Azure Active Directory vs OAuth2: What are the differences?

Azure Active Directory (AAD) and OAuth2 are both widely used in the field of authentication and authorization. Let's explore the key differences between them.

1. Authentication vs Authorization: AAD is primarily an identity and access management service, focusing on authenticating users and granting them access to resources. On the other hand, OAuth2 is primarily an authorization protocol, focusing on granting access to resources on behalf of a user, without directly authenticating the user.

2. Scope of Usage: AAD is designed specifically for Microsoft Azure services and provides authentication and authorization features for applications running on Azure. OAuth2, on the other hand, is an open standard that can be used by any application or service, regardless of the platform or provider. It is not tied to any specific cloud provider or infrastructure.

3. User Management: AAD provides extensive user management capabilities, allowing organizations to manage users, groups, and roles within their directory. It offers features such as single sign-on, multi-factor authentication, and conditional access policies. OAuth2, on the other hand, does not provide user management capabilities. It relies on the authentication provided by the underlying service or system.

4. Token Handling: AAD issues access tokens to client applications that request access to resources. These tokens are used to verify the identity of the client application and grant it access to the requested resources. OAuth2, on the other hand, uses access tokens as well, but its main focus is on the delegation of access rights from a user to a client application. The access tokens issued by OAuth2 are used to grant access to resources on behalf of the authenticated user.

5. Scalability and Integration: AAD is designed to be highly scalable and integrates seamlessly with other Microsoft Azure services. It provides a unified identity platform for all Azure services and can be used for both cloud-based and on-premises applications. OAuth2, on the other hand, is a protocol that can be implemented by any service or application, making it highly versatile and adaptable to different environments and technologies.

6. Supported Protocols: AAD supports a range of authentication protocols, including OAuth2, OpenID Connect, SAML, and WS-Federation. It provides flexibility in choosing the appropriate protocol based on the requirements of the application. OAuth2, being a protocol itself, supports various grant types that define the interaction between the client application, the resource owner (user), and the authorization server.

In summary, Azure Active Directory (AAD) primarily focuses on authentication and user management for Microsoft Azure services, while OAuth2 is an open standard authorization protocol that can be used by any application or service for granting access to resources on behalf of a user. AAD provides more extensive user management capabilities and integration with Azure services, while OAuth2 is versatile and widely applicable across different platforms and providers.