--- title: "REST API vs RESTful API: Architecture and Constraints Explained" description: "What separates REST API from RESTful API, and what statelessness, uniform interface, client-server separation, cacheability, and layered systems actually mean in practice." author: "Mohammad Abu Mattar" canonical: https://mkabumattar.com/blog/post/rest-api-vs-restful-api-architecture-and-constraints-explained --- # REST API vs RESTful API: Architecture and Constraints Explained ## Introduction REST API and RESTful API get used interchangeably, but they aren't quite the same thing. This post covers the difference, REST's constraints, and what they mean for how you design an API. ## What is the Difference Between REST API and RESTful API? REST API is the general term for any API that follows REST's principles. RESTful API refers to an API that strictly adheres to all of REST's constraints. In practice, most APIs called "REST" only follow some of those constraints, which is why the two terms end up being used loosely. ## Why is REST API Called RESTful API? RESTful APIs strictly follow REST's principles, which is what makes them scalable, reliable, and easy to integrate with other systems. ## What is REST and Explaining RESTful APIs? - **Statelessness:** RESTful APIs are completely stateless. Each client request carries all the information the server needs to process it, so the server doesn't have to store session-specific data. This is what makes them scalable and reliable under load. - **Uniform Interface:** RESTful APIs use a standard, consistent interface: HTTP methods like GET, POST, PUT, and DELETE to interact with resources, and unique URIs (Uniform Resource Identifiers) to identify them. - **Client-Server Architecture:** REST separates the client from the server. The client handles the user interface and experience; the server handles data storage and processing. Each side can evolve independently as long as the interface between them stays the same. - **Cacheability:** RESTful APIs work with HTTP caching. By specifying cache-related headers, responses can be marked cacheable, which improves performance and reduces server load. - **Layered System:** REST allows multiple layers, such as load balancers and firewalls, to sit between the client and the server. This layered architecture supports scalability, security, and flexibility. ## Examples of REST API and RESTful APIs Take an e-commerce application. Here are two scenarios for retrieving product information: ### REST API Example: - Endpoint: **`GET /products`** - Description: Retrieves a list of all products. - Response: A JSON array of product objects. ### RESTful API Example: - Endpoint: **`GET /products/{id}`** - Description: Retrieves a specific product by its ID. - Response: A JSON object representing that product. Both examples follow REST's principles by using the proper HTTP method (GET) and providing the necessary resource identifiers (URL paths). ## Difference Between Web API and RESTful Services Web API is the umbrella term for any interface that lets different software systems communicate over the web. RESTful services are one architectural style under that umbrella. While RESTful services strictly follow REST's principles, not all web APIs do. Some use other approaches like SOAP, XML-RPC, or GraphQL. ## Conclusion Understanding the difference between REST API and RESTful API comes down to how strictly the API follows REST's constraints. Applying those constraints (statelessness, uniform interface, client-server separation, cacheability, layered systems) is what makes an API scalable and easier to maintain over time. For more on this, see [RESTful API vs. GraphQL: Which API is the Right Choice for Your Project?](/blog/post/restful-api-vs-graphql-which-api-is-the-right-choice-for-your-project). ## References 1. Fielding, Roy T. "Architectural Styles and the Design of Network-based Software Architectures." Doctoral dissertation, University of California, Irvine, 2000. (The origin of REST.), [https://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm](https://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm) 2. "What is REST?" - REST API Tutorial.), [https://restfulapi.net/](https://restfulapi.net/) 3. "Understanding RESTful APIs" - Smashing Magazine.), [https://www.smashingmagazine.com/2018/01/understanding-restful-apis/](https://www.smashingmagazine.com/2018/01/understanding-restful-apis/) 4. "REST API Design Rulebook" - Mark Masse. O'Reilly Media.), [Link to a reputable source for the book or summary] 5. "HTTP Methods for RESTful Services" - REST API Tutorial.), [https://restfulapi.net/http-methods/](https://restfulapi.net/http-methods/) 6. "Statelessness in REST APIs" - GeeksforGeeks.), [https://www.geeksforgeeks.org/statelessness-in-rest-apis/](https://www.geeksforgeeks.org/statelessness-in-rest-apis/) 7. "Uniform Interface Constraint in REST" - REST API Tutorial.), [https://restfulapi.net/uniform-interface/](https://restfulapi.net/uniform-interface/) 8. "Client-Server Architecture" - MDN Web Docs.), [https://developer.mozilla.org/en-US/docs/Web/HTTP/Overview#client-server_architecture](https://developer.mozilla.org/en-US/docs/Web/HTTP/Overview#client-server_architecture) 9. "HTTP Caching" - MDN Web Docs.), [https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching](https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching) 10. "Layered System Constraint in REST" - REST API Tutorial.), [https://restfulapi.net/layered-system/](https://restfulapi.net/layered-system/) 11. "What is a Web API?" - MuleSoft.), [https://www.mulesoft.com/resources/api/what-is-a-web-api](https://www.mulesoft.com/resources/api/what-is-a-web-api) 12. "API Design Best Practices" - Swagger/OpenAPI.), [https://swagger.io/resources/articles/best-practices-in-api-design/](https://swagger.io/resources/articles/best-practices-in-api-design/) 13. "Richardson Maturity Model" (Steps toward the glory of REST.), [https://martinfowler.com/articles/richardsonMaturityModel.html](https://martinfowler.com/articles/richardsonMaturityModel.html)