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This is documentation for the next SDK version. For up-to-date documentation, see the latest version (SDK 57).

A reference for Babel configuration file.

Babel is used as the JavaScript compiler to transform modern JavaScript (ES6+) into a version compatible with the JavaScript engine on mobile devices.

Each new Expo project created using npx create-expo-app configures Babel automatically and uses babel-preset-expo as the default preset. There is no need to create a babel.config.js file unless you need to customize the Babel configuration.

Create babel.config.js

If your project requires a custom Babel configuration, you need to create the babel.config.js file in your project by following the steps below:

1. Navigate to the root of your project and run the following command inside a terminal. This will generate a babel.config.js file in the root of your project.

2. The babel.config.js file contains the following default configuration:

module.exports = function (api) {
  api.cache(true);
  return {
    presets: ['babel-preset-expo'],
  };
};

3. If you make a change to the babel.config.js file, you need to restart the Metro bundler to apply the changes and use --clear option from Expo CLI to clear the Metro bundler cache:

babel-preset-expo

babel-preset-expo is the default preset used in Expo projects. It extends the default React Native preset (@react-native/babel-preset) and adds support for decorators, tree-shaking web libraries, and loading font icons.