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API Testing Tools

API testing is a type of software testing that involves testing application programming interfaces (APIs) directly and as part of integration testing to determine if they meet expectations for functionality, reliability, performance, and security. Since APIs lack a GUI, API testing is performed at the message layer. API testing is now considered critical for automating testing because APIs now serve as the primary interface to application logic and because GUI tests are difficult to maintain with the short release cycles and frequent changes commonly used with Agile software development and DevOps.

This post will provide a summary of some API testing tools covering both open-source and commercial solutions that testing teams can select to suit their needs.

1. Postman


Postman is a good choice for API testing for those who don’t want to deal with coding in an integrated development environment using the same language as the developers.

  • Easy-to-use REST client
  • Rich interface which makes it easy to use
  • Can be used for both automated and exploratory testing
  • Can be run on Mac, Windows, Linux & Chrome Apps
  • Has a bunch of integrations like support for Swagger & RAML formats
  • Has Run, Test, Document and Monitoring Features
  • Doesn’t require learning a new language
  • Enable users to easily share the knowledge with the team as they can package up all the requests and expected responses, then send to their colleagues.

Plans and pricing

Free! For Individuals & Small Teams

Postman Pro: $8 Per user/month billed annually (Teams up to 50 users)

Postman Enterprise: $18 Per user/month billed annually (Teams of any size)

2. Insomnia


  • Easy for switch between environments with separated variables
  • Ability to reference response values of other requests
  • Generate code snippets to almost any language your want
  • Unlimited installations with Free plan
  • Available for Mac/Windows/Linux App and Google Chrome extension

Plans and pricing
Free: forever – Mac/Windows/Linux App – Unlimited installations – Free updates forever

Plus: $5 / month or $50 / year | All Free features + E2EE data sync & Unlimited devices

3. SoapUI


SoapUI is an open-source web service testing application for service-oriented architectures (SOA) and representational state transfers (REST). Its functionality covers web service inspection, invoking, development, simulation and mocking, functional testing, load and compliance testing

Plans and pricing

Free package: Using the free package of SOAPUI, users can get the full source code and build their preferred features

Fixed License
– SoapUI Pro 1 Year License: $ 659
– SoapUI Pro 2 Year License: $ 1319
– SoapUI Pro 3 Year License: $ 1979

Floating License
– SoapUI Pro 1 Year License: # 4609

4. Katalon


  • Simple Deployment: All frameworks, ALM integrations, and plugins are included in a single package for Windows, macOS, and Linux.
  • Easy to Use: Friendly UI for users to quickly create, execute, and maintain tests. Minimum programming skill required. Sample projects to start in no time.
  • Full Feature Set: All functionalities ready for Web, API, and mobile (iOS and Android) automation with team collaboration and test management.
  • Active Community: 350K+ automation testers with YouTube channels, GitHub repositories, and Udemy courses dedicated for Katalon Studio.
  • Support both SOAP and Rest
  • All-in-one shop for API, WebUI and Mobile testing and the combined capabilities among those.
  • Support data-driven approach.
  • Can be used for automated and exploratory testing
  • Support CI/CD integration.
  • Support AssertJ, one of the most potent assertion library, to create fluent assertion with BDD style
  • Suitable for both non-techies and pros via Manual and Groovy Scripting modes

Price and Plans

Price: Free

Support Service Pricing (different plans starting from $2.500 per year)

5. Tricentis Tosca


Tricentis Tosca allows testers to rapidly create API tests from an intuitive business-readable interface and then integrate them into end-to-end test scenarios. Even if you’re new to API testing, it’s simple to get started in minutes.

  • Supports many array of protocols: HTTP(s) JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ,NET TCP
  • Integrates into the Agile and DevOps Cycle
  • Maximize reuse and maintainability with model-based test automation
  • API tests can be used across mobile, cross-browser, packaged apps, etc…
  • Achieve sustainable automation with new technology
  • Reduce the time of regression testing

Pricing and plans

Contact Sales

6. Apache JMeter


The Apache JMeter™ application is open source software, a 100% pure Java application designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.

Apache JMeter may be used to test performance both on static and dynamic resources, Web dynamic applications.
It can be used to simulate a heavy load on a server, group of servers, network or object to test its strength or to analyze overall performance under different load types.

Plans and pricing Free

7. Rest-Assured


Testing and validating REST services in Java is harder than in dynamic languages such as Ruby and Groovy. REST Assured brings the simplicity of using these languages into the Java domain

REST-Assured is a fluent Java library you can use to test HTTP-based REST services. It’s designed with testing in mind, and it integrates with any existing Java-based automation framework.

It provides a behavior-driven development (BDD)-like domain-specific language that makes creating API testing in Java simple.

The REST-Assured API is created so that you don’t necessarily need to be an HTTP expert. 

Plans and pricing Free

Which one is your favorite?

There are many alternatives available in the market. API test tools work very well and are there are great options, depending on your team’s needs and budget. Which one is your favorite?

API Testing Tools
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