A Simple Guide for react-intl Integration in React

1. Create a React app

We'll add English and German to a small React app. React Intl renders the messages, while i18nexus handles AI translation and keeps your team's copy in one place.

This example uses Vite and Node.js 22.13+ or 24 LTS. Skip the creation commands if you already have a browser-rendered React app. React Intl 12 requires React 18+.

npm create vite@latest my-app -- --template react
cd my-app
npm install
npm install react-intl@^12

2. Let i18nexus handle your translations

Write your copy once. i18nexus stores your source strings, AI translates them into your project languages, and gives your team a place to review the results. The CLI brings those translations into your app.

To create a new i18nexus project, run this from your app directory:

npx @i18nexus/cli@latest init

For this example, use these choices:

• Sign in or create an account in the browser opened by the CLI.
• Use react-intl as your library. Installed libraries are detected automatically.
• For a new app, choose that you do not have translation JSON yet. Set English (en) as the base language and German (de) as an additional language.
• Use one namespace: common.
• Accept automatic sync in package.json. This installs the CLI locally and adds development and build sync scripts.

When setup finishes, add the project API key printed by the CLI to .env in the app root. Add .env to .gitignore:

I18NEXUS_API_KEY="your_project_api_key"

Add your first two strings

Open the dashboard link printed by the CLI and add these English strings in the common namespace. The key is what your code uses; the value is what your users read.

Expand

• welcome: Welcome to my app!
• greeting: Hello, {name}!

Save each string, then expand its row to see the translations. You can review and edit them in the same place as your source text.

Expand

Prefer working with an AI coding assistant? Choose MCP setup during init, then ask your assistant to create these same strings through i18nexus. The MCP guide explains that workflow. The dashboard remains available for you and your team.

Give AI translation a moment to finish, then download the generated JSON before adding the imports in the next step:

npx i18nexus pull

You should now have src/messages/en/common.json and its German equivalent. These are generated files: make future string changes in i18nexus and let the CLI sync them.

3. Connect React Intl

For this small example, import both generated language files. This keeps switching immediate and avoids a separate loading state. Larger apps can load messages per language as needed.

import {useEffect, useState} from 'react';
import {FormattedMessage, IntlProvider} from 'react-intl';
import en from './messages/en/common.json';
import de from './messages/de/common.json';

const messages = {en, de};
const supportedLocales = ['en', 'de'];

function getInitialLocale() {
  try {
    const saved = localStorage.getItem('locale');
    if (supportedLocales.includes(saved)) return saved;
  } catch {}
  return navigator.languages
    .map(language => language.split('-')[0])
    .find(language => supportedLocales.includes(language)) || 'en';
}

export default function App() {
  const [locale, setLocale] = useState(getInitialLocale);

  useEffect(() => {
    document.documentElement.lang = locale;
    try { localStorage.setItem('locale', locale); } catch {}
  }, [locale]);

  return (
    <IntlProvider locale={locale} defaultLocale="en" messages={messages[locale]}>
      <main>
        <h1><FormattedMessage id="welcome" /></h1>
        <p><FormattedMessage id="greeting" values={{name: 'Sam'}} /></p>
        <select aria-label="Language" value={locale} onChange={event => setLocale(event.target.value)}>
          <option value="en">English</option>
          <option value="de">Deutsch</option>
        </select>
      </main>
    </IntlProvider>
  );
}

The provider supplies the locale and messages to FormattedMessage and useIntl. We start with a saved preference or supported browser language, then save later selections for the next visit.

Keep Vite's src/main.jsx, which already renders App with createRoot. This example is for browser-rendered React; use the dedicated Next.js tutorials for server rendering.

Run npm run dev and try the language switcher. The welcome message and greeting should change together:

EnglishExpand

DeutschExpand

Add plurals when you need them

Add an items string to the common namespace with the ICU value below. Its count argument selects the correct form:

{count, plural, one {# item} other {# items}}

After syncing, render <FormattedMessage id="items" values={{count: 3}} />. Keep the whole sentence together so translations can use the right word order.

Keep translations in sync

The sync script added by the CLI runs i18nexus listen alongside your app. It pulls on startup and updates the generated JSON when strings or translations change in i18nexus. Refresh the page if your app still shows a cached translation.

For deployment, set I18NEXUS_API_KEY in your build environment and run npm run build. The CLI-added prebuild script pulls the latest JSON before compilation. Install dev dependencies in the build stage so the CLI is available. Updates to bundled translations require a new build.

Keep adding source strings in the dashboard or through the i18nexus MCP. Your team can review and refine the AI translations in the same project. React Intl documentation has the details for larger apps.