The 10 Best API Testing Tools on the Market
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The 10 Best API Testing Tools on the Market

Application Programming Interface Testing, or API, is a method of software testing that measures the standard of developed APIs, and whether or not they meet standards of functionality, performance, and security.

Over the last couple of years, there has been a rise in interest in API/Web services testing.

According to research conducted by Smartbear in 2017, the amount of API testers that automates over half of their tests is predicted to expand by 30%.

Using an effective method, as well as having the correct tools and solutions for API automation tests is of increasing importance; to have a successful CI/DevOps practice, API testing is vital.

The following article discusses the top API testing tools, which range from open-source and commercial solutions depending on the specific needs of testing teams.

1. SoapUI

SoapUI is a functional testing tool that addresses API testing. Because it is headless, users can test REST and SOAP APIs and Web services with ease.

Free package: the free SoapUI package allows users to gain access to the full source code and create their preferred features.

  • Rapidly create a test with Drag and drop, Point-and-click
  • Reuse of Scripts: within several steps, load tests and security scans can be reused in functional test cases

Pro package:

  • Groovy allows for efficient creation of custom code
  • Data is extracted from files, databases, and excel so consumer interactions with API can be simulated
  • Support of native CI/CD integrations


Pricing: Free – $659/year

2. Katalon Studio

Katalon Studio is a free test automation tool that is compatible with API, Web, and Mobile applications, and is quickly increasing its scope as a top tool for API/Web services testing by being the comprehensive solution developers and testers need.

Katalon Studio also supports SOAP and REST requests, as well as the range of commands and parameterization functionalities they require. Additionally, the ability to combine UI and API/Web services to function in multiple environments such as Windows, Mac OS, and Linux is a unique feature among even the best API tools.

Feature highlights:

  • Supports both SOAP and Rest
  • Can be employed for both automated and exploratory testing
  • Supports a data-centric approach
  • Covers API, WebUI, and Mobile testing as well as their respective features
  • Supports CI/CD integration and AssertJ, allowing for a fluent assertion with BDD style
  • Accessible to non-tech savvy people as well as professionals with both Manual and Groovy Scripting modes


Pricing: Free

3. Postman

Although it was developed as a plugin for Chrome, Postman is also compatible with Mac and Windows as well. Some benefits include:

  • Simple to use REST client
  • Offers automated as well as exploratory testing
  • Offers many integrations such as support for external editors
  • No requirement for learning a new language


Pricing: Free or $21 per month per user

4. Apigee

As a cross-cloud API tool, Apigee offers the wonderful benefit of allowing users to access its features using other editors. Users can test performance as well as build API using other editors such as Swagger while using Apigee.

  • Able to track API traffic, response times, as well as error rates.
  • Allows for easy creation of proxies from Open API Specification
  • Built for robust digital business, compatible for APIs with tons of data.
  • Powered by JavaScript


Pricing: $2500 per month

5. Tricentis Tosca

Compatible specifically with Agile and DevOps, Tricentis Tosca offers many benefits. It is an automated continuous testing system featuring resilient testing across many application stacks.

  • Compatible with mobile, packaged, and cross-browser apps
  • Faster time for regression testing
  • Supports HTTP(s), JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, IBM, REST, as well as other protocols
  • Features efficient model-based test automation


Pricing: Varies, contact sales

6. API Fortress

API Fortress specifically targets REST and SOAP APIs, and remains the most powerful monitoring tool for the two. Known for its simplicity, API Fortress has already successfully enticed many enterprises to make the switch.

  • Offers easy test generation with one click.
  • Compatible with the cloud and with physical hardware.
  • Amazing notification and data integration
  • Simplistic UI for beginners


Pricing: $1500 to $5000 per year

7. Assertible

Focusing on reliability, Assertible is a popular choice amongst recent developers.

  • Offers support that validates HTTP responses with turn-key assertions
  • Offers support for tests after launch, compatible with GitHub, Slack, Zapier
  • Offers support for testing through each step of an integration


Pricing: Free to $500 per month

8. JMeter

Although created for other purposes, this open source tool is popular for API testing.

  • Allows replay of results
  • Offers the option to include tests in CI pipelines
  • Compatible for both static and dynamic resources


Pricing: Open source

9. Karate DSL

A relatively new testing tool, Karate DSL focuses on creating scenarios for tests in a simple manner. Users do not need to write step definitions, as KarateDSL creates them for quick kickstarting.

  • No Java experience required
  • Creates reports similar to Java projects
  • Simple to learn for novices
  • Offers support for multi-threaded parallel execution


Pricing: Open Source

10. Rest-Assured

As its name suggests, Rest-Assured is a language that allows users to easily test REST service.

  • Offers tons of built-in functions for a quick jumpstart on coding
  • Users do not need extended HTTP knowledge
  • Compatible with Serenity automation framework
  • Allows combination of UI and REST tests in one framework


Pricing: Open Source


Of course, there is no such thing as a one-tool-fits-all. Although we have covered some of the best testing tools on the market, it’s important to realize that each situation is unique, and you may have to be flexible and try several programs before finding the best one for your product. While some prefer the easy to use commercial options, others may choose the affordable yet more complex open source programs.

Always keep benefits and drawbacks in mind as you explore each testing option. Before making a decision, carefully consider your requirements and the aspects of each solution!

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