Translate your Expo and React Native app | Internationalization (i18n)

Table of Contents

Why Intlayer over alternatives?

Compared to main solutions like react-native-localize or i18next, Intlayer is a solution that comes with integrated optimizations such as:

Step 1: Install Dependencies

See Application Template on GitHub.

From your React Native project, install the following packages:

npm install intlayer react-intlayernpm install --save-dev react-native-intlayernpx intlayer init

Packages

• intlayer
  The core i18n toolkit for configuration, dictionary content, types generation, and CLI commands.

• react-intlayer
  React integration that provides the context providers and React hooks you’ll use in React Native for obtaining and switching locales.

• react-native-intlayer
  React Native integration that provides the Metro plugin for integrating Intlayer with the React Native bundler.

Step 2: Create an Intlayer Config

In your project root (or anywhere convenient), create an Intlayer config file. It might look like this:

/**
 * If Locales types is not available, try to set moduleResolution to "bundler" in your tsconfig.json
 */
import { Locales, type IntlayerConfig } from "intlayer";

const config: IntlayerConfig = {
  internationalization: {
    locales: [
      Locales.ENGLISH,
      Locales.FRENCH,
      Locales.SPANISH,
      // ... Add any other locales you need
    ],
    defaultLocale: Locales.ENGLISH,
  },
};

export default config;

Within this config, you can:

• Configure your list of supported locales.
• Set a default locale.
• Later, you may add more advanced options (e.g., logs, custom content directories, etc.).
• See the Intlayer configuration docs for more.

Step 3: Add the Metro plugin

Metro is a bundler for React Native. It is the default bundler for React Native projects created with the react-native init command. To use Intlayer with Metro, you need to add the plugin to your metro.config.js file:

const { getDefaultConfig } = require("expo/metro-config");const { configMetroIntlayer } = require("react-native-intlayer/metro");module.exports = (async () => {  const defaultConfig = getDefaultConfig(__dirname);  return await configMetroIntlayer(defaultConfig);})();

Note: configMetroIntlayer is a promise function. Use configMetroIntlayerSync instead if you want to use it synchronously, or avoid IFFE (Immediately Invoked Function Expression). Note: configMetroIntlayerSync does not allow to build intlayer dictionaries on server start

Step 4: Add the Intlayer provider

To keep synchronized the user language across your application, you need to wrap your root component with the IntlayerProvider component from react-intlayer-native.

Make sure to use the provider from react-native-intlayer instead of react-intlayer. The export from react-native-intlayer includes polyfills for the web API.

Also, you need to add the intlayerPolyfill function to your index.js file to ensure that Intlayer can work properly.

import { Stack } from "expo-router";
import { getLocales } from "expo-localization";
import { IntlayerProvider } from "react-native-intlayer";
import { type FC } from "react";

const getDeviceLocale = () => getLocales()[0]?.languageTag;

const RootLayout: FC = () => {
  return (
    <IntlayerProvider defaultLocale={getDeviceLocale()}>
      <Stack>
        <Stack.Screen name="(tabs)" options={{ headerShown: false }} />
      </Stack>
    </IntlayerProvider>
  );
};

export default RootLayout;

Step 5: Declare Your Content

Create content declaration files anywhere in your project (commonly within src/), using any of the extension formats that Intlayer supports:

• .content.json
• .content.ts
• .content.tsx
• .content.js
• .content.jsx
• .content.mjs
• .content.mjx
• .content.cjs
• .content.cjx
• etc.

Example (TypeScript with TSX nodes for React Native):

import { t, type Dictionary } from "intlayer";
import type { ReactNode } from "react";

/**
 * Content dictionary for our "app" domain
 */
import { t, type Dictionary } from "intlayer";

const homeScreenContent = {
  key: "home-screen",
  content: {
    title: t({
      en: "Welcome!",
      fr: "Bienvenue!",
      es: "¡Bienvenido!",
    }),
  },
} satisfies Dictionary;

export default homeScreenContent;

For details on content declarations, see Intlayer’s content docs.

Step 4: Use Intlayer in Your Components

Use the useIntlayer hook in child components to get localized content.

