API testing is a type of software testing that focuses on determining if APIs meet expectations. As APIs are becoming the essential component of software development, it is necessary for developers and programmers to perform API tests. This testing cannot be performed on the front-end as there is no Graphic User Interface for APIs. Below, we’ve analyzed 25 API testing tools, outlining their pros and cons.

1. RapidAPI

The list of best API testing tools starts with RapidAPI. RapidAPI is the largest API marketplace over a million developers use to find, test, and connect to thousands of APIs, all with a single account. On RapidAPI, you can collaborate on APIs using RapidAPI for teams with external and internal APIs. Developers can use RapidAPI Testing on their internal APIs too with RapidAPI Teams or using RapidAPI Hub.

Pros:

• • It is free to use.

• You can test as many APIs on the marketplace as you want.
• One workspace for 10,000 public APIs.

2. REST-assured

REST-assured is considered as one of the best tools for testing APIs in Java. Rest-assured is an open-source platform with a Java Domain-specific language. The Rest-assured API was created so that you don’t need to be an expert in HTTP to test web APIs.

Pros:

• You don’t have to be an HTTP expert.
• You don’t have to code things from scratch as it comes with some inbuilt functions.
• It supports the syntax of Behaviour Driven Development (BDD) testing – Given/When/Then.

Cons:

• It supports only the Java language.
• It does not support SOAP APIs explicitly.

3. Postman

After REST-assured, the next API testing tool is Postman. Postman offers a web version as well as a desktop app, and can also be used for testing API services. It enables the user to easily share the knowledge with the team.

Pros:

• This tool is easy to use compared to others.
• Easy to set-up parameters on method calls.
• Ability to store commands.
• It offers API development capabilities as well.

Cons:

• Pricing for enterprise is high.
• Enterprise version is easy to set up and use, but the number of requests is limited.
• It’s not possible to test more than one API simultaneously.

4. Paw

Paw is another beautiful API testing tool specially designed for Mac. Either you are an API maker or consumer, Paw helps you to build HTTP requests, inspect a server’s response, and even generate client code.

Pros:

• It is easy to use.
• It has an excellent interface.
• It is more stable in performance as compared to other API testing tools.
• It also has multi-dimensional environment settings.

Cons:

• Currently, Pas is available for Mac users only.
• High pricing (one-time purchase).

5. SoapUI

SoapUI is another on-prem API testing tool that allows developers to test REST, SOAP, GraphQL, and Web Services. SoapUI Pro gives development and testing teams a powerful solution to create, run, and analyze complex tests on web services. SoapUI boasts a lot of unique features like test reports, SOAP API testing, and others.

Pros:

• It can create custom codes using Groovy.
• You can transfer data from one response to multiple API calls without manual intervention.
• It stores your work so that you can revisit it at a later time.

Cons:

• Not helpful with Web UI Testing and mobile app testing.
• This tool lacks documentation.
• Saving projects can be a little confusing for beginners.

6. Katalon Studio

Katalon Studio is another free API testing tool for API, Web, Desktop App, and Mobile applications. It provides easy development by including all frameworks and plugins in one package. It is suitable for both beginners and experts with the Manual and Scripting modes.

Pros:

• Katalon supports SOAP and RESTful requests.
• It can be used for automated and exploratory testing.
• It supports CI/CD integration.
• It is a complete package and framework.

Cons:

• It is difficult to troubleshoot issues.
• It is hard to debug code, and there are no compile-time error checks.
• It does not have support for distributed testing.

7. JMeter

Apache Jmeter is another open-source software for load and performance testing of applications. It is widely used for functional API testing. It comes with many API testing functionalities and a bunch of features to make the process more efficient.

Pros:

• JMeter can be utilized in static and dynamic resource performance testing.
• It allows developers to replay test results.
• The interface of JMeter is user-friendly and can be used in a command-line interface.
• JMeter supports per-thread cookies.

Cons:

• It requires skilled testers.
• It doesn’t support Javascript and, by extension, doesn’t automatically support AJAX requests.
• Memory consumption is high in GUI mode, which causes it to give out errors for many users.

8. Karate DSL

Karate DSL, based on the Cucumber library, helps create scenarios for API-based BDD tests in a simple way without the need to write. It combines API test-automation, mocks, and performance-testing into a single, unified framework. It allows testers to create meaningful tests for web services using a domain-specific language.

Pros:

• Karate DSL supports multi-thread parallel execution.
• It allows configuration switching.
• Karate DSL is a good option for testing GraphQL.
• It supports XML as well as JSON.

Cons:

• The tool doesn’t have Auth schemes out of the box.
• There is no ‘Find Usage’, auto renaming.
• Code support becomes very time consuming and expensive.

9. Tricentis Tosca

Another best API testing tool is Tricentis Tosca. If you are looking for a continuous testing platform for Agile and DevOps, you may consider this one. It supports many arrays of protocols like HTTP(s), JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ, NET TCP.

Pros:

• Tosca reduces the time of regression testing.
• The excellent results and dashboards give a nice view into results.
• The API tests can be used across mobile, cross-browser, packaged apps, etc.
• It maximizes reuse and maintainability with model-based test automation.

