The document provides a comprehensive guide to building a web application using Next.js and FusionAuth to implement passwordless login via magic links. The application includes public and private pages, requiring users to sign up or log in to view profile information, facilitated by OpenID Connect. The guide outlines prerequisites, explains the concept and benefits of magic links, and offers steps for setting up FusionAuth with Docker Compose, configuring applications, enabling self-service registration, and setting up a SendGrid SMTP server for email communications. It details building the Next.js application, integrating NextAuth.js for authentication, creating a sign-in/sign-out flow, and adding a protected page accessible only to authenticated users. The guide concludes by suggesting enhancements for production readiness, such as offering multiple channels for magic links and customizing the FusionAuth login form.