Expo Docs MCP Server

--- title: Expo Modules API: Get started sidebar_title: Get started description: Learn about getting started with Expo modules API. --- **There are two ways to get started with the Expo Modules API:** you can either initialize a new module from scratch or add the Expo Modules API to an existing module. This guide will walk you through creating a new module from scratch, and the [Integrating in an existing library](/modules/existing-library) covers the latter. The two recommended flows to create a new module with Expo Modules API: - [Add a new module to an existing Expo application](#adding-a-new-module-to-an-existing-application), and use it to test and develop your module. - [Create a new module in isolation with a generated example project](#creating-a-new-module-with-an-example-project) if you want to reuse it in multiple projects or publish it to npm. Both of these flows are covered in the next sections. ## Add a new module to an existing application ### Create the local Expo module Navigate to your project directory (the one that contains the **package.json** file) and run the following command. This is the recommended way to create a local Expo module. Then, if your project doesn't have native projects generated (**android** and **ios** directories), run the following command, otherwise skip this command: You can provide a meaningful module name in the CLI prompt. For the rest of the prompts, you can also accept the default suggestions. > **Note**: If you have a pre-existing **ios** directory in your project's root which was created using `npx expo prebuild`, you must reinstall the pods: > > <br /> > ### Use the local module Import the local module in your application, for example in **App.js** or **App.tsx** or **app/index.tsx**: ```tsx App.tsx /* @hide ...*/ /* @end */ return ( <View style={styles.container}> /* @info In the component, return the result of the native method. */ <Text>{MyModule.hello()}</Text> /* @end */ </View> ); } ``` Start the development sever in your terminal so that when you edit the native module and build the app in the next step, the changes will be reflected in the app: Congratulations! You have created a local Expo module. You can now start working on it. > **info** **Tip**: You can also use absolute import paths [by applying these configuration changes](https://expo.fyi/absolute-path-expo-modules.md). ### Edit the module To develop and test your module locally, let's use Android Studio and Xcode for Android and iOS. #### Android 1. Open the **android** directory (that is generated by `npx expo prebuild` in step 1) from your project in Android Studio. It may take a while for Gradle to finish syncing the native directory project. 2. Once the project is synced, open **modules/my-module/android/src/main/java/expo/modules/mymodule/MyModule.kt** file. 3. Change `hello` function to return a different string, such as "Hello world! 🌎🤖" and save the file. 4. Build the app by clicking **Run 'app'** button from top menu bar and you will see the changes on the screen. You have to repeat the build step anytime you make a change to the native code to the changes. #### iOS 1. Open the **ios** directory (that is generated by `npx expo prebuild` in step 1) from your project in Xcode by running `xed ios` command. 2. Under **Pods** > **Development Pods** > **MyModule**, open **MyModule.swift** file. 3. Change `hello` function to return a different string, such as "Hello world! 🌎🍎" and save the file. 4. Build your app by clicking **Run** button from top menu bar or press <kbd>⌘ Cmd</kbd> + <kbd>R</kbd>, you will see the changes on the screen. You have to repeat the build step anytime you make a change to the native code to the changes. > **info** **Tip**: Use `npx pod-install` to reinstall the pods if you add new native files to the module or when you modify **expo-module.config.json**. > **Note**: There are also other flows for working on an Expo module in parallel with your application. For example, you can use a monorepo or publish to npm, as described in the [How to use a standalone Expo module](/modules/use-standalone-expo-module-in-your-project) guide. ## Create a new module with an example project ### Create the Expo module To create a new Expo module from scratch, run the `create-expo-module` script as shown below. The script will ask you a few questions and then generate the native Expo module along with the example app for Android and iOS that uses your new module. ### Open the module and start the development server Navigate to the module directory and then open the Android and/or iOS example project by running the following commands: Go to **example** directory and start the development sever in your terminal so that when you edit the native module and build the app in the next step, the changes will be reflected in the app: > **Note:** If you're using Windows, you can open the example project by opening the **android** directory in Android Studio, but you cannot open the iOS project files. ### Edit the module #### Android 1. Open **my-module/android/src/main/java/expo/modules/mymodule/MyModule.kt** file. 2. Change `hello` function to return a different string, such as "Hello world! 🌎🤖" and save the file. 3. Build the app by clicking **Run 'app'** button from top menu bar and you will see the changes on the screen. You have to repeat the build step anytime you make a change to the native code to the changes. #### iOS 1. Under **Pods** > **Development Pods** > **MyModule**, open **MyModule.swift** file. 2. Change `hello` function to return a different string, such as "Hello world! 🌎🍎" and save the file. 3. Build your app by clicking **Run** button from top menu bar or press <kbd>⌘ Cmd</kbd> + <kbd>R</kbd>, you will see the changes on the screen. You have to repeat the build step anytime you make a change to the native code to the changes. > **info** **Tip**: Use `npx pod-install` to reinstall the pods if you add new native files to the module or when you modify **expo-module.config.json**. ## Next steps Now that you have learned how to initialize a module and make simple changes to it, you can continue to a tutorial or dive right into the API reference.