Expo Docs MCP Server

--- title: babel.config.js description: 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`](https://github.com/expo/expo/tree/main/packages/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: ```js babel.config.js 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`](https://github.com/expo/expo/tree/main/packages/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.