Passwordless SMS authentication allows users to log in without entering their password, by generating a one-time use token that is delivered via SMS. In this post, the author builds the iOS front end for a passwordless authentication system using Swift, starting with setting up a new Single View Application and adding a basic interface using Storyboards. The application sends a verification token to the user's phone number when they enter it, which can then be used to authenticate the user. The application uses SwiftRequest to make requests to the Laravel API built in part 1 of the series. Once the authentication is successful, the application moves on to a new view where the user can verify their token and access secure data. The author provides code examples throughout the post and invites readers to share what they've built or ask questions.