OAuth 2.0 is an authorization framework that allows third-party applications to securely access a user's resources (such as accounts or data) on another service without sharing passwords. It is widely used for enabling single sign-on (SSO) and providing secure, delegated access to APIs, with the following benefits. * **Secure Authorization** - OAuth 2.0 allows users to grant limited access to their data without exposing their credentials, reducing the risk of unauthorized access. * **Granular Permissions** - Applications can request specific scopes of access, such as read-only or write permissions, providing fine-grained control over data sharing. * **Token-Based Authentication** - OAuth 2.0 uses access tokens, which are temporary and revocable, reducing security risks associated with long-term credentials. * **Scalable and Flexible** - It supports a variety of client types (e.g., web apps, mobile apps, and IoT devices) and use cases, including single sign-on and third-party integrations. * **No Password Sharing** - Users authenticate with the authorization server, and the application receives a token instead of the user's password, enhancing security. * **Industry Standard** - OAuth 2.0 is widely adopted and supported by major platforms like Google, Facebook, GitHub, and Microsoft, ensuring compatibility with modern web and mobile applications. * **Refresh Tokens** - Provides a mechanism to renew access tokens without requiring the user to log in again, improving user experience and session management. OAuth 2.0 has become the industry standard for secure, token-based authorization, enabling applications to access user data without compromising privacy. It is ideal for SSO, API security, and third-party integrations, offering scalability, flexibility, and enhanced security for different types of applications. There are some complaints that OAuth 2.0 has become very broad and bloated, but it has reached mainstream adoption and will define authentication and authorization across the API landscape for many years to come. When you have wide variety of resources, with many end-users of those resources, applying OAuth 2.0 for API authentication and authorization makes sense.