OpenShift
Google App Engine
Salesforce Platform
Dokku
Heroku
Google Cloud Functions
Microsoft Azure
Kubernetes
OAuth2
Auth0
Spring Security
Devise
JSON Web Token
Firebase Authentication
Amazon Cognito
OmniAuth
OpenShift
OAuth2Google App Engine - A powerful platform to build web and mobile apps that scale automatically.
Auth0 - Auth0 is a program for people to get authentication and authorization services for their own business use.
Salesforce Platform - Salesforce Platform is a comprehensive PaaS solution that paves the way for the developers to test, build, and mitigate the issues in the cloud application before the final deployment.
Spring Security - The Spring portfolio has many projects, including Spring Framework, Spring IO Platform, Spring Cloud, Spring Boot, Spring Data, Spring Security...
Dokku - Docker powered mini-Heroku in around 100 lines of Bash
Devise - Flexible authentication solution for Rails with Warden.