At the point when a site needs to utilize the administrations of another, for example, Bitly presenting on your Twitter stream—rather than requesting that you share your secret key, they should utilize a convention called OAuth.

What is OAuth?
It's critical to see how a program, site, or application may validate you as a client – so they have the correct authorizations? Have you conceded them some kind of method for confirming your identity – and getting to information for your sake? OAuth streamlines this procedure: yet even with robotization, dependably know about how an individual or organization uses your information.

Definition of OAuth
What is OAuth? How OAuth works? OAuth (Open Authentication) is a unique access token based authentication over the internet. OAuth is often used by tech giants to authorize third-party apps to provide access over restricted resources that resides in a giant’s ecosystem without revealing user’s login credentials. OAuth has a large number of scopes or actions that can be requested by third-party apps through APIs hence it is used for easy login in software applications.

Why OAuth was introduced?
OAuth was introduced because there was a need for easy sign in that could be used as a common sign in option for lots of apps. All the information required to create a user account is usually present in social media accounts of users so OAuth was developed with the aim to share this information with apps after getting permissions from the user.

When OAuth was launched?
In 73rd Internet Engineering Task Force (IETF) meeting in Minneapolis in November 2008, OAuth was introduced to discuss further standardization work to be done. The event was well attended and addressed wide support inside IETF and outsider’s chartering groups. After going through a long development cycle, the OAuth 2.0 Framework and Bearer Token Usage were finally published in October 2012. Although OAuth 2.0 has some limitations like it is not backwards compatible with OAuth 1.0 yet it is being used by Google, Facebook, Twitter, Microsoft’s Azure active directory and many others. OAuth 2.0 provides authorization flows for web apps, desktop apps, mobile phones, and smart devices.

How does OAuth work?
OAuth uses secret keys and access tokens that are uniquely assigned to users for using OAuth for an app developer need to register software applications with the social media platform or the tech giant whose database they want to access. The developer needs to go on developers’ section of the social media platform and register the web app with URL on which it is deployed, then he/she will get the secret keys and access tokens.

OAuth workflow has the following 5 itineraries which are used to authenticate users:

User

A visitor who wants easy access over apps without the hassle of creating a new account.

Browser

A web browser is a simple tool which is being used by the user to access the software application, here that is called client.

Client

The client is a software application which can be a web app, desktop app, mobile phone app or a smart device.

Authorization Server

Authorization Server authorizes user and client (software application) from OAuth API provider.

Resource Server

When user and client (software application) are authenticated then the user can request for restricted resources through a client (software application) from OAuth API provider.

Workflow of OAuth: Read the full article here: https://www.decipherzone.com/blog-detail/What-is-OAuth-and-how-it-works-