Auth.js is an open-source authentication library designed to integrate seamlessly with modern JavaScript frameworks, providing a flexible and secure authentication experience. It supports various authentication methods, including OAuth (e.g., Google, GitHub), credentials, and WebAuthn, allowing developers to choose the most suitable approach for their applications. Auth.js is compatible with multiple frameworks, such as Next.js, SvelteKit, Express, Qwik, and SolidStart, enabling developers to implement authentication across different platforms. The library offers built-in support for popular databases like Prisma, Drizzle ORM, Supabase, Firebase, and TypeORM, facilitating user data management. Security features include signed cookies, CSRF token validation, and encrypted JSON Web Tokens (JWTs), ensuring robust protection for user data. Auth.js is designed to operate efficiently in serverless environments and provides comprehensive documentation and examples.