What Is A Rest API?


What Is A Rest API?

REST is a set of principles for software to interact over the internet to simplify and scale integrations. A REST API (sometimes known as a “RESTful” API) is a form of API (Application Programming Interface) that adheres to certain rules. 

The ability to share data across various systems in a standard manner is essential in this technology-dominated world. As a result, software programs employ application programming interfaces, commonly known as APIs, to communicate with one another. APIs allow two apps to exchange data in a standardized manner.   

Any third-party integration, be it a payment gateway or a registration integration, can be easily achieved using the platform’s REST APIs. Hence, having information about REST APIs is a mandatory prerequisite to having any sort of integrations done in your software.        

What Is Rest API? 

You need to be aware of a few fundamental terms before we discuss REST APIs.


The entity consuming the API is termed the client. The client will make an API call that will return a set of data in response to this API call.  

For instance, your web browser is a client; it communicates with APIs on many websites to obtain page content displayed to you. Another example is an e-commerce site that makes use of a payment gateway. In this case, the e-commerce site is the client that communicates with the payment gateway API to invoke a response. 


The information returned to the client from the API is referred to as a resource. For example, talking about calling a Facebook API to integrate social media authentication, the user’s name, age, or any other valid information given by the Facebook API is termed as a resource. Each resource, i.e. a piece of information, is identified by a unique name.    


The server works with the application that responds to the client’s request. It’s important to note that the client doesn’t have direct access to the application’s database. Instead, the server has an API that communicates with the application and gives a response to the client.

Principles of REST API 

REST APIs respond to queries for resources by delivering all necessary information about the resource in a way that clients can understand (this format is determined by the API receiving requests). Clients may alter existing objects on the server through a REST API and even create new ones.

Below are the principles on which the REST API is based. We look at:

  • Client and Server Architecture
  • Stateless
  • Cacheable
  • System with Layers
  • Consistent Interface
  • On-demand Coding

Client And Server Architecture

REST is a client-server architecture where the server and client can operate independently as long as the interface remains consistent when processing requests and responses. The server exposes the REST API and the client uses it.

The server saves the data and makes it available to the user, whereas the client takes the data and shows it to the user or utilizes it to make additional requests for more data.


REST is supposed to be stateless, which means that whenever a client and server connect, the information needed to complete the request is always included. The term “stateless” also refers to the absence of a session state, which is kept on the client’s side. If authentication is required, the client must authenticate themselves each time a request is made.   


REST is also cacheable, implying that the client, server, and any other linked intermediate component can all cache resources to increase efficiency.

System With Layers

A layered system in a REST architecture is made up of several levels, each of which has a specific purpose of accomplishing. While each layer has its own set of duties, they must also communicate with one another, resulting in a hierarchy within the REST API architecture.

Consistent Interface

Within a REST API architecture, a unified interface is created to allow the client to communicate with the server in a single language. This allows the application to grow independently of the API, with no services, models, or other intertwined functions.

On-demand Coding

Unlike the other REST guiding principles, code on demand is a choice in a REST architecture rather than a requirement. Code on demand enables the transmission of code and applets over the API for usage within the application. 

In its most basic form, code on demand allows clients to be more flexible because the server is the one who decides how things will be done in the end.

A Typical Rest Api Response In JSON Format


What Does REST Stand For In An API?

REST stands for Representational State Transfer. This implies that when a client uses a REST API to request a Resource, the server Transfers the resource’s current State back in a standardized format. 

How To Use A REST API?

Below are a few steps that you can follow in order to use a REST API:

Look Out For The Documentation

Programmers will publish documentation for online apps having publicly accessible APIs in their websites’ “developers” section. In addition, instructions on accessing and utilising the API with your own applications may be found there.  

The documentation will almost certainly state whether or not the API was created using REST principles. 

Select The Language

Public APIs support various languages. Select the coding language of your application, and check the instructions on calling the API. Most of the time, the documentation will also provide a piece of code to invoke the API.

Get Your API Key 

To utilise many APIs, you’ll need an API key. An API key is a one-of-a-kind string of characters provided by an API provider to a developer to grant access to their API. Client requests frequently include API keys that can identify the client to the server. Maintain the secrecy of your API key(s). If your key comes into the wrong hands, it might be used to carry out some nefarious acts in your name.

Select A Testing Tool 

Use a tool that can arrange HTTP requests, such as Postman, to test a public API. Experiment with various HTTP methods and URLs to see what happens.


A RESTful API is a sort of application programming interface. REST services are APIs. However, not all APIs are REST services. In simpler terms, REST API is a subset of API.

The word “API” is fairly wide. In general, it refers to how one piece of code communicates with another. For example, the way we receive information from an online service is generally referred to as API in web development.  

REST is a collection of norms, standards, and regulations for creating a web API. Because there are so many options, having an agreed-upon strategy for constructing an API saves time when deciding how to develop one and when learning how to use one.

StructureClient and server structure communicationApplication to application communication
ProtocolUses a fixed HTTP protocolThe protocol varies from application to application
ScalabilityBetter structure and scalabilityThe scalability is a point of concern for APIs
DesignThe design is complex, with a layered architecture, since REST APIs communicate with multiple applicationsThe design is lightweight

Why Use REST API?  

In 2000, computer scientist Roy Fielding invented the REST framework, which now influences how we view, change, and transmit material online. Many of the most prominent web and cloud organizations, including Facebook, YouTube, Twitter, and Google use REST APIs.

But what is the point of REST? Basically, it’s a fantastic technology for developing web applications. The following are the key advantages of using this style of API:

  • REST APIs are extremely adaptable. They may respond to a wide range of queries and provide data in a variety of forms. 
  • Scalability is a feature of REST APIs. They communicate between any two pieces of software, no matter how big or powerful they are. A web application’s REST API will be able to accommodate an increasing number and diversity of queries as it expands and adds more resources. 
  • REST APIs make use of current web technologies, making them simple to create and utilize. To use a REST API, all you have to do is supply the resource’s URL.

How To Test REST API?

Advanced Rest Client, Postman-Rest Client, and Curl in Linux are some REST API testing tools that developers may use to see if a REST API is completely ready to use. Follow these steps.

  1. In the tool’s textbox, type in the API’s URL.
  2. Choose an HTTP method for this API (GET, POST, PATCH, etc.).
  3. In the Headers textbox, type any headers that are necessary.
  4. Use a key-value pair to pass the API’s request body.
  5. Select the appropriate content type (such as application or JSON).
  6. Send your message.

After hitting Send, the REST API will respond with various replies, indicating whether the API testing was successful or unsuccessful. It’s crucial to keep track of the response code, message, and body. 


REST APIs are becoming increasingly popular for mobile apps, social networking sites, and other applications. In addition, a large number of businesses use REST APIs to generate revenue and grow their services. REST API employment will continue to be one of the most cost-saving methods to allow the next generation of business apps.

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