OpenID Connect Introduction

OAuth 2.0 is designed only for authorization. It is used for granting access to data and features from one application to another. In OAuth, the client is given a token which it uses to access the data on the resource server, but it doesn’t get to know anything about the user. OAuth was used for authentication as well, but since it was not designed for authentication it was extended further to support authentication.

OpenID Connect is an extension of OAuth. It is a thin layer above OAuth which adds support for authentication.

You may have seen that when you try to login to an app, then the app can prompt you to authenticate using your Facebook or Google account. In this case, the app is probably using OpenID Connect. OpenID Connect allows a range of clients, including web-based, mobile, and JavaScript clients, to request and receive information about authenticated sessions and end-users.