OAuth 2.0 (short for "Open Authorization") is the industry-standard protocol for authorization. Generally, the OAuth protocol provides a way for resource owners to provide a client [application] with secure delegated access to server resources.
OAuth framework specifies several grant types for different use cases. Some of the most common OAuth grant types are:
Doorkeeper is an OAuth 2 provider for Ruby on Rails / Grape.
The reliable YouTube API Ruby client
OAuth 2.0 Server & Client Library. Both Bearer and MAC token type are supported.
An abstract OAuth2 strategy for OmniAuth.
Redd is a batteries-included API wrapper for reddit.
An example OAuth 2 provider application using the Doorkeeper gem, Rails and Devise
Vkontakte OAuth2 Strategy for OmniAuth
A basic OAuth2 plugin for use with Discourse
OAuth 2 authentication with the Azure ActiveDirectory V2 API.
Support (and manage) Authentication with multiple OmniAuth providers in your Rails application
Self-hosting SSO Portal, support Oauth2, Open ID Connect and SAML 2.0
OAuth2 strategy for Okta
Flexible, ORM-agnostic, fully customizable and simple OAuth2 provider for Grape API
Translation files for Doorkeeper OAuth 2 provider
Created by IETF OAuth Working Group
Released October 2012