OAuth (Open Authorization) is an open-standard protocol that enables secure delegated access to resources without revealing user credentials. OAuth allows users to grant third-party applications limited access to their resources (such as files, data, or other services) on another platform, without sharing their username and password.

OAuth works by allowing a user to authorize one service (the client) to access resources hosted by another service (the resource server) on their behalf. Instead of sharing login credentials, OAuth uses tokens—which are temporary, limited in scope, and revocable at any time. This provides a layer of security, as the client never sees or stores the user's sensitive credentials.

The OAuth process involves four main roles:

Resource Owner: The user who owns the data or resource and wants to grant access to it.
Client: The application requesting access to the resource.
Authorization Server: The server that issues tokens after authenticating and authorizing the client.
Resource Server: The server hosting the resource, which validates the token and allows access.
The process generally works as follows:

The client requests authorization from the resource owner.
If the owner consents, the authorization server issues an access token to the client.
The client uses the token to make authorized requests to the resource server.
One of the common uses of OAuth is allowing users to log into websites using credentials from another platform, like Google, Facebook, or GitHub, without needing to create new accounts.

OAuth 2.0, the most widely used version, is implemented across various services, including social media platforms, cloud services, and API-based applications. It supports single sign-on (SSO) and is a key enabler for modern, scalable, and secure web and mobile applications.

This decentralized and token-based approach enhances security while providing convenience for users and developers alike.