10 Best API Testing Tools in 2021 (SOAP and REST API Testing Tools)

List of the best free online API Testing Tools for Testing REST and SOAP APIs and Web Services:

Application Programming Interfaces (API) testing is a type of software testing where testing cannot be done at a front-end since there’s no GUI.

API testing has mainly performed the testing on the message layer and includes testing REST API’s, SOAP Web services, which could be sent over HTTP, HTTPS, JMS, and MQ. This now forms an integral component for any Automation Testing.

Due to the nature of API testing, it cannot be tested manually, and we need to opt for some API test tools for testing APIs. In this article, I have covered a list of some top API testing tools.

API Testing Tools

Importance of API testing through a test pyramid:

The ROI for the API testing will be higher when compared to the other testing types which are performed by the testers.

The below figure will give you the exact information on how much we need to focus on API Testing. As API tests are in the second layer, these are important and it needs 20% of testing efforts.

API Testing

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While testing an API, the focus should be on using the software in such a way in which the API will be called.

Hence, during testing, we need to check if the API will return the correct output under different conditions. The output in which the API returns is generally the pass or fail status, data, or a call to another API. For more accuracy and test coverage in API testing, data-driven testing should be performed.

In order to test the API, the testers prefer automation testing when compared to manual testing. This is because manual testing of API includes the writing of code to test it. API testing is conducted at the message layer as there is an absence of GUI.

Before you start API testing, you need to set up the test environment with a set of parameters. Configure the database and server as per the requirement. Then just like we perform smoke testing for an application, check the API by making an API call. This step will ensure that nothing is broken and you can continue for thorough testing.

The various levels of testing that you can perform for testing an API are Functionality Testing, Load Testing, Security Testing, Reliability Testing, API documentation Testing, and Proficiency Testing.

Points you should consider for API testing are as follows:

  • Target Audience or API consumer.
  • The environment in which the API is going to be used.
  • Testing aspects
  • Test for normal conditions.
  • Tests for abnormal conditions or negative tests.
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Top API Testing Tools (SOAP and REST API Test Tools)

Here are the top 15 best API Testing Tools (Research Done for you).

Comparison Chart:

Tool NamePlatformAbout toolBest ForPrice

Windows, Mac, Linux.It is the platform for the functional, security, and load testing of RESTful, SOAP, GraphQL, and other web services.Functional, security, and load testing of API and web services.It starts at $659/year.

cloud-based continuous testing Codeless API Test Automation, Seamessly Integrated with UI testingAutomates API testing with automated test design, codeless automation logic, complete test management, API regression planning & 360 tracking.Free Trial Available.
Pricing Starting from: $150.00/month that includes API, UI, DB, Mainframe automation
Katalon Studio

New Logo - Katalon Studio
Windows, macOS, LinuxA comprehensive API, Web, Desktop Testing and Mobile testing tool for beginners and experts.Automated testingFree license with paid support services

Linux, and
Chrome browser-plugin
It is an API development environment.API testingFree Plan
Postman Pro: $8 per user/month
Postman Enterprise: $18 per user/month

--Testing of REST services in Java domain.Testing REST API.Free

--It is the tool for the entire lifecycle of API.The tool is best for API designing.Free
Team: $ 30 per month for 2 users.

Let’s Explore!!

#1) ReadyAPI

ReadyAPI Price: The pricing options available with ReadyAPI are SoapUI (Starts at $659 per year), LoadUI Pro (Starts at $5999 per year), ServiceV Pro(Starts at $1199 per year), and ReadyAPI (Custom pricing. Get a quote). You can try the Ready API for 14 days for free.

ReadyAPI Tool

SmartBear provides the ReadyAPI platform for the functional, security, and load testing of RESTful, SOAP, GraphQL, and other web services.

In one intuitive platform, you will get four powerful tools, API functional testing, API performance testing, API security testing, and API & Web virtualization. This platform will help you to ensure end-to-end quality for all web services.

It provides flexible automation options for integrating API testing into your CI/CD pipeline during every build. You will be able to create comprehensive and data-driven functional API tests.


  • ReadyAPI can be integrated into any environment.
  • It has a Smart Assertion feature that can create bulk assertions against hundreds of endpoints quickly.
  • It provides native support for Git, Docker, Jenkins, Azure, etc.
  • It also supports Command-line for automated testing.
  • It supports parallel execution of functional tests and job queuing.
  • It provides features and functionalities for reusing the functional tests and generating realistic load scenarios.
  • ReadyAPI also provides features for removing dependencies during testing and development.

Best For: This platform works best for DevOps and Agile Teams. It is the best tool for the functional, security, and load testing of RESTful, SOAP, GraphQL, and other web services.

