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With so many different API testing tools available, figuring out which is right for you is tough. You know you want to determine if your APIs meet expectations for functionality, reliability, security, and performance but need to figure out which tool is best. I've got you! In this post I'll help make your choice easy, sharing my personal experiences using dozens of different API testing software with a variety of projects, with my picks of the best API testing tools.

What Are API Testing Tools?

API testing tools are software used for testing the functionality, performance, security, and reliability of Application Programming Interfaces (APIs). They automate the process of sending requests to an API, receiving responses, and then analyzing them to verify correct behavior and performance under various conditions. These tools are essential in ensuring that APIs, which enable different software systems to communicate, are working as intended.

The benefits and uses of API testing tools include the early detection and resolution of issues with APIs, leading to more reliable and secure software applications. They save time and increase efficiency by automating repetitive testing tasks. By thoroughly testing APIs, these tools help maintain seamless communication between different software systems, ensuring data is accurately exchanged and processes are executed correctly. They are vital in today's interconnected software environment, where APIs play a crucial role in the integration of diverse systems and services.

Overview Of The 10 Best API Testing Tools

Here I’ll go over each tool’s use case, summary, and features and provide screenshots for a glimpse into the user interface.

1

Katalon Studio

Best for running API test automation across multiple environments

This is an aggregated rating for this tool including ratings from Crozdesk users and ratings from other sites.
4.4
46 reviews

Freemium plan

From $25/month

Katalon Studio equips DevOps and testing teams with several features to ensure they have a robust strategy to produce well-tested applications.

It is immensely flexible, allowing you to run tests on all platforms, whether desktop, web, or mobile. It can be used on various OSs like Linux, macOS, and Microsoft Windows. Katalon also permits you to run automated tests on UI elements such as pop-ups, iFrames, overlays, and so on.

One of Katalon Studio’s selling points is that it allows you to create and reuse automated scripts without going through the arduous process of writing code. While this codeless experience is a boon for beginners, it also provides sophisticated extensions and plugins for experts.

Moreover, Katalon gives you out-of-the-box, ready-made seamless integration with DevOps pipelines and CI testing tools. These factors help to drastically reduce the time necessary to create automated scripts.

It also provides several ways to customize and enhance your test procedure to fit your application’s context. These include keyword-driven testing, page object model testing, data-driven testing, and TDD/BDD Testing.

It provides support for the command line and other execution environments. It also supports Groovy, a language that is Java domain syntax compatible.

Katalon Studios comes with a free version but it doesn’t provide support for API monitoring in any of its products. Moreover, its paid plans are prohibitively priced, with Runtime Engine and Studio Enterprise costing $1,499 USD per license/year and $1,899 USD per license/year respectively.

2

Sauce Labs

Automated API test generation for fast debugging on cross-browser and mobile apps

This is an aggregated rating for this tool including ratings from Crozdesk users and ratings from other sites.
4.3
131 reviews

28 Days Free Trial

From $50/month

Sauce Labs is a comprehensive continuous testing cloud for web and mobile applications that allows you to complete both manual and automated testing through a variety of testing channels. The tool provides a real device cloud so you can test across multiple devices. Sauce Labs also offers enterprise security and a proprietary data center.

Sauce Labs offers a variety of automated and manual testing methods, ensuring full test coverage of your applications. The tool provides a cross browser testing feature, which allows you to test end-to-end on various browsers. Sauce Labs also offers the ability to complete automated mobile testing so you can write tests for various devices to ensure your application runs smoothly.

Sauce Labs offers integrations with platforms such as Github, Jenkins and Bamboo, as well as chat applications such as Slack.

The cost of Sauce Labs starts at $39/month for the Live Testing package. The tool also offers a 28-day free trial.

3

SmartBear

Best continuous testing platform for DevOps

This is an aggregated rating for this tool including ratings from Crozdesk users and ratings from other sites.
2
1 review

30-day free trial

Prices vary by product

Smartbear is a simple, yet scalable GUI test automation tool that focuses on desktop, web, and mobile testing. These modules allow you to recreate repeatable tests easily across various platforms, environments, and multiple devices.

