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The process in which RESTful APIs transmit data between clients and applications involves the client request and the server response.

What Is REST?

Representational State Transfer, or REST, is the architectural style of the web, which allows communicating standards between client and server. A client requests a resource, and a server will respond with the representation of that resource that can be easily interpreted.

What Is a REST API?

A REST API is a type of API that responds to a client’s request in a standardized representation, which is easy to interpret because of the uniform interface of component constraints. The response format for REST comes in HTTP, which can be JSON (JavaScript Object Notation), HTML, XLT, Python, PHP or plain text. Most developers use JSON format because it is universal and supports any language for humans and machines to interpret.

In a REST API, sometimes called RESTful API, a request must come through HTTP to a stateless protocol that does not store clients’ information during the get request session. Each request is usually disparate and unrelated.

How Does a RESTful API Work?

The process in which RESTful APIs transmit data between clients and applications involves the client request and the server response.

Client Request

The client request involves a subject, program or person using the services of the API. A typical example is when you want to share an Instagram photo on your Facebook account. In this process, you call Facebook API to help you do this.

HTTP is the protocol in the client request and there are five methods for resource requests under this protocol: POST, GET, PUT, PATCH and DELETE.

Server Response

REST transfers the resource that the client had requested from the server. However, the resource does not arrive in its actual state, but in representation standard which is a readable format and easily understandable by humans and machines. The format can be JSON, XML, YAML, CSV, HTML and plain text.

Principles of RESTful Architecture

RESTful APIs are efficient but they require certain principles to maintain high performance. These principles which set REST apart from other APIs are the foundation of its efficacy:

1. Client-Server Partition

REST API architecture requires standalone operations from the client and server. Its guidelines do not permit the client to request to know more than the URL of the resource. Also, servers cannot make requests, and neither can clients respond; only client software can make requests. The gain of this principle is that it allows the client to grow without issues affecting the server, likewise the server undergoing changes without affecting the client.

2. Uniform Interface

REST APIs adopt the standard format HTTP for application software requests and responses with the endpoints resource in the JSON format. This principle makes requests and responses between software easy to read and understand.

3. Statelessness

REST APIs require application software to request to contain all necessary information needed to process the request. Since the API does not keep record of the past request of the client, every new request is processed fast. It also means that the software can grow without developers working on memory space or overloading the server.

4. Layered System Architecture

REST API requests and responses go through various layers to ensure easy handling and distribution of functions, which makes the processing time of REST APIs faster. The segmented tiers also secure and ensure that the client nor the server do not directly communicate with themselves.

5. Cacheable

REST APIs allow caching of resources on the client or server side. It improves the speed at which the client processes while saving the resources and bandwidth of the server side.

6. Code on Demand

This principle is optional. Developers can request resources from the API in a code format, which they will execute at their end.


REST and SOAP function over HTTP and are both effective. However, they have a few differences that make developers prefer either. SOAP (Simple Object Access Protocol) has been in use before REST, but the ability to use REST without writing a single line of code has made it a faster and more preferred option.

While SOAP API is a protocol with rigid requirements, REST offers a flexible set of guidelines that are easy to implement. REST services appeal more to newer innovation like IoT mobile applications development, unlike SOAP which resonates with building compliance and meeting many enterprise needs.

Lastly, REST supports developing API with HTTP, URLs and JSON, whereas SOAP only uses XML for data transmission.

Why Use a REST API?

Many prominent companies use REST APIs for their operations on the web and cloud because they are easy to use and fast to transmit requests compared to SOAP APIs.

They are also flexible as they are not restricted to a specific type of request and can send a response in different formats. With REST APIs, developers can expand their web applications and resources without bothering if they can handle the workload that comes with it. You can always integrate REST APIs into existing technologies without compatibility issues.

The stateless architecture of REST APIs means that users’ credentials will not be in the database, which is better for security.

How to Use a REST API

REST has publicly displayed documentation that provides instructions on how to carry out integration into your software. They also come with API keys that uniquely identify you for security purposes. It is crucial to keep this key private as it will cause damages if it falls into the wrong hands. In addition, the recommendation is to test the API reliability, functionality, performance and security before integrating it into your model.

RESTful APIs are highly in use because of the ease of accessibility they offer users. Some examples of RESTful APIs include:

Instagram Basic Display API

Instagram API allows users to access other users’ information like profiles, photos and videos. Developers can also integrate this API into projects that offer related services.

Twitter API

This API is mainly for data analysis. You can also use it to generate a significant number of user data for research or products. Tweets about a specific topic can be downloaded and analyzed to understand the market requirement for a pre-launched service.

Spotify API

This API is responsible for the availability of artists’ information, songs, playlists and albums. With Spotify API, it is easy for users to add music to a playlist and shuffle them.

YouTube Data API

This API allows users to perform several YouTube operations on their websites through integration. With YouTube data API, users can search for videos, retrieve a standard feed and see related content. The API can also be integral in developing a web application that users can use to upload video content to youtube.

Challenges of REST API

Despite its flexibility, scalability and ability to handle many requests, REST faces a few challenges. Here are some of the challenges you might see with RESTful APIs:

1. Security

Since REST APIs are easy to integrate and access, they lack strict authentication measures to validate the users that send a request and the kind of date they send. This vulnerability can give attackers room to initiate various deadly attacks like denial of service, SQL injection, brute force, etc.

2. Unnecessary Data

Sometimes, REST can respond to a request with a large amount of data including some which might be unnecessary. Some of this data meant to be confidential can end up falling into the wrong hands.

3. Limited API Testing Tools

Tools available to run tests on RESTful APIs are scarce, so you might be left with the choice to go with a tool that gives less satisfaction. Moreover, the testing process is a thing to consider, as it will require you to set up the testing cycle manually, which can be daunting.

Using Test Studio to Test Your APIs

Using simple-to-create and maintain API tests, Test Studio enables teams to increase their functional testing efforts regardless of testing seniority or expertise.

With Test Studio, you can:

  • Test APIs automatically on desktop and web without writing any code
  • Check the dependability and integrity of your web services without putting in extra work
  • Integrate Your RESTful API tests into any deployment environment

Want to see Test Studio in action or check whether it fits your test automation needs? Request a quick demo here.

Verify the Integrity of your web services with API testing – Telerik Test Studio screencap

About the Author

John Iwuozor

John Iwuozor is a freelance writer for cybersecurity and B2B SaaS brands. He has written for a host of top brands, the likes of ForbesAdvisor, Technologyadvice and Tripwire, among others. Hes an avid chess player and loves exploring new domains.


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