=> Visit ReadyAPI Website


ACCELQ – Codeless API Test Automation, seamlessly integrated with UI Testing.

ACCELQ Dashboard

ACCELQ is the only cloud-based continuous testing platform that seamlessly automates API and web testing without writing a single line of code. IT teams of all sizes use ACCELQ to accelerate their testing by automating critical aspects of lifecycle like test design, planning, test generation, and execution.

ACCELQ customers typically save over 70% of the cost involved in the change & maintenance efforts in testing, addressing one of the major pain points in the industry. ACCELQ makes this possible with AI-powered core to bring self-healing automation amongst other unique capabilities.

Design and User experience focus is at the heart of ACCELQ’s continuous innovation approach with a relentless effort to accelerate testing and improve delivered Quality for its customers.

Key Capabilities:

• Zero code API Test Automation on Cloud
• API and UI Test Automation in the same simplified flow
• API Test Case Management, Test Planning, Execution and tracking governance
• Dynamic Environment management
• Chain API Tests for true end-to-end validation
• Simple and Automated change impact analysis of API Test suite
• Regression suite planning with requirements tracking correlated with business processes
• Execution tracking with full visibility and defect tracking integrations
• Directly correlate Business process and corresponding API for complete coverage
• Seamless CI/CD and Jira/ALM integration with natural traceability
• No vendor lock, extendible framework open-source aligned

Best For: ACCELQ automates API testing with automated test design, codeless automation logic, complete test management, API regression planning & 360 trackings.

=> Visit ACCELQ Website 

#3) Katalon Studio


Katalon Studio is a robust and comprehensive automation tool for API, Web, Desktop testing and Mobile testing.

Katalon Studio provides easy deployment by including all frameworks, ALM integrations, and plugins in one package. The capability of combining UI and API/Web services for multiple environments (Windows, Mac OS, and Linux) is also a unique advantage of Katalon Studio among the top API tools.

Besides being a free solution, Katalon Studio also offers paid support services for small teams, businesses, and enterprises.

Feature highlights:

  • Supports both SOAP and REST requests various types of commands and parameterization functionalities
  • Supports the data-driven approach
  • Supports CI/CD integration
  • Supports AssertJ, one of the most potent assertion library, to create fluent assertion with BDD style
  • Suitable for both beginners and experts with the Manual and Scripting modes
  • Can be used for both automated and exploratory testing
  • Pre-built and customizable code templates
  • Sample projects are provided for instant reference
  • Auto-completion, auto-formatting and code inspection features for the code
  • UI to create, execute, and maintain tests

=> Visit Katalon Studio Website

#4) Postman

Price: It has three pricing plans.

For individuals and small teams, there is a free plan. The second plan is Postman Pro, which is for a team of 50 people. It will cost $8 per user per month. The third plan is Postman Enterprise, it can be used by the team of any size. The cost for this plan is $18 per user per month.


It is an API development environment. Postman API Development Environment is divided into three parts, Collections, Workspaces, and Built-in Tools. Postman collections will allow you to run requests, test and debug, create automated tests and mock, document, and monitor API.

Postman workspace will provide you the collaboration features. It will allow you to share the collections, set permissions, and manage participation in multiple workspaces for any team size. Built-in tools will provide the features which will be required by the developers to work with an API.


  • Helps in automated testing.
  • Assists in exploratory testing.
  • It supports Swagger and RAML (RESTful API Modeling Language) formats.
  • It supports knowledge sharing within the team.

Best For: The tool is best for API testing. It is rich in features, available for free, and has really good reviews from its users.

Website: Postman

#5) REST-Assured

Price: Free.


REST-Assured makes testing of REST services in the Java domain easy. It is an open-source tool. XML and JSON Requests/Responses are supported by REST-Assured.


  • Seamless integration with the Serenity automation framework.
  • It provides some baked-in functionalities.
  • It supports the syntax of BDD Given/When/Then.
  • To use the tool, it is not necessary to be an HTTP expert.

Best For Testing REST API.

Website: REST-Assured

#6) Swagger.io

Price: There are three plans for Swagger Hub, Free, Team, and Enterprise.

The price for the Team plan is $30 per month, for two users. For this plan, you can select the number of users as 2, 5, 10, 15, and 20. The price will increase as the number of users go up.

The third plan is an Enterprise plan. Enterprise plan is for 25 or more number of users. Contact the company to know more about this company.


The Swagger is a tool that will help you through the entire lifecycle of an API. This tool will allow doing a functional, performance, and security testing of API.

Swagger Inspector helps the developers and QAs to manually validate and explore the APIs in the cloud. Load and performance testing is performed through LoadUI Pro. It will allow you to reuse the functional tests of SoapUI. Swagger provides many open source tools.


