Expo Docs MCP Server

--- title: Get started with custom builds sidebar_title: Get started description: Learn how to extend EAS Build with custom builds. --- Custom builds allow customizing the build process for your project by running commands before, during, or after the build process. Customized builds can run from EAS CLI or when running builds in a React Native CI/CD pipeline, like with [EAS Workflows](/eas/workflows/get-started/). ## Create a custom build config To get started, create directories and a file named **.eas/build/hello-world.yml** at the same level as **eas.json**. The location and name of both directories are important for EAS Build to identify that a project contains a custom build config. Inside the **hello-world.yml**, you'll write your custom build config. The filename is unimportant; you can name it whatever you want. The only requirement is that the file extension uses **.yml**. Add the following custom build config steps in the file: ```yaml .eas/build/hello-world.yml build: name: Hello World! steps: - run: echo "Hello, world!" # A built-in function (optional) ``` In a real world scenario, you will call a [built-in function](/custom-builds/schema/#built-in-eas-functions) to trigger the build. ## Add `config` property in eas.json To use the custom build config, add the `config` property in **eas.json** under a build profile. Let's create a new [build profile](/build/eas-json/#build-profiles) called `test` under `build` to run the custom config from the **test.yml** file: ```json eas.json { "build": { /* @hide ... */ /* @end */ "test": { "config": "test.yml", }, } ``` If you wish to use separate configs for each platform, you can create separate YAML config files for Android and iOS. For example: ```json eas.json { "build": { /* @hide ... */ /* @end */ "test": { "ios": { "config": "hello-ios.yml", }, "android": { "config": "hello-android.yml", } }, } ``` ## Run a build to test the custom build config To test the custom build config, run the following command: After the build is complete, you can verify that the `echo "Hello World!"` script was executed by checking the logs on the build's detail page. ## Learn more Check out the example repository for more detailed examples: