API Testing Tools

API testing is a complex and yet important part of software development. It can be difficult to test APIs, but it is necessary to ensure that they are working properly before releasing them into the world.

There are many tools available for API testing, which can make it even more difficult to know what tool will work best for your unique needs. This blog post will give an overview of some popular API testing tools so you have a better idea on how to choose the right one for your team.

What is API Testing?

The term API stands for Application Programming Interface. API testing is a type of software testing that verifies the correct implementation of an application programming interface (API) that allows software components to communicate with each other.

It involves the process of checking the behavior and functionality of application programming interfaces (APIs). This can be done manually but it’s much more efficient to automate this process.

List of Best API Testing Tools

#1. Katalon Studio

Katalon Studio

Best for both beginners and experts testers.

Katalon Studio is a free tool to automate tests for APIs, desktop, mobile, and web apps. It supports SOAP/REST requests and offers multiple parameterization features. Katalon is data-driven, supports CI/CD integrations, and allows testers to execute automated and exploratory tests. Moreover, it’s unique ability to integrate UI and API/Web service to work in multiple environments, such as Windows, Mac OS, and Linux, is a feature that even the most advanced API tools do not have.


  • It supports AssertJ, one of the most potent assertion libraries, to create fluent assertion with BDD style.
  • Supports a data-centric approach.
  • It can be used for both automated and exploratory testing.
  • It provides insightful test report dashboards of all testing stages for the better monitor as well as collaboration across teams.
Try Katalon Studio

#2. Postman


Best for developers to manage every stage of the API lifecycle.

Postman is a collaboration platform for API development used by thousands of companies and millions of developers across the globe. It simplifies each step of building an API and streamline collaboration so you can create better APIs—faster. Earlier it was a Chrome plugin, but now extends its solution to native versions of Windows & Mac.


  • This tool can be used for both automated and exploratory testing.
  • It enables users to run requests, test and debug, create automated tests, and mock, document, and monitor API.
  • It offers various integrations like support for Swagger & RAML formats.
  • Postman also provides Run, Test, Document, and Monitoring features.
Try PractiTest

#3. SoapUI


Best for executing end-to-end tests on REST, SOAP, & GraphQL APIs, JMS, JDBC, and other web services so you can deliver software faster than before.

SoapUI by SmartBear is an excellent functional testing tool that is headless and allows users to easily test APIs and Web Services. Because it supports asynchronous testing and allows for complex scenarios creation, it is often a preferred tool by testers. It is also known for its data-driven testing and ease of use.


  • It supports REST, SOAP, GraphQL, JMS, XML-RPC, MQTT, and other protocols and collections.
  • Users can create tests easily and quickly with Point-and-click and Drag-and-drop.
  • Reuse your functional test cases as load tests and security scans in just a few clicks.
  • Powerful data-driven testing: Load data from Excel, files, and other databases to simulate the way consumers interact with your APIs.
Try PractiTest

#4. Tricentis Tosca


Best for optimizing and accelerating end-to-end testing of your entire digital landscape.

Tricentis is a Continuous Testing platform that accelerates testing with a no-code, script-less approach for end-to-end test automation. It uses model-based automation to automate script maintenance and provide a quick time frame for regression testing. Tricentis also allows end-to-end testing on mobile, cross-browser, and packaged apps.


  • It supports HTTP(s), JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, IBM, REST, as well as other protocols.
  • Its Service Virtualization feature solves the problem of trying to test responses from systems that are difficult to access or that have not been built yet.
  • It also integrates into the Agile and DevOps Cycle.
  • Users can record their day-to-day activities that can then be converted into automated test cases.  
Try PractiTest

#5. Apigee


Best for building and scaling API programs with full API life cycle capabilities.

Apigee is a cross-cloud API testing software powered JavaScript that allows users to design, analyze, secure, and scale APIs anywhere with visibility and control. It allows developers and testers to access its features through different editors. This tool can work with large volumes of data APIs, making it ideal for complex and robust digital businesses. It can also identify performance issues by analyzing API traffic, response time, and possible error rates. 


  • With Apigee hybrid, users have the power to choose where to host their APIs—on-premises, Google Cloud, or hybrid. 
  • It easily creates API proxies from the Open API Specification and deploys them in the cloud.
  • It supports the creation and configuration of API packages, revenue models, reports, payment gateways, and developer portal integrations. 
  • This tool manages the process for designing, developing, publishing, deploying, governance, monitoring availability, and measuring performance.
Try PractiTest

#6. JMeter


Best for load and performance testing.

JMeter is open-source software for the load as well as performance testing. It is widely used for functional API testing. JMeter has many API testing functionalities and a bunch of features to make the process more efficient for testers. Developers can use this tool as a unit-test tool for the testing of JDBC database connections. 


