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Understanding What Is a REST API Explained

by Marcin Wieclaw
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what is a rest api

A REST API, or Representational State Transfer API, is a software architecture that provides guidelines for managing communication on complex networks like the internet. It allows for high-performing and reliable communication at scale and brings visibility and cross-platform portability to API systems. REST APIs follow the principles of a uniform interface, statelessness, layered system, cacheability, and code on demand. These principles ensure that the server transfers information in a standard format, clients can interact independently of previous requests, and communications can occur between authorized intermediaries. Additionally, RESTful web services support caching and can extend client functionality by transferring software code.

What is a REST API and how does it work?

A REST API, or Representational State Transfer API, is a specific type of API that follows the principles of REST. It enables web services to communicate with each other and facilitates client-server interaction. When a client makes a request for a resource through a REST API, the server transfers the current state of the resource in a standardized representation, such as JSON or XML.

REST APIs work by handling requests and returning relevant information to the client. This allows clients to retrieve, modify, and delete items on the server and even add new items through the API. The API acts as an intermediary between the client and the server, translating the client’s requests into actions on the server and vice versa.

REST APIs are based on several key principles:

  • Statelessness: Each client request is independent of previous requests, and the server does not retain any information about the client’s state. This allows the server to fulfill each request consistently, regardless of the client’s previous interactions.
  • Layered System: REST APIs can support intermediaries, such as proxy servers or firewalls, allowing for scalability and enhanced network performance.
  • Cacheability: Responses from REST APIs can be cached, which improves performance and reduces the load on the server, especially for frequently accessed resources.
  • Code on Demand: REST APIs can extend client functionality by transferring executable code, such as JavaScript, which clients can execute on their end to enhance the user experience.

Overall, REST APIs provide a flexible and scalable way for web services to interact with each other. The principles they follow ensure that requests and responses are independent, can pass through intermediaries, support caching for improved performance, and can even extend client functionality through the transfer of executable code.

The Principles of a REST API

REST APIs adhere to a set of principles that govern their design and functionality. These principles ensure the efficient and effective communication between clients and servers. The key principles of a REST API include:

  1. Uniform Interface: REST APIs provide a uniform interface that standardizes the way information is transferred. Clients interact with resources using a uniform resource identifier (URI), allowing for a consistent method of accessing and manipulating resources.
  2. Resource Representation: REST APIs use self-descriptive messages to represent resources. Each resource has a specific format or representation, which includes metadata about the resource, information on how to process the representation, and hyperlinks to related resources.
  3. Statelessness: REST APIs follow a stateless approach, meaning that each client request is independent and self-contained. The server does not keep track of the client’s state between requests, allowing for greater scalability and ease of implementation.
  4. Layered System: REST APIs support intermediaries between the client and server, enabling scalability, security, and performance optimizations. Intermediaries can include load balancers, proxies, or gateways that enhance the overall system architecture.
  5. Cacheability: REST APIs support caching, meaning that responses can be stored and reused to improve performance and reduce network traffic. Caching plays a crucial role in optimizing the overall efficiency of API interactions.
  6. Code on Demand: REST APIs have the ability to extend or customize client functionality by transferring software code to the client. This allows for dynamic updates and the addition of new functionality without requiring modifications to the client itself.

“REST APIs provide a uniform interface, self-descriptive messages, stateless communication, a layered system, cacheability, and code on demand.”

By adhering to these principles, REST APIs deliver a scalable, efficient, and flexible approach to communication and resource management.


When it comes to building applications over HTTP, REST APIs and SOAP APIs are two commonly compared methods. While both serve the purpose of facilitating communication, they differ in several key aspects.

REST, or Representational State Transfer, is a set of guidelines rather than a protocol like SOAP. REST APIs leverage various methods, including HTTP, URLs, and JSON, to enable communication between systems. SOAP, on the other hand, primarily uses XML for its protocol.

One significant advantage of REST APIs is their simplicity. Compared to SOAP APIs, REST APIs require less code and offer greater flexibility in API design. The guidelines provided by REST allow developers to adopt a simpler approach, making it easier to understand and implement.

Efficiency is another area where REST APIs shine. With its lightweight architecture and support for JSON, REST APIs provide a more efficient alternative to SOAP. JSON allows for quicker parsing and interpretation, making data transfer more streamlined.

REST APIs have become the standard for building web applications, with many popular companies such as Facebook, YouTube, Twitter, and Google opting for REST over SOAP. The simplicity, efficiency, and flexibility of REST APIs make them a preferred choice for developers in the modern web development landscape.

Why Use REST APIs?

REST APIs play a pivotal role in the development of web applications, offering a range of benefits that make them indispensable in today’s digital landscape. These APIs exhibit unparalleled flexibility, scalability, and efficiency, making them the go-to choice for developers worldwide.

