What is REST API

What is REST API: A Beginners Guide

In the world of web development, REST API is a term that frequently comes up. It’s a fundamental concept that underlies many web services, and it plays a crucial role in enabling communication between different software systems.

In this comprehensive guide, we’ll explore what REST API is, its key principles, and how it’s used to create efficient and scalable web applications.

Table of Contents #
  1. What is an API?
  2. Introduction to REST
  3. Key Principles of REST
  4. Components of a REST API
  5. HTTP Methods in REST
  6. REST API Endpoints
  7. Advantages of REST API
  8. Disadvantages of REST API
  9. REST API Examples
  10. Building RESTful Services

1. What is an API?

API stands for “Application Programming Interface.” It is a set of rules and protocols that allow one software application to interact with another.

APIs define the methods and data formats that applications can use to request and exchange information.

In essence, an API is a bridge that enables different software components to communicate and share data.

2. Introduction to REST

REST, which stands for “Representational State Transfer,” is an architectural style for designing networked applications.

It was introduced by Roy Fielding in his doctoral dissertation in 2000. REST is not a standard but rather a set of constraints (rules) for creating web services.

RESTful systems follow these rules and use HTTP methods to perform CRUD (create, read, update, delete) operations on resources. Resources are represented as URIs (Uniform Resource Identifiers), and the interactions between clients and servers are stateless.

3. Key Principles of REST

To understand REST API, it’s important to grasp its key principles:

1. Statelessness

Each client request to the server must contain all the information needed to understand and process the request. The server should not store any client state between requests. This simplifies server design and scalability.

2. Resources

Resources are the key abstractions in REST. Everything is a resource, and each resource is identified by a URI. Resources can represent data objects, services, or entities.

3. Representations

Resources can have multiple representations, such as XML, JSON, HTML, or plain text. Clients interact with these representations to access or manipulate resources.

4. Standard Methods

RESTful systems use standard HTTP methods like GET, POST, PUT, and DELETE to perform operations on resources. These methods map directly to CRUD operations.

5. Stateless Communication

Every request from a client to a server must contain all the information required to understand and process the request. Servers should not rely on any previous requests.

4. Components of a REST API

A REST API comprises several components:


Resources are the data objects that the API manages. They can be collections or individual items. For example, in a RESTful blog API, articles, comments, and users would be considered resources.


Uniform Resource Identifiers (URIs) are used to uniquely identify resources. URIs are the URLs that clients use to access resources. For instance, /articles/123 might represent an article with the ID 123.

HTTP Methods

HTTP methods define the actions clients can take on resources. Common methods include GET (retrieve data), POST (create new data), PUT (update data), and DELETE (remove data).


Representations are the formats used to present resources to clients. They can be in JSON, XML, HTML, or other formats, depending on the API’s design.


HTTP headers convey additional information about requests and responses. They can include metadata, authentication tokens, and caching instructions.

5. HTTP Methods in REST

REST APIs utilize the following HTTP methods for CRUD operations:

  • GET: Retrieve data from the server.
  • POST: Create a new resource on the server.
  • PUT: Update an existing resource on the server.
  • DELETE: Remove a resource from the server.

These methods, along with the resource’s URI, define the action clients want to perform.

6. REST API Endpoints

An API endpoint is a specific URL or URI that clients can use to access a particular resource. Each endpoint corresponds to a specific resource and an HTTP method. For example:

  • GET /articles: Retrieve a list of articles.
  • POST /articles: Create a new article.
  • PUT /articles/123: Update article 123.
  • DELETE /articles/123: Delete article 123.

Endpoints are an essential part of a RESTful API, as they provide a clear and structured way for clients to interact with resources.

7. Advantages of REST API

REST API offers several advantages:

  • Simplicity: REST follows the principles of HTTP and uses familiar methods, making it easy to understand and implement.
  • Scalability: Stateless communication makes it possible to scale servers horizontally without concerns about session management.
  • Flexibility: REST supports various data formats, allowing clients to choose the most suitable representation.
  • Independence: Clients and servers can evolve independently as long as they adhere to the same API contract.
  • Caching: REST allows for caching of resources, which can improve performance.

8. Disadvantages of REST API

While REST API has many advantages, it also has some drawbacks:

  • Limited Functionality: REST is not suitable for real-time applications or systems that require complex querying.
  • Overfetching and Underfetching: Clients might receive more or less data than they need, which can lead to inefficient data transfer.
  • Security: REST doesn’t provide built-in security mechanisms, which must be implemented separately.

9. REST API Examples

Here are a few examples of real-world REST APIs:

  • Twitter API: Allows developers to access Twitter’s features and data.
  • GitHub API: Provides programmatic access to GitHub repositories, issues, and users.
  • Google Maps API: Allows developers to integrate mapping and location-based features.
  • Stripe API: Offers payment processing capabilities for e-commerce applications.
  • OpenWeatherMap API: Provides weather data for various locations worldwide.

10. Building RESTful Services

To build a RESTful API, you need to design your resources, define your endpoints, and implement the necessary HTTP methods. You can use a web framework like Express.js for Node.js to simplify this process.

Learn: How to build RESTful API in Node.js with Express?


REST API is a fundamental concept in web development that enables communication between different software systems.

By adhering to REST’s principles and using HTTP methods, you can design efficient and scalable web services.

Understanding the key components, HTTP methods, and design principles of REST API is essential for building modern web applications and enabling integration with external systems.