Auth0 is a flexible, drop-in solution to add authentication and authorization services to your applications. Your team and organization can avoid the cost, time, and risk that comes with building your own solution to authenticate and authorize users.
Based on your app's technology, choose one of our SDKs (or call our API), and hook it up to your app. Now each time a user tries to authenticate, Auth0 will verify their identity and send the required information back to your app.
# Free forever
Auth0 is forever free for 7,000 active users.
# Documentation
- Get Started - auth0.com 
- Token best practice - auth0.com
- Authorization - auth0.com
- Auth0 - github.com
# API What we like about Auth0 is the ability to run small communities on a free account together with a very well documented rest api and robust open source client libraries (including passport.js which we use in wiki.
# Research links
- Auth0 or passport? : node - reddit.com
- auth0/passport-auth0: Auth0... - github.com
- node.js - What's the... - stackoverflow.com
- Gmail’s New Login... - techcrunch.com
- JSON Web Token Helper :... - revigniter.com
- Implementing a Persona IdP -... - mozilla.org
- Identity Provider Overview -... - mozilla.org
- What is a Capability URL (... - slideshare.net
- Good Practices for... - w3.org
- tls - A secret in a URL -... - stackexchange.com