Cons:

• Image comparison and visual validation are important, yet Tricentis doesn’t support these.

10. Assertible

Assertible is another open-source tool with GitHub forks. It mainly focuses on automation and reliability. The sync feature in Assertible allows testers to update their tests when their specifications change. In the recent update, Assertible got a new feature called Encrypted variables.

Pros:

• It provides an easy way to create robust tests.
• It will help you to reduce bugs in your application by allowing you to develop an automated QA system.
• Assertible allows users to get a higher level of insights on their website’s services’ health.

Cons:

• The platform might not be convenient if you like viewing a detailed quality report of your web services.

11. Apigee

Apigee is another useful tool for API testing. Apigee, part of Google Cloud, offers API management features. Apigee allows users to measure and test API performance and support and build APIs using other editors like Swagger. Apigee is purpose-built for digital business, and the data-rich mobile-driven APIs and apps that power it.

Pros:

• It identifies performance issues by tracking API traffic, error rates, and response times.
• It supports Node.js
• It is straightforward to control.
• It is multi-step and powered by JavaScript.

Cons:

• Prohibited from using JSON.stringify on Apigee objects (tokens).
• Only one user can be active in a proxy at a time.
• UI allows users to add target servers, but users must utilize the API to turn on SSL.

12. RestSharp

RestSharp is another testing solution that you can use for API testing. It allows you to develop .Net APIs and testing them with the same tool. RestSharp becomes very handy for Windows developers using REST or SOAP APIs to communicate with external data.

Pros:

• It is easy to use.
• Supports both asynchronous and synchronous requests.

Cons:

• Lacks strong developer tools.
• Can only work with .Net based applications

13. API Fortress

API Fortress is arguably the most powerful API testing and monitoring solution for REST and SOAP APIs. It satisfies many requirements and proves to be a worthy API testing tool. API Fortress allows full API testing, including regression testing. Like other tools on the list, it comes with SLA monitoring, alerts, notifications, and reporting.

Pros:

• It enables Automated tests as part of a CI pipeline.
• Robust notification and data integrations.
• Continuous monitoring for APIs, as well as load testing.
• Simple one-click automation. Test during development and deployments (CI/CD), and monitor functional uptime.

Cons:

• No free pricing tiers.
• Limited options for creating API tests using code.

14. Airborne

Airborne is an open-source Ruby-based RSpec-driven API testing framework. This tool doesn’t have a UI. It just provides the text file to write the code. It can work with Rack applications. To use Airborne, you just need to remember a few key methods in the toolset and some Ruby and RSpec fundamentals.

Pros:

• It can work with APIs written in Ruby on Rails.
• Works with Rack applications like Sinatra and Grape.

15. HttpMaster

HttpMaster is a development and test tool for REST web services and web API applications. It is a universal HTTP tool that can also be used to develop other web application types, for example, for testing HTML forms. It also has an elegant and easy-to-use interface, small and compact installation package, and does not require advanced technical skills.

Pros:

• You can use request chaining to leverage request items to include some data from the previous request with the next request.
• Automated API app testing.
• Automated RESTful service testing.
• Parallel Execution.

Cons:

• Supports Windows only.
• No JSON formatting support.

16. PyRestTest

PyRestTest is a python-based REST testing and API micro-benchmarking API testing tool. For tests, it supports JSON config files. The tool is extensible in Python. For a failed scenario, it returns an exit code, which can be converted into pursuable logs. In short, it returns exit codes on failed results.

Pros:

• PyRestTest is an easy tool to use.
• It can support many add-ons.
• No code is required.
• It has minimal dependencies, which allows easy deployment on-server for smoke tests/health checks.

Cons:

• Synchronization issues with generators, etc.
• Process management and similar headaches.
• May not use networking as efficiently as CurlMulti does.

17. Unirest

Unirest is a library to simplify making HTTP REST requests. It is one of the highly preferred API automation testing tools. It’s open-source and available in multiple languages. Unirest has its own documentation page where you can find all the different REST methods. It supports everything you need to start consuming APIs both on Rakuten RapidAPI and abroad.

Pros:

• Unirests supports eight languages such as Node, Ruby, Java, Python, and Objective C.
• Unirest can combine with XUNIT or BDD runner.
• It includes a documentation page for reference.

Cons:

• No in-built library for Matchers/ Extractors / Assertions.
• Simple HTTP Client Library.

18. ReadyAPI

ReadyAPI is a popular API testing tool by Smartbear. ReadyAPI is not just a web service launcher, but a tool that can analyze results from a dashboard — helpful for requests with long processing periods. ReadyAPI is a four-in-one tool assimilating API performance testing, API functional testing, API virtualization, and API security testing.

Pros:

• It ensures complete quality checks for all the web services.
• Supports integration of API testing with CI/CD pipeline.
• Removes dependencies.
• Parallel execution of functional tests and job queuing.

Cons:

• Interface is not the best.
• Performance and memory management both need to be improved.

