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Twitter Fastlane Adds Live App Preview from GitHub Pull Requests

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Fastlane, Twitter’s solution to continuous integration and deployment for mobile apps, introduced Device Grid, a new feature aimed to make it possible to live preview changes directly from pull requests in GitHub. Additionally, Fastlane now supports two-factor authentication for iTunes Connect, and improved support for Android APK files.

Fastlane Device Grid attempts to make it easier for developers to live preview app changes from a GitHub pull request, without requiring them to manually build and install the app. Device Grid relies on Danger for integration with GitHub’s PR system, and on, a service that provides web-based iOS simulators and Android emulators, to stream apps directly from the browser.

Fastlane Device Grid can be configured to automatically create a build of your app for the iOS simulator target and upload it to The following snippet is how you can configure Fastlane to build and upload an app to

desc "Build your app and upload it to Appetize to stream it in your browser"
lane :upload_to_appetize do
    xcodebuild: {
      workspace: "YourApp.xcworkspace",
      scheme: "YourScheme"

Alternatively, developers can manually generate their apps and download them to

Fastlane Device Grid also supports the use of deep links to launch the app at a specific point, so reviewers can directly access the parts they should review. Developers can specify the deep link to jump to by adding it at the bottom of the PR-body, e.g.:


Another feature that will be useful to many developers is Fastlane’s support for two-factor authentication when accessing iTunes Connect. Two-factor authentication has been recently enabled by Apple to verify a developer’s identity using their mobile phone and thus provide greater security and control.

On the usability front, Fastlane can now be installed from Twitter’s Fabric app for Mac, which will take care of dependencies and any previously installed version.

As mentioned, Fastlane now provides improved support for APK files. Specifically, APK expansion files can be uploaded to Google Play and APK can be promoted between tracks, thus allowing developers to promote beta builds to production without submitting the APK again.

Originally developed by Felix Krause, Fastlane aims to provide “a fully working Continuous Deployment process” that can be triggered by running a single command. Eight months ago, Twitter announced Fastlane’s inclusion within its mobile development platform Fabric, which is a modular set of development tools such as remote crash reporting, beta management, etc., for iOS, Android, and other platforms.

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