Auth.js is a library for authentication that is open-source and crafted to work effortlessly with contemporary JavaScript frameworks, delivering a secure and adaptable authentication process. It accommodates a range of authentication techniques, such as OAuth options like Google and GitHub, traditional credentials, and WebAuthn, enabling developers to select the best-fitting method for their projects. This library is compatible with various frameworks, including Next.js, SvelteKit, Express, Qwik, and SolidStart, which allows for the implementation of authentication across diverse platforms. Additionally, Auth.js comes with built-in integration for widely-used databases like Prisma, Drizzle ORM, Supabase, Firebase, and TypeORM, making user data management straightforward. To ensure the safety of user information, it features security measures such as signed cookies, validation of CSRF tokens, and encrypted JSON Web Tokens (JWTs). Furthermore, Auth.js is optimized for performance in serverless settings, and it provides thorough documentation along with examples to assist developers. Overall, its versatility and robustness make Auth.js an excellent choice for building secure authentication systems in a variety of applications.