20 Best API Testing Tools in 2021: REST & SOAP Web Services

An API or Application Programming Interface is a collection of software functions and procedures through which other software applications can be accessed or executed. In API Testing you use software to send calls to the API, get output and log the system’s response. For Agile development, Api Testing becomes important as shorter development cycles put more pressure on automated testing.

Here is a list of top Web Services Testing API Tools. The list contains both open-source(free) and premium web API testing tools.

API Testing Framework | API Automation Tools

Name Price Link
Katalon Studio Free + Paid Plan Learn More
Parasoft SOAtest Free + Paid Plan Learn More
Postman Free + Paid Plans Learn More

1) Katalon Studio

Katalon Studio brings a hassle-free API testing platform for testers with or without prior programming experience.


  • Supports all types of REST, SOAP requests, SSL client certificate.
  • Easily import tests from Swagger (2.0 & 3.0), Postman, WSDL, and WADL.
  • Built off of data-driven testing methods better test coverage and reliability.
  • Create fluent assertions in BDD style with AssertJ support.
  • Support set up API test data using UI testing.
  • Provide insightful test report dashboards of all testing stages for better monitor and collaboration across teams.

2) Parasoft SOAtest

Build a foundation of automated tests that can be executed as part of your continuous integration and DevOps pipelines. Parasoft SOAtest automates the continuous testing of complex systems by creating codeless API test scenarios from manual recordings. SOAtest efficiently transforms your test artifacts into security and performance tests, increasing reusability and reducing redundancy.


  • Automatically generate codeless API tests that are robust, reusable, and easily shareable.
  • Leverage artificial intelligence to create powerful test scenarios in less time than other tools.
  • Keep test assets in sync with evolving systems via automation.
  • Seamlessly integrate with load testing and service virtualization.

3) Postman

Postman is a plugin in Google Chrome, and it can be used for testing API services. It is a powerful HTTP client to test web services. For manual or exploratory testing, Postman is a good choice for testing API.

  • With Postman, almost all modern web API data can be extracted
  • You can write Boolean tests within Postman Interface
  • You can create a collection of REST calls and save each call as part of a collection for execution in future
  • Unlike CURL, it is not a command line based tool, which makes this tool hassle free of pasting text into command line window
  • For transmitting and receiving REST information, Postman is more reliable

4) Tricentis

Top 20 API Testing Tools

Tricentis is a robust web services testing tool. Prominent API Testing features of Tricentis Tosca are –

  • This web services test tool supports a wide array of protocols including HTTP(s) JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ,NET TCP
  • It integrates into the Agile and DevOps Cycle
  • It is one of the best api automation tools which uses model-based test automation that makes script maintenance easy.
  • Enables end-to-end testing as API tests can be used across mobile, cross-browser, packaged apps, etc.

Tricentis’ 400+ customers include global names from the Top 500 brands such as ExxonMobil, HBO, Whole Foods, Toyota, Allianz, BMW, Starbucks, Deutsche Bank, Lexmark, Orange, A&E, Vantiv, Vodafone, Telstra and UBS.

Download link: https://www.tricentis.com/software-testing-tool-trial-demo/


Top 20 API Testing Tools

The most widely popular tool for API testing in the world, SoapUI allows you to test REST and SOAP APIs with ease – as it has been built specifically for API testing.

  • Quick and Easy Test Creation: Point-and-click, drag-and-drop, functionality makes complicated tasks (like working with JSON and XML) simple
  • Powerful data-driven testing: Load data from Excel, files, and databases to simulate the way consumers interact with your APIs
  • Reusability of Scripts: Reuse your functional test cases as load tests and security scans in just a few clicks
  • Seamless Integrations: Integrates with 13 API management platforms, supports REST, SOAP, JMS, and IoT

SoapUI Pro is used by thousands of leading companies around the world, including: Apple, Microsoft, Cisco, Oracle, HP, NASA, eBay, MasterCard, Intel, FedEx, and Pfizer

Download link: https://smartbear.com/product/ready-api/soapui/overview/


It provides an extensible framework helpful in executing and building the functionality of headless system that do not have a user interface. It is one of the best api testing tools that helps to test the headless technologies like Databases and Webservices, JMS, etc. By using the API test conversion tool, you can convert soapUI tests to UFT (QTP) API tests.

Download QTP

7) vREST

vREST API testing tool provides an online solution for automated testing, mocking, automated recording and specification of REST/HTTP APIs/RESTful APIs.

  • It provides an exhaustive tool to quickly validate your REST APIs
  • This rest api test tool delivers zero defect web applications with less effort in API testing
  • To validate your web application no skilled resources are required, and it can generate documentation for your API specifications
  • API mocks can be created in vREST with the help of Mock Server Functionality. User can directly start developing frontend using mock HTTP requests

Link to Vrest

8) HttpMaster

It is a web development tool to automate web application testing, including API testing, service testing and website testing. It is one of the best web api testing tools primarily used as web API test tool to automate testing of web API calls.

HttpMaster is a best choice for API testing as it has got

  • Several http methods (GET, POST, DELETE etc.)
  • Dynamic parameters of various data types to make batches of different API requests
  • Various validation types and advanced validation expressions

Download HttpMaster

9) Ping API

Ping-API is API testing allows to write test script in JavaScript and CoffeeScript to test your APIs. It is one of the best api testing tools which allows inspecting HTTP API call with a complete request and response data. For any failures, the user gets a notification through email, slack or Hipchat.


