Why do we call API as REST API?

why do we call api as rest api: 93% use this style

Understanding why do we call api as rest api helps developers select efficient tools for building modern web services. Ignoring these architectural standards leads to poor scalability and creates unnecessary complexity for teams managing public mobile applications. Review these core principles to improve project performance and streamline your development workflow.

What Exactly is an API?

An API, or Application Programming Interface, is a general term for any software intermediary that allows two separate applications to talk to each other. It defines the rules and protocols for how one piece of software can request data or a service from another. Think of it as a menu in a restaurant - the menu lists the dishes you can order, and the kitchen (the server) prepares and delivers them.

Why We Call Some APIs "REST APIs"

The term REST API refers to an API that adheres to the representational state transfer explained through its core principles. This style was defined by computer scientist Roy Fielding in his 2000 doctoral dissertation. The name REST describes how data is handled: a representation of the resources current state is transferred between the server and the client. When you request a users profile, the server doesnt send you its raw database record; it sends a representation of that data, usually in a lightweight format like JSON or XML.

The Six Guiding Principles of a REST API

For an API to be considered truly RESTful (or REST), it must follow six key architectural constraints. These principles are what give REST APIs their well-known benefits of scalability, simplicity, and performance.

1. Uniform Interface

This principle standardizes the way clients interact with the server. It relies on standard HTTP methods to define actions: GET (retrieve data), POST (create new data), PUT/PATCH (update existing data), and DELETE (remove data). This creates a consistent, predictable pattern for all resources. Its the reason you can interact with virtually any REST API using the same simple set of commands.

2. Statelessness

This is a core characteristic. In a stateless API, the server does not remember or store any information about the clients session between requests. Every request from the client to the server must contain all the information necessary to understand and process it. This constraint makes the server simpler to design and easier to scale, as it doesnt have to manage session state.

3. Client-Server Architecture

This is a fundamental separation of concerns. The client (the user interface or front-end) is responsible for the user experience, while the server (the back-end) is responsible for data storage and business logic. This separation allows the client and server to evolve independently; you can change the front-end technology without affecting the back-end, and vice versa.

4. Cacheability

REST APIs are designed to work well with the caching infrastructure of the web. Responses from the server must explicitly declare themselves as cacheable or non-cacheable. If a response is cacheable, the client can reuse the same response for an equivalent request in the future, dramatically improving performance and reducing server load for frequently accessed data.

5. Layered System

A client connecting to a REST API cannot usually tell if it is connected directly to the end server or to an intermediary, such as a load balancer, a security layer, or a caching server. These layers can be added to improve scalability and security without the client needing to know anything about them. This architecture provides flexibility and helps manage complexity in large systems.

6. Code on Demand (Optional)

This is the only optional constraint. It allows a server to temporarily extend the functionality of a client by sending executable code, such as a Java applet or a JavaScript script. This is not commonly used in modern REST APIs.

REST API vs. A General API: What's the Difference?

The key difference between api and rest api is that API is a broad concept, while REST API is a specific implementation of that concept. All REST APIs are APIs, but not all APIs are REST APIs. A general API can follow any design style or protocol (like SOAP, gRPC, or GraphQL). A rest api architectural style is a specific architectural style that imposes the constraints above to leverage the existing infrastructure of the web (HTTP) for better performance, scalability, and simplicity.

Why REST APIs Have Become the Industry Standard

RESTs dominance isnt by accident. Its simplicity and alignment with the webs architecture have made it the go-to choice for modern development. It uses the familiar HTTP protocol, making it instantly understandable to any web developer.

The use of lightweight data formats like JSON reduces overhead and is easy for both humans and machines to read. This combination of factors makes why do we call api as rest api a common question among developers. This combination of factors makes REST APIs incredibly scalable and flexible, which is why they power the vast majority of public web services and mobile apps today. 93% of organizations use REST APIs as their dominant architecture, and 89% of organizations use REST as their primary API format.^[2]

A Real-World Look: From Monolith to Modern Microservices

API Architectural Styles at a Glance

REST API

1. Stateless. Each request is independent and contains all necessary info.
2. Typically JSON (also XML, HTML, plain text). Lightweight and human-readable.
3. Web services, mobile apps, public APIs, and microservices where simplicity and scalability are key.
4. Architectural style (not a protocol). Uses HTTP.

SOAP API

1. Can be stateful or stateless. More complex to manage.
2. Only XML. Verbose and requires more bandwidth.
3. Enterprise-level applications requiring high security, ACID compliance, and formal contracts (e.g., banking).
4. A strict, official protocol with built-in rules.

FinCorp's Journey from SOAP to REST

FinCorp, a legacy financial services firm, was struggling with its internal customer management system. Their SOAP API was slow, with an average response time of over 800 milliseconds. Integrating new mobile apps required complex XML parsing and strict adherence to WSDL contracts, slowing down development to a crawl.

The development team decided to modernize and migrated to a REST API architecture. The first version was a direct one-to-one translation, which failed to solve the underlying performance issues.

The breakthrough came when they redesigned resources around business concepts and leveraged HTTP caching. By identifying that customer profile data changed infrequently, they implemented HTTP caching headers, allowing mobile clients to reuse responses for up to an hour.

The result was transformative. Response times for cached requests dropped to under 100 milliseconds, representing a significant improvement.^[3] Development velocity increased as front-end teams could now work with simple, human-readable JSON without needing complex SOAP toolkits. FinCorp successfully scaled to handle a 200% increase in mobile traffic during peak hours without any server upgrades.