Best API Testing Tools in 2020

Timothy Joseph
Timothy Joseph | July 21, 2020

Best API Testing Tools in 2020

Every QA engineer can agree that API testing tools are very important when overcoming the common challenges that API testing presents. Yet strong opinions surface when debating which is the best tool to use when following API testing automation best practices.

The solution is simple - choose the API testing tool that fits the specific needs of your product, your team and your development cycle. Yet the question remains the same - which API testing tool is the best fit for your product?

There’s a lot we need to unpack before you can make this decision. What are API testing tools? How should your team choose an API tool? And is there an API testing tool list that can streamline this decision-making process?

We compiled this API testing tool comparison so that your team can expedite your decision based on facts, not hype.

What Are API Testing Tools?

API testing tools are technology solutions designed to effectively carry out the testing of the application programming interface of your software product. API performance testing tools assist in the API testing process by determining if APIs correctly respond to requests, maintain high security standards and perform as expected.

API testing examines the behavior of your software’s user interface (UI) without interacting or loading the UI. With API integration tools, your team can receive accurate data and speedier test results throughout the testing process so that bugs and defects are detected and resolved prior to production deployment.

Best API Testing Tools

Having the right API testing tools in place is now more important than ever. We recommend that you consider these solutions within our API testing tool comparison below.

  • Postman

    Do you need API testing tools that don’t require your QA team to use the same language as your developers? Postman can provide that experience as well as support various levels of API testing.

    Once a Chrome browser plugin, this solution now extends with the native version for both Windows and Mac.

    Unlike other API integration tools within this API testing tool comparison guide, Postman offers three plans:

    • Free version for individuals and small teams
    • Pro plan for teams up to 50 people
    • Enterprise plan for teams of any size


    • Doesn’t require learning a new language
    • Designed for easy knowledge sharing across teams by packaging all requests and expected responses for sending.
    • Easy-to-use Rich interface
    • Easy-to-use REST client
    • Supports automated and exploratory testing
    • Has Run, Test, Document and Monitoring Features
    • Dozens of integrations like support for Swagger & RAML formats
    • Runs on Mac, Windows, Linux & Chrome Apps
  • SoapUI

    Add SoapUI to your API testing tools when your team needs a functional testing tool for SOAP and rest testing. It’s a great option when your team doesn’t want to create complicated API tests from scratch in a single test environment. SoapIU offers a free plan as well as a Pro package.


    • Easy-to-use graphical interface
    • Drag and drop test creation
    • Capable of complex test scenario creation
    • Allows for asynchronous testing
    • Supports custom workflows or functionalities
    • Mock service for mimicking web services before final implementation
  • REST Assured

    Testing REST service is simplified with REST-assured. Add this solution to your API testing tools if your team is comfortable working in an open-source Java library that provides a domain-specific language (DSL) for writing strong, reusable tests and validating complex responses.


    • HTTP expertise not required
    • Dozens of set-up functionalities so your team doesn’t need to code from scratch
    • Support BDD Given/When/Then syntax
    • Easily integrates with Serenity automation framework
  • Katalon Studio

    Katalon Studios is considered one of the best API integration tools because of its comprehensive end-to-end automation solution applicable for both testers and developers. A unique advantage of this solution in comparison to other tools featured on this API testing tool list is its capability of combining UI and API/Web services for multiple environments, including Mac, Windows and Linux.


    • Support both SOAP and REST
    • Allows for API, WebUI, Desktop App and Mobile testing 
    • Testers can execute automated and exploratory tests
    • CI/CD integration
    • Support AssertJ for creating fluent assertion with BDD style
    • Sufficient for both experts and non-technical users through Manual and Groovy Scripting modes
  • JMeter

    Initially created for load testing, JMeter has evolved into one of the best free API testing tools for functional API testing. With a variety of features and API testing functionalities, this solution is designed to support efficient API testing practices.


    • Supports static and dynamic resources performance testing
    • Allows teams to replay test results
    • Compatible with CSV files for quick creation of parameter values for API testing
    • Easy integration with Jenkins makes it possible to include API tests in the CI pipelines
  • Tricentis Tosca

    Agile and DevOps teams find it essential to add Tricentis Tosca as one of their API testing tools to support their development cycle. This solution provides users a no-code, automated continuous testing platform.


    • Designed for the Agile and DevOps Cycle
    • Supports most common protocols, including HTTP(s) JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ and NET TCP
    • Model-based test automation maximizes test reuse and maintainability
    • API tests can be used across mobile, cross-browser and packaged apps
    • Aims to reduce regression testing time
    • Ability to execute manual testing and collect results without environment configuration
  • Karate

    Considered one of the most mature solutions in free API testing tools, Karate makes our API testing tool list because it allows users to create scenarios for API-based BDD tests easily without writing step-to-step definitions.


    • Foundation of Cucumber-JVM
    • Java knowledge not required for creating tests
    • Easy test creation process for non-technical users
    • Runs test and generate reports in accordance to standard Java procedure
    • Supports configuration switching and multi-threaded parallel execution
    • Reusability of payload-data for API testing
  • Apigee

    As one of the best cross-cloud API testing tools. Apigee allows users to measure and test API performance as well as build out APIs using editors such as Swagger.


    • Design, monitor, deploy and scale APIs
    • Identify performance problems by tracking API error rates, response times and traffic
    • Multi-step solution powered by JavaScript
    • Easy creation of API proxies from the Open API Specification deployable to the cloud
    • Deployment models of cloud, on-premise, or hybrid on a single code base
    • Provides customizable developer portal
    • Supports Node.js, PCI, HIPAA, SOC2, and PII for apps and APIs
  • Assertible

    Add Assertible to your API testing tools for its automation structure and test reliability. This solution is known for its encryption features of storing tokens, passwords and secret data fields required by tests in order to approve your API testing security practices.


    • API test automation through step-by-step, continuous integration and delivery pipeline
    • Runs API tests after deployments and integrates with common tools including Slack, GitHub and Zapier
    • Supports validating HTTP responses with turn-key assertions like JSON Schema validation and JSON Path data integrity checks
    • Ability to update tests when specifications change
  • Swagger

    Include Swagger to your API integration tools so that your team can start their functional, performance and security testing from Open API Specifications. With Swagger tooling and Ready API platform, users find this solution easy to create, manage and run API tests in the pipeline.


    • Provides capabilities to inspect API request-responses and ensure they perform as expected
    • Imports user API definitions for easy validation of schema rules and automatic generation of assertions against endpoints
    • Generates complex load scenarios for testing the performance and scale of APIs
    • Support all types of services from REST, SOAP to GraphQL

How to Choose an API Testing Tool

Follow the facts. Review the options highlighted within this API testing tool comparison so that your new technology solution supports all best practices as recommended within this API testing checklist. You can further simplify the decision-making process when it’s time to choose an API testing tool by asking the right questions:

  • Is the tool easy to use for all expected users?
  • Does the tool feature functionalities beneficial and relevant to your team’s needs?
  • Does the tool provide optimized workflows?
  • Does the tool support all necessary formats and industry-specific protocols?
  • Does the tool streamline the API test automation process?
  • Is the tool easy to manage and maintain?

Need more help during the API testing process than this API testing tool list can provide? Receive the assistance you need by partnering with a QA services provider like QASource. Our team of engineers and testers have years of experience with API testing and can help your team implement best API testing practices within your development cycle. Get a free quote today.


This publication is for informational purposes only, and nothing contained in it should be considered legal advice. We expressly disclaim any warranty or responsibility for damages arising out of this information and encourage you to consult with legal counsel regarding your specific needs. We do not undertake any duty to update previously posted materials.