');
  return <h1>{t('hello')}</h1>;
}

export async function getStaticProps({locale}) {
  return {
    props: {
      messages: (await import(`../messages/${locale}.json`)).default
    }
  };
}

Important Notes

Keep your translation files organized by language and namespace for easy management.

Use the useTranslations hook inside components to get translated strings.

Remember to handle fallback languages if a translation is missing.

Summary

Next-intl helps you add multiple languages to your Next.js app.

Wrap your app with NextIntlProvider and load messages per locale.

Use useTranslations hook to get translated text inside components.

Practice

1. What is the main purpose of the NextIntlProvider component in a Next.js app using next-intl?

easy

A. To fetch data from an API

B. To provide translation messages and locale context to the app

C. To handle routing between pages

D. To style components with CSS

Solution

1. Step 1: Understand the role of NextIntlProvider

   The NextIntlProvider wraps the app and supplies translation messages and locale information to all child components.

2. Step 2: Compare with other options

   Fetching data, routing, and styling are unrelated to NextIntlProvider's purpose.

3. Final Answer:

   To provide translation messages and locale context to the app -> Option B

4. Quick Check:

   NextIntlProvider = translation context provider [OK]

Hint: NextIntlProvider always wraps your app to share translations [OK]

Common Mistakes:

• Confusing NextIntlProvider with data fetching
• Thinking it handles routing or styling
• Not realizing it shares locale and messages

2. Which of the following is the correct way to import and use the useTranslations hook in a Next.js component?

easy

A. import { useTranslations } from 'next-intl'; const t = useTranslations('common');

B. import useTranslations from 'next-intl'; const t = useTranslations('common');

C. import { useTranslations } from 'next-intl'; const t = useTranslations();

D. import { useTranslation } from 'next-intl'; const t = useTranslation('common');

Solution

1. Step 1: Check correct import syntax

   The hook is named useTranslations and imported with curly braces from 'next-intl'.

2. Step 2: Verify usage with namespace

   It requires a namespace string like 'common' to get translations from that section.

3. Final Answer:

   import { useTranslations } from 'next-intl'; const t = useTranslations('common'); -> Option A

4. Quick Check:

   Correct import and call with namespace = import { useTranslations } from 'next-intl'; const t = useTranslations('common'); [OK]

Hint: Always import with braces and pass namespace string [OK]

Common Mistakes:

• Importing without braces
• Calling useTranslations without arguments
• Using wrong hook name useTranslation

3. Given this component using next-intl:

import { useTranslations } from 'next-intl';

export default function Greeting() {
  const t = useTranslations('greeting');
  return <h1>{t('hello')}</h1>;
}

If the messages for locale 'en' are { greeting: { hello: 'Hello, friend!' } }, what will be rendered?

medium

A. An error because 'hello' key is missing

B. <h1>greeting.hello</h1>

C. <h1>Hello, friend!</h1>

D. <h1>Hello</h1>

Solution

1. Step 1: Understand useTranslations usage

   The hook useTranslations('greeting') accesses the 'greeting' namespace in messages.

2. Step 2: Check message key 'hello'

   The key 'hello' inside 'greeting' is 'Hello, friend!'. So t('hello') returns that string.

3. Final Answer:

   <h1>Hello, friend!</h1> -> Option C

4. Quick Check:

   Namespace + key returns correct text = <h1>Hello, friend!</h1> [OK]

Hint: Namespace + key in messages gives displayed text [OK]

Common Mistakes:

• Expecting raw keys instead of translated text
• Assuming missing keys cause errors
• Confusing namespace with key

4. You wrote this code in a Next.js page:

import { NextIntlProvider } from 'next-intl';

export default function Page({ messages }) {
  return (
    <NextIntlProvider messages={messages} locale="en">
      <h1>Welcome</h1>
    </NextIntlProvider>
  );
}

But you get an error: "messages is undefined". What is the likely cause?

medium

A. You forgot to load and pass messages as a prop to the Page component

B. NextIntlProvider does not accept a messages prop

C. Locale must be passed as a number, not a string

D. You must import useTranslations instead of NextIntlProvider

Solution

1. Step 1: Check messages prop usage

   The NextIntlProvider requires a valid messages object passed as a prop.

2. Step 2: Identify cause of undefined

   If messages is undefined, it means the parent or data loader did not supply it properly.

3. Final Answer:

   You forgot to load and pass messages as a prop to the Page component -> Option A

4. Quick Check:

   Missing messages prop causes undefined error [OK]

Hint: Always load and pass messages before using NextIntlProvider [OK]

Common Mistakes:

• Thinking NextIntlProvider doesn't need messages
• Passing locale as number instead of string
• Confusing hooks with provider component

5. You want to support English and Spanish in your Next.js app using next-intl. You have message files:

locales/en.json
locales/es.json

How should you structure your app/layout.tsx to load messages dynamically and provide translations to all pages?

hard

A. Load messages inside each page component instead of layout

B. Import both JSON files statically and pass both to NextIntlProvider at once

C. Use useTranslations in layout to load messages and pass to children

D. Use async function to load messages based on locale, then wrap children with NextIntlProvider passing loaded messages and locale

Solution

1. Step 1: Understand dynamic message loading

   To support multiple locales, load messages dynamically based on the current locale in an async layout or provider.

2. Step 2: Wrap app with NextIntlProvider

   Pass the loaded messages and locale to NextIntlProvider wrapping all children so translations are available app-wide.

3. Final Answer:

   Use async function to load messages based on locale, then wrap children with NextIntlProvider passing loaded messages and locale -> Option D

4. Quick Check:

   Dynamic loading + provider wrapping = Use async function to load messages based on locale, then wrap children with NextIntlProvider passing loaded messages and locale [OK]

Hint: Load messages async by locale, wrap app with NextIntlProvider [OK]

Common Mistakes:

• Importing all locales at once statically
• Loading messages inside pages instead of layout
• Using useTranslations to load messages