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Api.co.id – If you work in the digital or tech industry, chances are you’ve heard the term REST API before. In today’s interconnected world, applications rarely operate in isolation. Instead, they constantly communicate and exchange data with one another — and REST APIs make that possible.

REST API acts as a bridge that allows one application to interact seamlessly with another, regardless of the programming language or platform being used.

What Is a REST API? Here’s the Definition

REST stands for Representational State Transfer, while API refers to an Application Programming Interface.

In simple terms:

REST is a standardized architectural style that defines how applications can communicate and exchange data efficiently.
API is the interface or “middleman” that enables two applications to talk to each other.

A REST API uses HTTP (Hypertext Transfer Protocol) to access, send, and retrieve data securely over the internet. You can think of it as a web service that manages the interaction between a client (the requesting application) and a server (the provider of the data).

Even if two systems are built using different programming languages, the HTTP protocol used by REST APIs translates the request into something both sides can understand. This makes the communication process safe, simple, effective, and highly efficient.

Also read: What Is an API? Definition, Types, and How It Works

Core Principles of REST API

REST APIs are intentionally designed to be simple, lightweight, and easy to use. To understand how they function, you need to learn the key characteristics that define them:

1. Stateless

REST APIs are stateless, meaning the server does not store any information about previous requests from the client.
Each request must contain all the necessary data for the server to process it.

Because the server does not remember past interactions, this ensures:

Higher reliability
Simpler server design
Faster performance

2. Clear and Well-Defined Resources

In REST API, the data you interact with is referred to as resources.
Each resource is accessed via a unique URL that clearly represents what it contains.

A properly designed REST endpoint might look like:

/users
/products/123
/orders/456/items

This clarity makes it easier for both the client and server to understand what data is being requested.

3. Uses Standard HTTP Methods

REST APIs rely on standard HTTP methods to specify the action being performed. The most commonly used methods are:

GET – Retrieve data
POST – Create new data
PUT – Update existing data (replace)
PATCH – Update part of existing data
DELETE – Remove data

These universal methods create a predictable interaction pattern that developers can easily follow.

4. Cacheable Responses

Certain REST API responses can be cached to improve performance.
If the requested data rarely changes, the client can store it temporarily to avoid making repeated requests.

Benefits of caching:

Faster application performance
Reduced load on the server
Lower bandwidth usage

How Does a REST API Work?

Although REST API architecture may sound technical, the actual workflow is straightforward. It all revolves around a cycle of HTTP requests from the client and HTTP responses from the server.

Below is the simplified flow:

1. The Client Sends an HTTP Request

The client (such as a web app, mobile app, or external system) sends a request to the server. This request includes the desired action and often carries data.

Examples:

GET to retrieve data
POST to send or create new data
PUT to update data
DELETE to remove data

2. The Request Is Sent to the Correct Endpoint

Every request must include a valid endpoint URL.
The endpoint tells the server which resource the client wants to interact with.

For example:
GET /users/10 → Retrieve information about user with ID 10.

A precise URL ensures faster and more accurate responses.

3. The Server Processes the Request

Once the request is received, the server:

Checks the endpoint
Validates the method (GET/POST/etc)
Retrieves or modifies the necessary data
Performs any required logic or operations

This may involve querying the database, updating records, or validating the request.

4. The Server Sends Back a Response

After processing the request, the server returns an HTTP response containing:

The requested data (if applicable)
A status code indicating the result (e.g., 200 OK, 201 Created, 404 Not Found, 500 Error)

The response is formatted in commonly used formats such as JSON or XML, with JSON being the most popular.

5. The Client Processes the Response

The client then processes the data based on the original request.

For example:

If the request was GET, the application displays the retrieved data.
If it was POST, the client may show a success message or update the UI accordingly.

This completes one full cycle of communication.

Conclusion

After understanding what a REST API is — including its definition, key principles, and workflow — it becomes much easier to see why it’s so widely used in modern software development.

REST APIs offer simplicity, efficiency, and compatibility across different systems, making them an essential tool for developers building scalable applications and interconnected digital services.

Read the Indonesian version of this article here: Apa itu REST API? Pahami Pengertian, Prinsip-Prinsip, dan Cara Kerjanya!

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What Is a REST API? A Complete Explanation for Beginners