Example

import { Image, StyleSheet, Platform } from "react-native";
import { useIntlayer } from "react-intlayer";
import { HelloWave } from "@/components/HelloWave";
import ParallaxScrollView from "@/components/ParallaxScrollView";
import { ThemedText } from "@/components/ThemedText";
import { ThemedView } from "@/components/ThemedView";
import { type FC } from "react";

const HomeScreen = (): FC => {
  const { title, steps } = useIntlayer("home-screen");

  return (
    <ParallaxScrollView
      headerBackgroundColor={{ light: "#A1CEDC", dark: "#1D3D47" }}
      headerImage={
        <Image
          source={require("@/assets/images/partial-react-logo.png")}
          style={styles.reactLogo}
        />
      }
    >
      <ThemedView style={styles.titleContainer}>
        <ThemedText type="title">{title}</ThemedText>
        <HelloWave />
      </ThemedView>
    </ParallaxScrollView>
  );
};

const styles = StyleSheet.create({
  titleContainer: {
    flexDirection: "row",
    alignItems: "center",
    gap: 8,
  },
});

export default HomeScreen;

When using content.someKey in string-based props (e.g., a button’s title or a Text component’s children), call content.someKey.value to get the actual string.

If your app already exists, you can use the Intlayer Compiler, as well as the extract command, to transform thousands of components in a second.

(Optional) Step 5: Change the App Locale

To switch locales from within your components, you can use the useLocale hook’s setLocale method:

import { type FC } from "react";
import { View, Text, TouchableOpacity, StyleSheet } from "react-native";
import { getLocaleName } from "intlayer";
import { useLocale } from "react-intlayer";

export const LocaleSwitcher: FC = () => {
  const { setLocale, availableLocales } = useLocale();

  return (
    <View style={styles.container}>
      {availableLocales.map((locale) => (
        <TouchableOpacity
          key={locale}
          style={styles.button}
          onPress={() => setLocale(locale)}
        >
          <Text style={styles.text}>{getLocaleName(locale)}</Text>
        </TouchableOpacity>
      ))}
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flexDirection: "row",
    justifyContent: "center",
    alignItems: "center",
    gap: 8,
  },
  button: {
    paddingVertical: 6,
    paddingHorizontal: 12,
    borderRadius: 6,
    backgroundColor: "#ddd",
  },
  text: {
    fontSize: 14,
    fontWeight: "500",
    color: "#333",
  },
});

This triggers a re-render of all components that use Intlayer content, now showing translations for the new locale.

See useLocale docs for more details.

Configure TypeScript (if you use TypeScript)

Intlayer generates type definitions in a hidden folder (by default .intlayer) to improve autocompletion and catch translation errors:

// tsconfig.json{  // ... your existing TS config  "include": [    "src", // your source code    ".intlayer/types/**/*.ts", // <-- ensure the auto-generated types are included    // ... anything else you already include  ],}

This is what enables features like:

• Autocompletion for your dictionary keys.
• Type checking that warns if you access a non-existent key or mismatch the type.

Git Configuration

To avoid committing auto-generated files by Intlayer, add the following to your .gitignore:

# Ignore the files generated by Intlayer.intlayer

VS Code Extension

To improve your development experience with Intlayer, you can install the official Intlayer VS Code Extension.

Install from the VS Code Marketplace

This extension provides:

• Autocompletion for translation keys.
• Real-time error detection for missing translations.
• Inline previews of translated content.
• Quick actions to easily create and update translations.

For more details on how to use the extension, refer to the Intlayer VS Code Extension documentation.

Go Further

• Visual Editor: Use the Intlayer Visual Editor to manage translations visually.
• CMS Integration: You can also externalize and fetch your dictionary content from a CMS.
• CLI Commands: Explore the Intlayer CLI for tasks like extracting translations or checking missing keys.

Enjoy building your React Native apps with fully powered i18n through Intlayer!

Debug

React Native can be less stable than React Web, so pay extra attention to version alignment.

Intlayer primarily targets the Web Intl API; on React Native you must include the appropriate polyfills.

Checklist:

• Use the latest versions of intlayer, react-intlayer, and react-native-intlayer.
• Enable the Intlayer polyfill.
• If you use getLocaleName or other Intl-API-based utilities, import these polyfills early (for example in index.js or App.tsx):

import "intl";import "@formatjs/intl-getcanonicallocales/polyfill";import "@formatjs/intl-locale/polyfill";import "@formatjs/intl-pluralrules/polyfill";import "@formatjs/intl-displaynames/polyfill";import "@formatjs/intl-listformat/polyfill";import "@formatjs/intl-numberformat/polyfill";import "@formatjs/intl-relativetimeformat/polyfill";import "@formatjs/intl-datetimeformat/polyfill";

• Verify your Metro configuration (resolver aliases, asset plugins, tsconfig paths) if modules fail to resolve.