REST API - Definition, Function and Development

A REST API enables companies to exchange data between different applications and platforms in a standardized way. However, the development and implementation of a REST API must follow certain rules to ensure that it works efficiently. We explain what exactly a REST API is, how it differs from related technologies and how you can integrate the API into your existing processes.

What is a REST API?

rest api definition

A REST API is a technology that makes it possible to exchange information and services between different software applications in a standardized and user-friendly way. As an interface, the REST API enables communication between the endpoints of different servers as well as the development and integration of application software.

This is based on a special architectural standard for an API (Application Programming Interface), which is based on the REST (Representational State Transfer) principles. With a REST API, resources are retrieved, created, updated or deleted via the HTTP protocol.

The REST principles are

  • Client-Server
  • Statelessness
  • Caching
  • Uniform interface
  • Multilayer systems
  • Code on Demand (Optional)

How does a REST API work?

A REST API enables communication and data exchange between different software applications via the HTTP protocol. When an application requires data from another application, it sends an HTTP request to the API. This request contains information about what action is to be performed (e.g. retrieve or send data) and what data is required. The API receives this request, processes it and sends back an HTTP response. This response contains the requested data in the desired format (e.g. JSON or XML).

The REST API works on the principle of resources, where each resource is identifiable via a unique URL (Uniform Resource Locator). In this way, interaction between applications is standardized and simplified.

Example weather app

A common example of how a REST API works is retrieving weather information. If you have a weather app on your smartphone and want to retrieve the current weather for your city, the app interacts with a weather API that provides the required weather data. In this example, the REST API serves as an intermediary between the weather app and the external weather data. It enables simple and standardized data exchange so that the app always provides up-to-date weather information. 

  1. Send request
    In the app, you enter your location or the app automatically uses your current location. It then creates an HTTP request to the weather API. This request contains the necessary information such as the type of request (e.g. "GET" for data retrieval) and the desired location (e.g. "Berlin").
  2. Processing through the API
    The Weather API receives the request and reads the desired location. In this case, it can access its database or external sources to retrieve the current weather data for Berlin.
  3. Return answer
    The API creates an HTTP response with the current weather data, such as temperature, humidity, and weather conditions. This data is often structured in JSON or XML format. The API sends this response back to the weather app.
  4. Display of the data in the app
    The weather app receives the response from the API and extracts the weather information. Then it displays this information on your smartphone screen so that you can see the current weather in Berlin.

Principles of a REST API

To create a functioning REST API, developers must follow various design principles and design guidelines. These help to design clear, scalable and easy-to-understand interfaces for data exchange between different software applications.

The REST principles help to design clear, scalable and easy-to-understand interfaces between different software applications.


REST APIs require a client-server constellation that divides tasks between the program that requests information (the client) and the program that provides that information (the server). The client sends requests to the server, and the server returns the requested data or services.


The server does not store information about previous requests from a client. Each request from the client must contain all the necessary information for the server to understand. This facilitates scalability and developer friendliness.


Caching allows the client to temporarily store responses from the server for later reuse. If the data has not changed, the client reuses the cached response, which increases efficiency.

Uniform interface

The uniform interface is a central principle of REST and comprises several aspects. The REST API identifies resources (data or services) via unique URLs. It can represent and change these resources in various formats (e.g. JSON or XML). In addition, each message contains sufficient information to be understood by the client or server - including information about the media type and method (e.g. GET or POST). Clients also use hyperlinks in the responses to navigate through the application - similar to how you click on links on a web page to go to different pages.

Multilayer systems

This principle allows the implementation of REST architectures in multiple layers, for example with load balancers and proxies. In this way, the API is more scalable and secure. In practice, an e-commerce company, for example, uses a load balancer to distribute traffic across different servers. In this way, it maintains website performance even when traffic is high. In addition, the company uses proxies to block unwanted requests and protect the API from threats. This way, the online store runs smoothly.

Code on Demand (optional)

This principle is optional and allows the server to send executable code to the client when required. In the example of developing an e-commerce website, the server transmits dynamically generated code with JavaScript to the client when the user makes a search query, instead of sending pre-defined HTML pages. This enables the client to immediately filter the product selection based on the search criteria without having to make a new request to the server. This improves website performance and user experience. However, this technique is less common due to its complexity and potential security risks. In most cases, companies use simpler approaches such as AJAX to achieve dynamic updates on the client side.

Delimitation of the REST API

rest api vs.

In addition to the REST API, which was developed in 2000 by a group of developers led by scientists Roy Fielding there are other architectural approaches to interfaces. In the following, we explain the features and differences between the various interfaces.


An API (Application Programming Interface) is an interface that enables applications to communicate with each other. A REST API is a special type of API that uses the HTTP protocol and works according to clear principles. While APIs are more general and use different protocols, a REST API follows a defined set of rules to exchange data over the internet. 


A REST API and a Web API are basically the same thing, as REST is an approach to designing Web APIs. The main difference lies in the design philosophy. REST is based on certain principles, such as the use of HTTP methods (GET, POST, PUT, DELETE) and the use of URLs to identify existing resources. REST is easy to understand and often uses JSON or XML for data.

A Web Application Programming Interface (WEB API) is a more general term and uses various architecturesincluding REST. Other approaches such as SOAP (Simple Object Access Protocol) or GraphQL are also types of Web APIs. This means that REST APIs follow a uniform pattern, while Web APIs use different design styles. In practice, however, most Web APIs today use the REST approach because of its simplicity and widespread adoption.


A REST API and HTTP (Hypertext Transfer Protocol) are closely related, but there is a key difference. HTTP is a protocol that enables communication between a web browser and a web server. It regulates how information is transferred on the Internet, for example when calling up websites or sending e-mails. It is fundamental to the functioning of the World Wide Web.

REST API, on the other hand, is a concept or pattern for building interfaces that allow different software applications to communicate with each other. REST often uses the HTTP protocol as the basis for communication, but it is broader and refers to the way requests and responses are structured and how resources are identified via URLs.


REST API and SOAP are two different technologies that make it possible to exchange data and functions between software applications to exchange data. REST is lightweight and often uses the HTTP protocol. It uses clear and readable URLs to address resources and often works with JSON or XML as the data format. REST is easy to understand and well suited for open web APIs.

It uses XML as a message format and works via various protocols such as HTTP and SMTP. SOAP, on the other hand, is a protocol-based communication format. It is usually more complex and requires more overhead, but offers advanced features such as transaction support and increased security. The choice between the two technologies depends on the specific requirements of a project.

Konfuzio - A powerful REST API

With Konfuzio's API and servers, companies build their own data and application service. To provide customers with the highest level of efficiency and resilience in doing so, Konfuzio combines artificial intelligence,, machine learning as well as Deep Learning,. In practice, this enables companies to develop an easily scalable, extremely flexible and powerful REST API that meets even the highest requirements.

Konfuzio's REST API is powerful and has a large number of flexible interfaces to enable versatile communication between endpoints and servers. In this way, processes can be sustainably optimized across all software.

Christopher Klee Avatar

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