  • It supports Command-line mode, which will be helpful for Java-compatible OS.
  • It enables the team to quickly create unique data (parameter values) for API tests with the help of CSV files.
  • It integrates with Jenkins, and users can include the API tests in CI pipelines
  • It can be used for both static resource performance testing as well as dynamic resources performance testing.
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#7. Assertible

Best for reliable API testing.

Assertible is another open-source API testing tool that continuously tests web services and concentrates on automation and reliability. Both developers and testers consider Assertible to be one of the best API testing tools. It puts a strong focus on reliability. This is because it supports API tests at all stages, from continuous integration to delivery pipeline.


  • It offers support that validates HTTP responses with turn-key assertions.
  • It is compatible with GitHub, Slack, and Zapier.
  • Its Sync feature allows users to update tests when their specifications change, so you don’t have to manually update tests after adding new parameters or changing the response of API.
  • This tool also supports running API tests after deployment.
Try PractiTest

#8. Karate DSL

Best for API testing, front-end UI testing, and performance testing.

Karate is a new open-source API testing tool based on the Cucumber library. It allows testers to write meaningful tests for web services using any domain-specific language. It helps testers create scenarios for API-based BDD tests in a simple and easy way without writing step definitions. These definitions have already been created by KarateDSL so that users can kickstart the API testing quickly.


  • It offers built-in JSON and XML assertions. It makes validating the responses from the API very easy.
  • With this tool, you don’t need to compile the code for executing the test cases. The test cases hit the endpoints directly and get the response.
  • It can run tests and generate reports like any standard Java project.
  • It uses Gherkins for defining test cases, therefore writing test cases in Karate is easy.
Try PractiTest

#9. Rest-Assured

Best for testing REST APIs using Java Libraries.

Rest-Assured is another open-source Java domain-specific language that makes testing the REST service simpler. It allows users to test REST APIs using java libraries and integrates well with Maven. 


  • It supports every HTTP method and various types of commands like POST, GET, PUT, DELETE, OPTIONS, PATCH, and HEAD.
  • You don’t necessarily need to code from scratch.
  • It also integrates with the Serenity automation framework.
Try PractiTest

#10. Swagger

Best for simplifying API development for users, teams, and enterprises.

Swagger is an open-source API testing tool that allows users to begin their functional, security, and performance testing from the Open API Specifications. It has helped millions of API developers, teams, and organizations deliver great APIs. It is the most powerful and easiest to use tool to take full benefit of the OpenAPI Specification.


  • Swagger Inspector allows you to inspect API response/responses and ensure they work as expected.
  • Swagger tooling and the ReadyAPI platform make it simple to rapidly create, manage, & execute API tests in your pipeline.
  • Users can create complex load scenarios to test the performance and scale of API.
  • All types of services are supported, from SOAP to GraphQL.
Try PractiTest

#11. ACCELQ 

Best for functional and codeless API test automation.

ACCELQ is an AI-powered codeless test automation and test management tool on the cloud. It is built on a cognitive core engine bringing the power of predictive analytics in scenario design, autonomics in test automation, and adaptive change management in traceability. IT teams and businesses of all sizes use this tool to accelerate testing by automating critical aspects of the lifecycle such as test design, planning, test generation, and execution.


  • It provides seamless CI/CD and Jira/ALM integration with natural traceability.
  • It offers API and UI Test Automation in the same simplified flow.
  • API Test Case Management, Test Planning, Execution and tracking governance
  • It directly correlates business processes and corresponding API for complete coverage.
Try PractiTest

#12. ReadyAPI

Best for API performance testing, API functional testing, virtualization, as well as API security testing.

Smartbear’s popular API testing tool, ReadyAPI accelerates functional, security, and load testing of RESTful, SOAP, GraphQL, and other web services right inside your CI/CD pipeline. It is more than a web service launcher. It can also analyze the results from a dashboard, which is useful for long processing times. ReadyAPI is an all-in-one tool that can assist with API performance testing, functional testing, virtualization, and API security testing.


  • It let users create comprehensive, data-driven functional API tests with or without scripts and add security scans with just a single click.
  • It supports the integration of API testing with the CI/CD pipeline.
  • You can eliminate dependencies in the testing pipeline by virtualizing RESTful, SOAP, TCP, JMS, and other web services.
Try PractiTest


API testing is a necessary part of the software development process. As more and more companies rely on APIs to communicate with other software applications, it becomes increasingly important that these APIs are tested thoroughly. Automation tools can help make this tedious task easier by taking over many of the tasks performed manually during API regression testing.

We’ve compiled this list of best API Testing Tools as an easy guide to help you decide on what might work best for your team or business.

Research Process

Total tools reviewed: 18
Total tools finalized: 12
Total time spent: 84 hrs

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