How to: Authentication and OAuth
* [API Guard](https://github.com/Gokul595/api_guard) - JWT authentication solution for Rails APIs.
* [Authentication Zero](https://github.com/lazaronixon/authentication-zero) - An authentication system generator for Rails applications.
* [Authlogic](https://github.com/binarylogic/authlogic) - Authlogic is a clean, simple, and unobtrusive ruby authentication solution.
* [Clearance](https://github.com/thoughtbot/clearance) - Small and simple email & password based authentication for Rails.
* [Devise](https://github.com/heartcombo/devise) - A flexible authentication solution for Rails based on Warden.
* [JWT](https://github.com/jwt/ruby-jwt) - JSON Web Token implementation in Ruby.
* [Monban](https://github.com/halogenandtoast/monban) - A very simple and extensible user authentication library for rails.
* [OmniAuth](https://github.com/omniauth/omniauth) - A library that standardizes multi-provider authentication utilizing Rack middleware.
* [Rodauth](https://github.com/jeremyevans/rodauth) - Authentication and account management framework for Rack applications.
* [Sorcery](https://github.com/Sorcery/sorcery) - A stripped-down, bare-bones authentication library for Rails.
* [warden](https://github.com/hassox/warden) - General Rack Authentication Framework.
* OAuth:
  * [Doorkeeper](https://github.com/doorkeeper-gem/doorkeeper) - An OAuth2 provider for Rails.
  * [OAuth2](https://github.com/intridea/oauth2) - A Ruby wrapper for the OAuth 2.0 protocol.
  * [Rodauth-Oauth](https://gitlab.com/honeyryderchuck/rodauth-oauth) - A rodauth OAuth and OpenID provider plugin.