FusionAuth
Comprehensive identity and access management (IAM) platform designed to handle authentication, authorization, and user management for applications. Known for its flexibility, scalability, and ease of integration with various types of applications, whether they are web, mobile, or desktop-based, FusionAuth offers features like user management, multi-factor authentication, and single sign-on. It is particularly popular among developers for its extensive documentation and active community support, making it suitable for both small projects and large-scale enterprise applications.