Rest APIs are a vital part of every digital application nowadays. It’s crucial to verify that APIs are working fine before applications are delivered to end-users. Rest APIs testing is carried out manually as well as automatically. When testing Rest APIs, we send various HTTP/S requests using GET, POST, PUT, PATCH, and DELETE methods to ensure that the functionality is working great. Rest APIs testing also includes validating response versus the defined inputs, checking the accuracy of response, and checking HTTP status codes and error codes.


Testerum is one of the latest tools in the automation testing field. This tool is free & open-source, and very convenient to use due to its user-friendly UI. It uses behavior-driven development (BDD) to illustrate test scenarios and does not require any programming skills.

Katalon Studio

Katalon Studio is another test automation tool that supports testing Rest APIs. It is a free tool built on Appium and Selenium. However, it’s not open-source and can be run on multiple OSs like Windows, macOS, and Linux. This tool has a moderate learning curve and requires basic programming skills for using it. It can be integrated into CI/CD environments using Docker. Furthermore, it generates reports and statistics about test data. In contrast to Testerum, Katalon has a big community to help with difficulties.


Rest-Assured is an open-source testing tool built on top of Java. With this tool, users don’t have to write codes from scratch since it has a bunch of baked-in functionalities. It can also be integrated with Maven and CI/CD. On top of that, Rest-Assured supports BDD Given/When/Then syntax so that users don’t need to have much expertise in HTTP to use the tool. That syntax makes code more readable and cleaner.


Postman is a scalable API testing tool that can be used for both automated and exploratory testing. This tool supports Windows, macOS, and Linux and has the ability to mock APIs. Furthermore, Postman can be integrated with the CI/CD environment, and developers use it as an API development environment. This tool does not require coding knowledge so that it can be used smoothly by both developers and testers for API testing.

Karate DSL

Karate is the only open-source tool to combine API test automation, mocks, performance testing, and even UI automation into a single, unified framework. The BDD syntax popularized by Cucumber is language-neutral and easy for even non-programmers. It includes multiple steps with Given/When/Then/And/But syntax. Therefore, users can start testing very quickly without writing step definitions.


SoapUI is a leading API testing tool designed by SmartBear. It supports data-driven testing and comes as a free as well as a pro version. The Pro version supports native CI/CD integrations and asynchronous testing. It has a very user-friendly GUI and convenient for functional testing as users can test complex scenarios without writing any background scripts. SoapUI also facilitates options for test debugging that lets users monitor the execution step by step.


This article has discovered the top testing tools which help to achieve the best Rest APIs testing performance. Not every testing tool fits your application. Using this, you should be able to select the most suitable testing tool for your demand.

Senior Software Engineer and Freelance Technical Writer. I write about any Computer Science related topic.