Azure Active Directory (Azure AD) is a cloud-based identity and access management service provided by Microsoft, offering single sign-on functionality to users in an organization. On the other hand, Casbin is an open-source access control library that implements the RBAC (Role-Based Access Control) model for authorization.

1. Architecture: Azure Active Directory is a cloud-based service that provides identity-based access control for applications and services, integrating with various Microsoft products. In contrast, Casbin is a lightweight and flexible access control library that can be integrated into any application or framework to manage authorization policies.

2. Scope: Azure Active Directory primarily focuses on providing identity management and single sign-on capabilities for users to access various resources within the Microsoft ecosystem. On the contrary, Casbin is specifically designed for role-based access control policies, allowing developers to define and enforce fine-grained access control rules in their applications.

3. Customization: Azure Active Directory offers a set of predefined roles and permissions that can be assigned to users for accessing different resources based on their roles. In contrast, Casbin allows developers to define custom access control policies, enabling more granular control over authorization decisions within an application.

4. Integration: Azure Active Directory seamlessly integrates with various Microsoft services and applications, providing centralized identity management and access control across the organization's ecosystem. Casbin, on the other hand, is a standalone library that can be integrated into any application or framework, regardless of the technology stack being used.

5. Deployment: Azure Active Directory is a managed service provided by Microsoft, available as a subscription-based offering in the Azure cloud platform. In contrast, Casbin is an open-source library that can be downloaded and deployed on-premises or in the cloud, giving developers full control over the implementation and customization of access control policies.

In Summary, Azure Active Directory focuses on identity management and single sign-on, while Casbin is a flexible access control library specifically designed for implementing role-based access control policies in applications.