  • Ping- API to schedule test in every minutes or hour
  • Support for writing script to set request headers, body and URL parameters. It supports for writing script to validate response headers and body
  • It is one of the best api tools that validates CRUD flow and log in to Ping API

Download link: https://ping-api.com/

10) Rest-assured

It’s a popular rest api testing framework to test REST services in Java.

Learn more about Rest-Assured

11) Karate DSL

Karate is a new API testing framework base on cucumber library. Karate DSL allows testers to write meaningful tests for web service using a domain-specific language.


  • It supports configuration switching/staging, multi-threaded parallel execution
  • Allows testing and generating reports just like any standard Java Project
  • Possible to write tests even for the non-programmers
  • The karate API testing tool allows re-use of payload-data and user-defined functions across tests.

Download link: https://github.com/intuit/karate

12) Rest Console

HTTP client and Request visualizer and constructor REST API testing tool. It is one of the best api testing tools which helps developers to build, debug and test RESTful APIS.


  • Construct POST or PUT body via raw input
  • Easy query parameters creation
  • Add custom headers through intuitive UI
  • Keyboard navigation and shortcuts

Download link: https://github.com/ahmadnassri/app-restconsole

13) Hippie-Swagger

Hippie-swagger is a tool for testing APIS. It is one of the best api testing tools which supports a clear assertion syntax, for extending test behavior. It also allows clean printing reports.


  • It will fail test whenever swagger documentation is either erroneous or missing
  • Readable and accurate assertation messages
  • Validated parameters, request, response, pats, etc.

Download link: https://github.com/CacheControl/hippie-swagger

14) Pyresttest

PyRestTest is a Python-based REST API testing platform. It supports tests in JSON or YAML config files. Therefore, there is no code needed.


  • It’s minimal dependencies, which allows easy deployment on-server for smoke tests/health checks
  • This REST API test tool will return exit codes on failure
  • Pyresttest allows to generate/extract and validate mechanisms to build test scenarios

Download link: https://github.com/svanoort/pyresttest

15) Airborne

Airborne is one of the best API automation tools used by rest API tester for testing Rest APIs.


  • Airborne is a programming and rest api testing framework, so it has no user interface apart from the text file to create code
  • To use airborne, you just need to remember a few key methods in the toolset and some ruby and rspec fundamentals

Download link: https://github.com/brooklynDev/airborne

16) JMeter

JMeter is used for functional API testing which includes needed to test an API. It is one of the best api testing tools which has features which help to boost the performance of API testing.


  • It can be used for both static as well as dynamic resources performance testing
  • It supports replaying of test results
  • It can automatically work with CSV files. This helps test team to produce unique parameter values for API tests

Download link: http://jmeter.apache.org/

17) APIpray Inspector

Apiary allows monitoring the API during the design phase by capturing both request and response. It allows the user to write API blueprints and lets the user view them Apiary editor or Apiary.jo.


  • Role-based access control over API documents.
  • It allows to add and remove team members from API design projects
  • API Blueprint management dashboard

Download link: https://apiary.io/

18) SOAP Sonar

SOAPSonar is an API testing and diagnostics platform for SOAP, XML, REST-based web services. Use external sources like Excel, MS SQL, Oracle or any ODBC Database for automated tests.


  • This web services test tool identifies Web Services vulnerabilities like Malware Threat and SQL Injection
  • Web Service Functional Testing with Success Rule Framework and Concurrent Client Load Testing
  • Native HP QC Integration, and supports integration with Hudson, Ant, and JUnit

Download link: http://www.crosschecknet.com/

19) API Science

API science allows monitoring the health, availability, and performance of web APIs. It is one of the best api testing tools that enables monitoring Private, Partner and Public APIs. This tool allows the user to know if any API ever goes down so that needed action should be taken to bring it back up.


  • It is multi-step & Powered by JavaScript
  • Powerful reporting mechanism helps to get insights into historical trends and spot future issues.
  • Supports JSON, REST, XML, and Oauth
  • Helps to manage API supply chain

Download link: https://www.apiscience.com/

20) Apigee

Apigee is a cross-cloud API testing tool. It allows the user to measure and test API performance, supports and build API using other editors like Swagger. It offers security and governance policies across all APIs.


  • Allows to design monitor, deploy, and scale APIs
  • Easily create API proxies from the Open API Specification and deploy them in the cloud
  • Identify performance issues by tracking API traffic, error rates, and response times

Download link: http://apigee.com/


❓ What is API?

An API or Application programming interface is a collection of software functions and procedures through which other software applications can be accessed or executed.

✅ Which are the Best API Testing Tools?

Here are some of the Best API Testing Tools:

  • Katalon Studio
  • Parasoft SOAtest
  • Postman
  • Tricentis
  • HP QTP
  • vREST
  • HttpMaster

⚡ What is the importance of API testing in agile development?

For Agile development, API Testing becomes important as shorter development cycles put more pressure on automated testing.

🌟 What are the general features of API testing tools?

The general features of API testing tools are:

  • Exhaustive features to quickly validate your REST APIs.
  • Support various validation types and advanced validation expressions.
  • Enables you to write tests even for the non-programmers.
  • It has easy to use UI.

💥 What are the benefits of API?

The important benefits of API are:

  • Companies can update the workflow to become more productive.
  • It helps you to personalize user experience.
  • Organizations can customize the service with ease.
  • Content can be embedded from any application or site.