Source: https://docs.expo.dev/versions/latest/config/babel

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babel.config.js

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A reference for Babel configuration file.

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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:

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.

Terminal

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- npx expo customize babel.config.js

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

babel.config.js

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

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:

Terminal

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- npx expo start --clear

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.