In the evolving landscape of web development, secure and efficient user authentication is paramount, prompting the use of OAuth Single Sign-On (SSO) to streamline login processes. This method allows users to access applications using existing accounts from services like Google or GitHub, reducing the need to remember multiple credentials. The text provides a detailed tutorial on implementing OAuth SSO in a Next.js project using JSON Web Tokens (JWT) and the app router, specifically focusing on GitHub SSO. It guides through setting up a project, creating a GitHub OAuth app, configuring environment variables, and implementing sign-in and callback processes with JWT for authentication. Furthermore, it introduces Clerk, a user management platform, as a more comprehensive solution for handling OAuth authentication, offering support for various providers and additional features like passwordless sign-in. The text also addresses the limitations of a basic OAuth setup, such as the lack of CSRF protection and refresh tokens, suggesting Clerk as a robust alternative for scalable and secure user authentication.