Top 6 API testing tools for developers

Top 6 API testing tools for developers
Written by Debarghya DasDecember 1, 2021
10 min read
Software Testing
Debarghya Das

Junior Front-End Developer

This article features the six best API testing tools, but first, we will explain what an API is and the benefits of API testing.

What is an API?

APIs (Application Programming Interfaces) allow applications to interact and communicate with each other by establishing precise rules and determinations. More specifically, they are responsible for stipulating the types of requests that an application can make to another and for defining the following three aspects: how to make those requests, in what data format, and what practices the user must follow.

Because of APIs, an application associated with the web can send the solicitation (with information) to a server, and, thusly, the server will recover the ask for and decipher it. At the point when the essential activities are executed, it sends a reaction back to the application's UI with data.


What are you know about API testing?

API testing consists of software that tests how the APIs were developed. It analyzes whether the APIs correctly fulfill their purpose in order to ensure the application's functionality, reliability, security, and performance are not compromised. Moreover, API testing mainly entails testing SOAP web services or REST APIs, using JSON or XML message payloads, which are sent through HTTPS, HTTP, MQ, and JMS.

The best API testing tools

1. Apigee

Apigee is a very interesting cross-cloud API testing software powered by JavaScript that allows developers and testers to access its features via different editors.

This tool is compatible with APIs that contain large amounts of data, being great for hearty and complex computerized organizations. In addition, it can without much of a stretch distinguish issues that are compromising execution by breaking down the API traffic, reaction times, and potential mistake rates. In addition, Apigee additionally empowers the making of intermediaries from Open API Specification.

Apigee provides a free trial, which allows taking it for a test ride before making any decisions. Afterward, to continue using it, organizations and testers must choose the most suitable package. The existing packages are Evaluation, Standard, Enterprise, and Enterprise Plus.


2. SoapUI

SoapUI is a software tool 100% dedicated to API testing that enables executing tests on SOAP APIs and also on web services REST, considering that it is headless. It is often one of the preferred tools by testers since it allows them to create complex scenarios and further supports asynchronous testing. Plus, it also stands out for its great data-driven testing and easiness of use.

SoapUI offers two packages, one free and the other paid (the pro package). The free solution is fairly easy to use, and testers can reutilize scripts. In the pro package, it is additionally possible to create custom code, extract data (from databases, files, and excels), and support native CI/CD integrations.



Katalon is a popular test automation tool for APIs, as well as web applications and desktop and mobile apps. It supports SOAP and REST requests and provides multiple parameterization features and commands. Additionally, Katalon follows a data-driven approach, supports CI/CD integrations, and allows testers to execute automated and exploratory testing.

Probably the best benefit that this product has is that, regardless of the various valuable highlights it offers, it isn't exceptionally difficult to utilize, being appropriate in any event, for non-nerds.

Katalon offers a generally excellent and complete free bundle. Moreover, clients can likewise pick Studio Enterprise (76$/month), which incorporates expanded highlights and private modules. As another option, there is additionally the Runtime Engine bundle (54$/month) that further executes tests in CI/CD pipelines or through the order line interface.



Although it was built as a plugin for Google Chrome, Postman can also be used with Windows and Mac and is an excellent tool for testing API services, including monitorization, debugging, running requests, etc.

Postman does not require developers or testers to learn a new language and further supports various formats (like Swagger and RAML). In addition, it additionally gives work in instruments, work areas, and assortments. Oppositely to CURL, Postman isn't an instrument that depends on the order line; accordingly, designers and analyzers don't have to glue the text into the order line window.

Postman is a free API testing tool. For those who wish to benefit from additional features, then it costs 12$ per month for each user.



Tricentis is one of the top decisions for the people who wish to coordinate it into the Agile and DevOps Cycle. It follows model-based test robotization, which works with script maintenance, and gives a quick an ideal opportunity for regression testing.

One of the primary pros is that it supports multiple protocols, such as REST, SOAP, HTTP(s), MQ, JMS, NET TCP, IBM MQ, etc. Another great plus is that Tricentis allows end-to-end testing across mobile, cross-browser, and packaged apps.

Regarding the pricing, it may vary according to the specifications of each package.



Developers and testers generally see Assertible as one of the top API testing instruments with a high spotlight on unwavering quality, thinking of it as supports API tests at each progression that goes from continuous integration to the delivery pipeline.

Further, Assertible provides users with very useful features. It supports integration with GitHub, Zapier, and Slack. Additionally, Assertible also validates HTTP responses with turnkey assertions.

This API testing tool offers three different packages. The standard version costs 25$ per month; the startup plan is 50$ per month; the business plan is the most expensive package (and the one that offers more features), which costs 100$ per month. Moreover, there is also a free personal plan that is suitable for executing more manageable API tests and understanding how Assertible works.



While picking an API testing instrument is important to consider how every one of the various choices accessible in the market may be more appropriate for specific purposes. Sometimes developers and testing teams may even opt to use more than one tool, considering that it can be complicated to find the perfect and ideal tool. Therefore, groups ought to focus on the "must-have" highlights they look for.

Along these lines, even though all the mentioned solutions in this article hold a high-quality reputation, the best API testing tool will always be the one that better fulfills the organization's or project's needs.

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Debarghya Das
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