In this article, several popular authorization models are discussed to help choose the right fit for your SaaS app's security and user management. The most basic form of access control is using roles, which can be suitable if users only need to be separated into broad categories with minimal overlap between roles. However, role-based systems can be too restrictive in smaller companies or startups where roles are more fluid. An alternative approach is to use roles and permissions, which adds granularity by defining specific actions users can perform within the app. This model is useful when there is a significant overlap in access rights between different roles but some variations. Another option is attribute-based access control (ABAC), which decides access based on user attributes or resource attributes, creating a more flexible and dynamic system. Relationship-based access control (ReBAC) focuses on the relationships between users, resources, and other entities, often used in social media platforms, collaboration tools, or enterprise systems. Policies are rule-based models that define access control using logical statements or expressions, allowing for fine-grained, dynamic, and customizable access control. Finally, Fine-Grained Authorization (FGA) combines all these approaches, offering a comprehensive, flexible, and fine-grained authorization model suitable for complex applications with diverse and constantly changing access control requirements.