  • Flexibility: REST APIs excel at handling diverse types of requests and effortlessly transmitting data in different formats. This versatility empowers developers to create dynamic and interactive web apps that cater to a wide range of user needs.
  • Scalability: Web applications evolve over time, often requiring the addition of new resources and features. REST APIs seamlessly accommodate these scaling demands, ensuring that the application can adapt without compromising performance or functionality.
  • Efficiency: REST APIs provide an efficient and standardized system for viewing, modifying, and transferring content online. By adhering to uniform interface principles, REST APIs enable seamless communication between various software applications, regardless of their size or capabilities.

“REST APIs are the backbone of major web and cloud companies, including Facebook, YouTube, Twitter, and Google. Their reliance on REST APIs is a testament to the efficiency and effectiveness of this powerful technology.”

Whether it’s handling user authentication, retrieving data from a database, or integrating third-party services, REST APIs offer unparalleled value in modern web development. By leveraging their flexibility, scalability, and efficiency, developers can create robust and high-performing web applications that meet the ever-evolving demands of users.

web apps

Take a look at the following table for a quick comparison:

Flexibility Relatively simpler and more flexible
Efficiency Efficient and requires less code
Data Format Supports various formats, including JSON
Protocol Protocol-based (SOAP)

How to Send Requests to a REST API

Sending requests to a REST API involves several key components: the endpoint, method, headers, and data. Let’s break down each element to understand their significance in interacting with a REST API.


The endpoint is the specific URL where the REST API is located. It serves as the entry point for accessing the desired resources or functionalities provided by the API. When constructing requests, developers need to specify the correct endpoint to ensure successful communication.


The method refers to the type of HTTP request being made to the API. There are several commonly used methods:

  • GET: Retrieves a resource or a collection of resources from the API.
  • POST: Creates a new resource on the server.
  • PUT: Updates an existing resource with new data.
  • PATCH: Partially updates an existing resource.
  • DELETE: Removes a resource from the server.

Choosing the appropriate method is crucial as it determines the action to be performed on the specified resource.


Headers provide additional information about the request or response. They contain metadata that helps the client and server understand the content and format being communicated. One commonly used header is Content-Type, which specifies the format of the data being sent or received.


Data, often formatted as JSON (JavaScript Object Notation), can be sent along with the request. This data may include parameters, filters, or the payload needed to create or update a resource. JSON provides a lightweight and readable format for representing structured data.

Developers can use various tools and libraries to send requests to a REST API, and one popular choice is cURL. cURL is a command line utility that allows developers to interact with APIs directly from the command line interface. It supports different types of requests, headers, and data formats, making it a versatile tool for testing and debugging API interactions.

To summarize, sending requests to a REST API requires specifying the endpoint, method, headers, and data. These elements allow developers to communicate with the API and perform various actions such as retrieving, creating, updating, and deleting resources.

Understanding JSON in REST APIs

JSON, or JavaScript Object Notation, is a widely used format within REST APIs for the exchange of data. It serves as a lightweight and readable format that simplifies the transfer of information between the server and client. In JSON, data is structured similarly to a JavaScript object, with properties and values enclosed in double quotation marks.

REST APIs often return responses in JSON format, making it easy for clients to parse and interpret the data. This compatibility allows developers to work with JSON across a variety of programming languages, facilitating seamless integration and interoperability.

By utilizing JSON in REST APIs, the integrity and structure of the data are maintained throughout the communication process. This consistency ensures that the data remains accurate and reliable, regardless of the underlying technologies or programming languages used in the implementation of the API.

In conclusion, JSON plays a crucial role in facilitating efficient and standardized data exchange within REST APIs. Its simplicity, readability, and compatibility make it an ideal choice for transmitting data between the server and client in a wide range of applications.


What is a REST API?

A REST API, or Representational State Transfer API, is a software architecture that provides guidelines for managing communication on complex networks like the internet.

What are the principles of a REST API?

REST APIs follow the principles of a uniform interface, statelessness, layered system, cacheability, and code on demand.

How do REST APIs work?

When a client requests a resource through a REST API, the server transfers the current state of the resource in a standardized representation.

What is the difference between a REST API and a SOAP API?

The main difference is that REST is a set of guidelines, while SOAP is a protocol. REST APIs are considered simpler and more efficient than SOAP APIs.

Why use REST APIs?

REST APIs are widely used in web applications for their flexibility and scalability. They can handle various types of requests and send data in different formats.

How do I send requests to a REST API?

Sending requests to a REST API involves specifying the endpoint, method, headers, and data. cURL is a commonly used tool for sending requests to a REST API.

What is JSON in REST APIs?

JSON, or JavaScript Object Notation, is a common format used in REST APIs for sending and receiving data.

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