What is a REST API? Understanding How RESTful Web Services Work
Learn what a REST API is, how it works, and why it's widely used in modern web development. Discover the key features of REST APIs, how they compare to SOAP, and why developers prefer them.
In today’s interconnected world, applications rarely operate in isolation. Whether you're building a mobile app, a web platform, or a microservice, the need to exchange data between systems is inevitable. This is where APIs—Application Programming Interfaces—come into play.
One of the most popular approaches to designing APIs is REST, short for Representational State Transfer. In this lesson, you'll gain a clear understanding of what a REST API is, how it functions, why it's favored by developers, and how it compares to older technologies like SOAP. We’ll also briefly look at alternative API architectures, setting the foundation for building powerful web services using Symfony 6.
What is a REST API?
A REST API is a standardized way for two software systems to communicate over the internet using the HTTP protocol. It defines a set of constraints and conventions that guide how requests and responses should be structured.
In simple terms, REST allows a client (like a mobile app or frontend interface) to retrieve or send data to a server. It’s often used to expose data and services in a way that other systems can easily consume and interact with.
Key Characteristics of REST APIs
Stateless Communication
One of REST’s core principles is statelessness. Every request made by a client must contain all the information needed to understand and process the request. The server doesn’t retain any context or session data between requests.
This design makes REST APIs easier to scale because the server doesn’t need to track client state, which reduces memory usage and complexity.
Uniform Interface
REST APIs follow a consistent and predictable structure. This includes using standard HTTP methods like:
GETto retrieve dataPOSTto create dataPUTto update dataDELETEto remove data
By maintaining a uniform interface, REST APIs simplify development and improve client-server interactions.
Resource-Based Architecture
In REST, data is treated as resources—each resource (like a user, product, or article) has a unique URL. Clients interact with these resources using the standard HTTP methods mentioned above.
Use of Standard Data Formats
REST APIs typically use lightweight formats like JSON for request and response bodies. JSON is easy to read and write, widely supported, and more efficient than older formats like XML.
REST vs SOAP: What’s the Difference?
Before REST gained widespread adoption, another protocol called SOAP (Simple Object Access Protocol) was commonly used to exchange structured data between systems. While SOAP is still in use in some enterprise environments, it has largely been replaced by REST in modern web development.
| Feature | REST API | SOAP API |
|---|---|---|
| Data Format | JSON (commonly) | XML |
| Coupling | Loosely Coupled | Tightly Coupled |
| Learning Curve | Easier | Steeper |
| Flexibility | High | Moderate |
| Performance | Faster (lightweight) | Slower (verbose XML) |
| Protocol | Primarily HTTP | Protocol-agnostic (HTTP, SMTP, etc.) |
While SOAP has rigid standards that enforce a strict structure, REST offers greater freedom and adaptability, making it ideal for web and mobile applications that require quick development and deployment cycles.
Other Types of APIs
Besides REST and SOAP, you might come across other API styles, such as:
GraphQL
Developed by Facebook, GraphQL allows clients to specify exactly what data they need. This reduces over-fetching and under-fetching of data but introduces more complexity and a steeper learning curve.
RPC (Remote Procedure Call)
RPC APIs focus on calling functions or procedures directly on a server. They're fast and efficient but often lack the structure and flexibility of REST or GraphQL, making them more suitable for internal services rather than public-facing APIs.
Conclusion
Understanding what a REST API is—and why it matters—is essential for any modern web developer. REST APIs provide a reliable, scalable, and standardized way to build services that communicate across systems and platforms.
In this course, you’ll learn how to design and build RESTful APIs using Symfony 6, a powerful PHP framework trusted by developers worldwide. From creating routes to managing responses and handling authentication, you’ll gain hands-on experience building production-ready web services.
Stay tuned as we dive deeper into RESTful design principles, HTTP methods, data formatting, and more in the next lessons.
