FusionAuth is described as 'Auth for any app. Get everything you need for secure registration and user management in minutes. Single-tenant, on-prem or private cloud, custom emails with localization, social login, and more' and is a identity management tool in the security & privacy category. There are more than 50 alternatives to FusionAuth for a variety of platforms, including Web-based, SaaS, Self-Hosted, Linux and Mac apps. The best FusionAuth alternative is Keycloak, which is both free and Open Source. Other great apps like FusionAuth are AuthKit, authentik, Hanko and Stack Auth.