Swagger provides the following features related to API:

  • API design and development
  • API documentation
  • API Testing
  • API Mocking and Virtualizations
  • API Governance and monitoring

Best For: Tool is best for API designing.

Website: Swagger.io

#7) JMeter

Price: Free


It is open-source software for load and performance testing of applications. It supports cross-platform. Jmeter works at a protocol layer.

Developers can use this tool as a unit-test tool for the testing of JDBC database connections. It has plugins based architecture. Jmeter can generate test data. It supports Command-line mode, which will be helpful for Java-compatible OS.


  • It will allow you to use various programming languages.
  • Load and performance testing of many different applications, servers, and protocols.
  • It allows you to replay test results.
  • It provides support for variable parameterization and assertions.
  • It supports per-thread cookies.
  • Configuration variables and a variety of reports are also supported by Jmeter.

Best For: Tool is best for load and performance testing of web applications.

Website: JMeter

#8) Karate DSL

Price: Free


It is an open-source framework for API testing. Karate framework is based on the cucumber library. With this tool, a tester can test web services by writing tests in a domain-specific language.

This tool is specially designed for automated API testing and is released by Intuit. To use this tool there is no need to have a programming language. But the basic understanding of HTTP, JSON, XML, XPath, and JsonPath will be an added advantage.


  • Multi-threaded parallel execution is supported.
  • It allows configuration switching.
  • Reports generation.
  • It supports reusing Payload-data for API testing.

Best For: It allows you to write tests in any language which can deal with HTTP, JSON, or XML.

Download Link: Karate DSL

#9) Airborne

Price: Free


Airborne is an open-source API test automation framework. It is a Ruby-based RSpec driven framework. This tool doesn’t have UI. It just provides the text file to write the code.


  • It can work with APIs which are written in Rails.
  • To use this tool, you must know Ruby and RSpec fundamentals.
  • It can work with Rack applications.

Download Link: Airborne

#10) Pyresttest

Price: You can donate the amount by creating an account on GitHub.


It is a python based tool for testing of RESTful APIs. It is also a Micro-benchmarking tool. For tests, it supports JSON config files. The tool is extensible in Python.


  • Return exit codes for failed results.
  • The building of test scenarios with generate/extract/validates mechanisms.
  • Because of minimal dependencies, it has easy deployment on the server which is helpful for smoke testing.
  • No code required.

Best For RESTful APIs.

Website: Pyresttest

#11) Apigee

Price: Apigee provides four pricing plans, Evaluation (Free), Team ($500 per month), Business ($2500 per month), Enterprise (Contact them). A free trial is also available for the tool.


Apigee is a cross-cloud API management platform.

It provides security and governance policies for all APIs. Using the open API specification, the tool allows you to easily create API proxies. With this tool, you can design, secure, analyze, and scale APIs anywhere.


  • It provides customizable developer portal.
  • It supports Node.js.
  • With the Enterprise plan, you will get advanced features like Apigee Sense advanced security, distributed network for low latency, Monetization for new business models, and traffic isolation.
  • With a Business plan, it provides the features of IP whitelisting, Java & Python callouts, distributed traffic management.
  • For the Team plan, it provides API analytics, Web service callouts, and some advanced policies like security, mediation, and protocol.

Best For API development.

Website: Apigee

Other TOP Free and Paid API Test Tools to Consider

12) Parasoft

Parasoft Logo

Parasoft, an API Testing tool helps in automated test case generation which can be reused and easily maintained and thus reduces a lot of regression effort. It supports end-to-end testing and has a very user-friendly interface.

Also supports multiple platforms like Java, C, C++, or.NET. This is one of the top recommended tools for API testing. It’s a paid tool and hence requires purchasing a license and then requires an installation before the tool can be used.

Official Website: Parasoft

13) vREST


An Automated REST API Testing Tool which can work on the Web, Mobile or Desktop applications. Its record and replay feature eases the test case creation. This Tool can be used to test applications hosted locally, intranet or the Internet. Some of its good features include supporting Jira and Jenkins integration and also allows imports from Swagger and Postman.

Official Website: vREST

14) HttpMaster

HttpMaster Logo

HttpMaster will be the right choice if you are looking for a tool that helps in Website testing as well as API testing. Other features include an ability to define global parameters, provides the user with an ability to create checks for data response validation by using the large set of validation types that it supports.

Official Website: HttpMaster

15) Runscope

Runscope Logo

An excellent tool for monitoring and testing API’s. This tool can be used for data validation of API’s to ensure correct data are returned. This tool comes with a feature of tracking and notifying in the case of any API transaction Failure, Hence if your application requires payment validation, then this tool can prove to be a good choice.

