Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
Okta - Enterprise-grade identity management for all your apps, users & devices
Firebase Authentication - Application and Data, Application Utilities, and User Management and Authentication
OmniAuth - OmniAuth is a flexible authentication system utilizing Rack middleware.
jQuery - The Write Less, Do More, JavaScript Library.
Spring Security - The Spring portfolio has many projects, including Spring Framework, Spring IO Platform, Spring Cloud, Spring Boot, Spring Data, Spring Security...