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iOS build process

This page describes the process of building iOS projects with EAS Build. You may want to read this if you are interested in the implementation details of the build service.

Build Process

Let's take a closer look at the steps for building iOS projects with EAS Build. We'll first run some steps on your local machine to prepare the project and then we'll actually build the project on a remote service.

The first phase happens on your computer. EAS CLI is in charge of completing the following steps:
  1. If cli.requireCommit is set to true in eas.json, check if the git index is clean - this means that there aren't any uncommitted changes. If it's not clean, EAS CLI will provide an option to commit local changes for you or abort the build process.
  2. Prepare the credentials needed for the build.
    • Depending on the value of builds.ios.PROFILE_NAME.credentialsSource, the credentials are obtained from either the local credentials.json file or from the EAS servers. If the remote mode is selected but no credentials exist yet, you're offered to generate them.
  3. Bare projects require an additional step: check whether the Xcode project is configured to be buildable on the EAS servers (i.e. ensure the correct bundle identifier and Apple Team ID are set).
  4. Create the tarball containing a copy of the repository. Actual behavior depends on the VCS workflow you are using. Learn more here.
  5. Upload the project tarball to a private AWS S3 bucket and send the build request to EAS Build.

In this next phase, this is what happens when EAS Build picks up your request:
  1. Create a new macOS VM for the build.
    • Every build gets its own fresh macOS VM with all build tools installed there (Xcode, Fastlane, and so on).
  2. Download the project tarball from a private AWS S3 bucket and unpack it.
  3. Create .npmrc if NPM_TOKEN is set. (Learn more.)
  4. Run the eas-build-pre-install script from package.json if defined.
  5. Run npm install in the project root (or yarn install if yarn.lock exists).
  6. Run expo doctor to diagnose potential issues with your project configuration.
  7. Restore the credentials
    • Create a new keychain.
    • Import the Distribution Certificate into the keychain.
    • Write the Provisioning Profile to the ~/Library/MobileDevice/Provisioning Profiles directory.
    • Verify that the Distribution Certificate and Provisioning Profile match (every Provisioning Profile is assigned to a particular Distribution Certificate and cannot be used for building the iOS with any other certificate).
  8. Managed projects require an additional step: Run expo prebuild to convert the project to a bare one.
  9. Restore a previously saved cache identified by the cache.key value in the build profile. (Learn more.)
  10. Run pod install in the ios directory inside your project.
  11. Run the eas-build-post-install script from package.json if defined.
  12. Update the Xcode project with the ID of the Provisioning Profile.
  13. Create Gymfile in the ios directory if it does not already exist (check out the Default Gymfile section).
  14. Run fastlane gym in the ios directory.
  15. Run the eas-build-pre-upload-artifacts script from package.json if defined.
  16. Store a cache of files and directories defined in the build profile. Podfile.lock is cached by default. Subsequent builds will restore this cache. (Learn more.)
  17. Upload the build artifact to a private AWS S3 bucket.
    • The artifact path can be configured in eas.json at builds.ios.PROFILE_NAME.artifactPath. It defaults to ios/build/App.ipa. You can specify a glob-like pattern for artifactPath. We're using the fast-glob package under the hood.

We're using Fastlane for building iOS projects. To be more precise, we're using the fastlane gym command (see the Fastlane docs to learn more). This command allows you to declare the build configuration in Gymfile.
EAS Build can use your own Gymfile. All you need to do is to place this file in the ios directory.

If the ios/Gymfile file doesn't exist, the iOS builder creates a default one. It looks something like this:


  method: "app-store",
  provisioningProfiles: {
    "com.expo.eas.builds.test.application" => "dd83ed9c-4f89-462e-b901-60ae7fe6d737"

export_xcargs "OTHER_CODE_SIGN_FLAGS=\"--keychain /tmp/path/to/keychain\""