Official Website: Runscope

16) Chakram

Chakram Logo

This tool supports end-to-end test on JSON REST endpoints. This tool also supports third-party API testing. This tool can be a great help if you are looking for testing API’s that are still under development. This is built on the Mocha testing framework.

Official Website: Chakram

17) Rapise

Rapise Logo

This tool comes with an extensive feature list that satisfies different types of testing needs, one of them being the API testing. This supports testing SOAP Web services as well as REST web services. In addition, it allows testing different types of DLL API’s ranging from managed i.e. written using .NET framework to unmanaged written using native Intel x 86 codes.

Official Website: Rapise

18) API Inspector

API Inspector Logo

API Inspector, a tool from Apiary allows for monitoring the API during the design phase by capturing both request and response and lets user views them Apiary.io or Apiary editor allows the user to write API blueprints.

Official Website: API Inspector

19) SOAP Sonar

Soapsonar Logo

SOAP Sonar is the Service and API Testing tool owned by one of the leading API tool developing company Crosscheck Network. Tools allow testing by simulating HTTPS, REST, SOAP, XML, and JSON. Other tools from the same brand are CloudPort Enterprise which is mainly used for Service and API Emulation, and Forum Sentry, a tool for securing API’s.

Official Website: SOAP Sonar

20) API Science

API Science Logo

API Science, an excellent API monitoring tool, comes with a feature to monitor Internal as well as External API’s. This tool lets the user know if any API ever goes down, so necessary action can be taken to bring it back up. Important features include excellent API diagnostics, user-friendly dashboard, alert and notification system, powerful reporting and supports JSON, REST, XML, and Oauth.

Official Website: API Science

21) API Fortress

APIFortress Logo

From testing perspective what do you really check in an API tool, it should let you know if API is up and running and second is on the response time.API fortress satisfies both the requirement and proves to be a very good API testing tool. This allows a Full API testing including regression test and like all other tools comes with features like SLA monitoring, alerts, and notification, reporting.

Official Website: API Fortress

22) Quadrillian

It’s a web-based REST JSON API testing tool. It lets user follow a structure by creating a project, then a test suite and then create and create/place the test cases. It lets creation & sharing of the test suite using browser. The tests can be run on the website or can be downloaded.

Official Website: Quadrillian

23) Ping API

It’s an automated API monitoring and testing tool. Very easy to use, lets the user create a test case using JavaScript or Coffee Script, run tests and also has a feature where tests can be scheduled. For any failures, the user gets notified through email, Slack and Hipchat.

Official Website: Ping API

24) Fiddler

Fiddler is a free debugging tool from Telerik. This tool is mainly used to monitor the network traffic between a computer and the internet. This works well on any browser, any system, and any platform. It’s also one of the best security testing tools for web applications because of the technique it uses for decrypting HTTPS traffic. Official Website: Fiddler

25) WebInject

WebInject is a free tool used for testing web applications and web services. This is written in Perl language and for running this on any platform, a Perl Interpreter is required. This tool uses an XML API for creating test cases and generates HTML and XML report which includes pass/fail status, errors, and response times. Overall it’s a good tool. Official Website: WebInject

26) RedwoodHQ

This is an open-source tool that helps to test API SOAP/REST and supports multiple languages like Java/Groovy, Python, and C #. This tool supports multi-threaded execution, also allows the user to compare the results from each of the runs. Official Website: RedwoodHQ

27) API Blueprint

API Blueprint is an open-source tool for API Developers and Testers. The tool uses very simple syntax and also makes testing easy for testers. Official Website: API Blueprint

28) REST Client

It’s a Java application that supports testing RESTful web services and this can also be used to test different types of HTTPs communications. Official Chrome extension: REST Client

29) Poster (Firefox Extension)

This Add-on lets the user set their Http requests by interacting with web services, and generates results which can be verified by the user. Official Website: Poster (Firefox Extension)

30) API Metrics

A very good tool for API monitoring. It supports running API calls anywhere and comes with a very good analytical Dashboard. Official Website: API Metrics

31) RAML

RAML helps users by generating a lot of tests after the user has specified the HTTPS REST API. This tool is well integrated with other testing tools like Postman, Vigia and lets a user import tests from RAML to these tools. Official Website: RAML

32) Tricentis Tosca  

Tosca, a model-based test API automation testing tool from Tricentis but also supports API testing. Official Website: Tricentis Tosca


In this article, we have covered the information about API testing, and a list of top API testing tools.

Out of these top tools, Postman, SoapUI, Katalon Studio, Swagger.io provide free and paid plans. Whereas REST-Assured, JMeter, Karate DSL, and Airborne are open source tools and are available for free.

Hope you will find this detailed comparison of the best API test tools helpful.

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