Auth0 is a cloud service that provides a set of unified APIs and tools that instantly enables single sign-on and user management for any application, API or IoT device. It's modern identity infrastructure, built for developers. Auth0 provides open source SDKs for all popular platforms, all popular operating systems, all popular devices and all popular programming languages. It allows connections to any identity provider from social to enterprise to custom username/password databases. Auth0 is obsessed with making identity, authentication and authorization simpler for modern applications.
FusionAuth is a single-tenant CIAM solution that deploys on-premises, in your private cloud, or on their fully-managed FusionAuth Cloud. Their JSON REST API provides advanced identity management that is easy for developers to deploy and implement on any platform or framework.
Strata Identity is providing distributed multi-cloud identity solutions to enterprises. Its identity orchestration platform is designed specifically for hybrid and multi-cloud environments that enable users to easily manage distributed identity systems.