Understanding OAuth 2.0 Flow: Complete Diagram and Implementation Guide

OAuth 2.0 is the industry-standard authorization framework that lets third-party apps access user resources via scoped access tokens instead of passwords, formalized in RFC 6749. The article explains key roles (Resource Owner, Client, Authorization Server, Resource Server) and details the Authorization Code flow—the most secure grant type for server-side apps—covering front-channel redirects, back-channel token exchange, and CSRF protection via the state parameter.