Fastlane

fastlane is an open-source Ruby tool that automates building, signing, testing and releasing native apps. Steps are actions (build_app, upload_to_testflight, match), grouped into lanes in a Fastfile, and run the same way on a laptop and in CI. In React Native it is used for bare projects and for Expo projects built without EAS (on the native projects generated by npx expo prebuild); EAS Build and EAS Submit are Expo's cloud alternative.

Details

What It Automates

Task	Actions
iOS code signing	match: certificates and profiles in a private encrypted git repo or cloud storage, shared by the team and CI
Build	build_app (gym) for iOS, gradle for Android
Versioning	increment_build_number, increment_version_code (plugin)
Beta distribution	upload_to_testflight, upload_to_play_store(track: 'internal'), Firebase App Distribution (plugin)
Store release	upload_to_app_store (deliver), upload_to_play_store (supply), metadata and release notes
Screenshots	capture_screenshots (snapshot) across devices and languages

Fastlane vs EAS

	fastlane	EAS Build / Submit
Runs on	Your machines or CI (iOS builds need macOS)	Expo's cloud, or locally with --local
Signing	match or manual	Credentials managed by EAS
Fits	Any native project, full control	Expo and bare projects; paid tiers for more builds

Example

lane :beta_ios do
  match(type: "appstore")           # Fetch the certificate and profile
  increment_build_number(xcodeproj: "ios/MyApp.xcodeproj")
  build_app(workspace: "ios/MyApp.xcworkspace", scheme: "MyApp")
  upload_to_testflight
end

lane :beta_android do
  # Play rejects a second upload with the same versionCode
  increment_version_code(gradle_file_path: "android/app/build.gradle") # plugin
  gradle(task: "clean bundleRelease", project_dir: "android")
  upload_to_play_store(track: "internal", aab: "android/app/build/outputs/bundle/release/app-release.aab")
end

Follow-up Questions

• How does CI get the certificates? match(readonly: true) fetches them from the match repository and decrypts them with MATCH_PASSWORD; repository access and the App Store Connect API key (for uploads) are CI secrets.
• Why do iOS builds need macOS? Xcode runs only on macOS, hence macOS runners or EAS Build.

Common Mistakes

• Not bumping the build number or versionCode: the store rejects a build with a number it already has.
• Committing certificates or keystore passwords instead of using match and CI secrets.

See Also

• Publishing and Distribution
• CI/CD