19. AccelQ

AccelQ is an agile testing platform for functional and API test automation. AccelQ is a cloud-based continuous testing podium for API automation testing. It assists in API testing without even writing a single code. It supports chain API tests for complete testing.

Pros:

• Dynamic environment management.
• It has Defect tracking.
• Links business process with matching API.
• Open-source aligned.

Cons:

• High Cost
• Delivery schedule and releases are also pretty aggressive.

20. RoboHydra Server

RoboHydra Server is a perfect API testing tool for users who don’t have a server but require one. It is a testing tool for HTTP-based clients (i.e., software that makes HTTP requests). It can manage GUIs for mobile applications, public APIs, and complex Java-based programs.

Pros:

• RoboHydra is very versatile.
• It allows connecting clients-under-test to it and run the tests.
• Can test any HTTP, HTTPS, or WebSockets client.
• Written in JavaScript, runs under Node.

21. WebInject

WebInject is another open-source solution for automated testing of web applications and web services. WebInject is a trusted API testing tool — it creates fully automated test suites for functional, regression, and acceptance testing.

Pros:

• Collects and analyses the result to prepare an automated report.
• Written in Perl can be installed on MS Windows, GNU/Linux, BSD, Solaris, Mac OS.
• It can function on different platforms using PERL interpretation.

22. Appium

Appium has one primary purpose — to test mobile applications — but that does not mean that it has limited options. It is one of the open-source automated testing tools primarily intended for mobile applications. It backs automation of native, hybrid, and mobile web applications built for iOS and Android. Appium has gained immense popularity and stability, thereby emerging as one of the best mobile automation testing tools.

Pros:

• It supports multiple programming languages like Java, Python, Ruby, C#, etc.
• It uses WebDriver API, so it makes it easy to use for former web test automation engineers.
• Open Source: It’s such a nice strength for Appium.
• Handles the connection between Appium’s server and Xcode’s tools during execution well.

Cons:

• Appium running is a bit slow, compared to tests written with Appium and Espresso or XCTest.
• Challenging for a new user to take on without guidance from a veteran
• Documentation can be confusing.
• A skilled automation tester is required to build the quality code for automating mobile test cases.

23. RedwoodHQ

RedwoodHQ is an open-source tool that helps test API SOAP/REST and supports multiple languages like Java/Groovy, Python, and C#. It uses a web-based interface designed to run tests on an application with numerous testers. For developers, this performance testing tool may prove to be too shallow.

Pros:

• It allows the user to compare the results from each of the runs.
• Open-Source test automation framework.
• Connecting to open-source Automation tools, like Selenium, Appium, Silk4J, etc. to do any UI automation you want.

Cons:

• Still except for defects, the system is not complete, and still not ready for production.
• It is open-source, but on the same side, very versatile and high level.

24. Fiddler

Fiddler is a free web debugging proxy for any browser, system, or platform. It helps you debug web applications by capturing network traffic between the Internet and test computers. Fiddler lets you monitor, manipulate, and reuse HTTP requests. The tool is mainly used to monitor the network traffic between a computer and the Internet.

Pros:

• The software works on any internet browser and any operating system or platform.
• It is free to download and use, but paid enterprise support is available.
• .NET language for more powerful add-ons.
• Perfect for layman testers to proficient testers.

Cons:

• High cost.

25. Citrus

Citrus is an automated testing tool with messaging protocols and data formats. HTTP, REST, JMS, and SOAP can all be tested within Citrus. It can help you automate integration tests for virtually any messaging protocol or data format. It provides robust validation mechanisms for XML message contents and allows one to build complex testing logic.

Pros:

• Citrus reliably helps you achieve your quality, function, and stability goals.
• It has great documentation.
• Trouble-free migration from development to production.

26. Dredd

Dredd is a CLI tool for testing APIs and their documentation. It lets you run ad-hoc tests by using the name of the API documentation and the URL of the API. Dredd reads the API documentation and validates all the responses as they are written in the documentation. Hence, it not only confirms the validity of the documentation but also tests the API as per the documentation. It supports multiple languages like PHP, Node.js, Python, Rust, Ruby, Perl, and Go.

Pros:

• Very easy to use and supports multiple programming languages.
• It validates API as well as API documentation.
• It also supports Hooks.

27. HTTP Toolkit

HTTP Toolkit lets you easily mock HTTP(S) calls — super helpful for debugging, testing, and quick API prototyping. HTTP Toolkit is completely open-source and free to download for Windows, Linux & Mac.

28. API Tester

API Tester is unique in that it offers a mobile app to test any API. The service offers guides for interacting with popular APIs, such as GitHub’s GraphQL API, Google Cloud APIs, YouTube API, Twitter API, and others.

Final Thoughts

This article covered the best 25 tools for testing REST, SOAP, or HTTP APIs. You can test web API functionalities and avoid errors with any of these top testing services.

Virtually all of the API test tools listed above work well and are great options. Yet, keep in mind, it all depends on personal experience. These were my favorite API tools, but your list could be much different. There is no one perfect tool for everyone, and every organization has varying requirements.

Apart from these 25, there are many other API testing options. Did we leave out an API testing tool? Please comment below, and we’ll consider adding it to our list!