Smartbear’s TestComplete feature offers automated UI Testing works across a diverse range of desktop applications, whether they’re built on Windows, or designed with WPF, Java, .Net, or other software languages. It makes continuous testing a breeze by enhancing your ability to run automated tests with test scripts, along with providing record and replay capabilities.

Smartbear’s Cross Browser Testing provides an all-in-one web testing platform for cross-browser compatibility. So, when it comes to web applications, Smartbear allows you to design reusable tests and run parallel execution tests for several platform browser configurations like chrome, including JavaScript frameworks like Angular and React.

Its ReadyAPI solution allows test engineers to accelerate API quality through web services like GraphQL, RESTful, and SOAP.

To add to its strong suite of test products, Smartbear acquired the open-source Cucumber, thereby merging the latter’s leadership in a behavior-driven development (BDD), especially among agile teams, with its expertise in test automation.

Smartbear’s TestComplete and ReadyAPI modules are expensive.

TestComplete Base offers Desktop, Mobile, and Web options; and it allows users to mix and match these according to their needs and affordability. Choosing the Desktop option alone starts at $5,438 USD. Mobile alone costs $6,158 USD, while the Web option by itself starts at $5,438 USD.

4

Postman

Best for streamlining the API lifecycle

$12, $29, and $99 respectively; all are charged in USD per user/month but billed annually

Postman’s abundant resources make it easy to build, test, and debug APIs together. It allows QA and DevOp teams to stay committed to favorable short release cycles in the spirit of Agile methodology and continuous testing/integration.

Postman provides templates for testers to easily create test suites by reducing the amount of time spent on coding test scripts. Its schema editor makes it possible to work with files of various sizes and formats.

Equipped with an API client that automatically detects the contents of an HTTP response body – from its format, language, and links, Postman provides a streamed and effective environment to work and accelerate API test and development.

In addition to supporting all HTTP methods, it is also possible to define complex API requests for Websockets, GraphQL, OpenAPI, and SOAP formats.

Although Postman’s vast structure can be a challenge to implement for beginners, it more than makes up for this in several ways. It saves work progress by automatically storing all your API calls in your cloud-based system. Hence, you can easily reuse them to quickly create a prototype API workflow.

In addition to all these benefits, Postman is incredibly affordable. It comes with a free version that allows you to do run-of-the-mill stuff like designing and testing APIs. Postman’s other pricing tiers are Basic, Professional, and Enterprise. These are priced at $12, $29, and $99 respectively; all are charged in USD per user/month but billed annually. However, the prices are higher when billed monthly.

5

Apache JMeter

Ideal for testing performance both on static and dynamic resources

Free to use

Apache JMeter is a desktop application that allows you to measure test performance of applications across browsers and mobile OSs. The tool focuses on loading testing and provides an intuitive user interface. Apache JMeter is also capable of carrying out other testing types such as functional testing.

Apache JMeter can turn on/off variables depending on your target testing environment, which allows you to configure your test cases easily. The tool allows you to identify the issues in your performance by scaling your tests and rerunning existing scripts.

Apache JMeter also allows you to run stress tests so you are able to find breaking points in your systems, ensuring their reliability.

Apache JMeter is fully open source and free to use.

6

Apigee Edge

Best for building, managing, and testing API proxies

Apigee Edge allows developers to test API proxies with ease. Apigee Edge enables API architects to build these API proxies – gateways or intermediaries so programmers can rapidly develop business solutions.

It provides robust API management functionality by wrapping your API with a proxy layer. If your application lacks an Apigee, it means its API is called directly by other APIs that want to consume its services.

Therefore, Apigee Edge provides developers with several abstractions and mechanisms so they don’t have to consume the services they need directly. This provides great security implementations for APIs, so you can share services without exposing your code.

In addition to scaling and analyzing your API, Apigee Edge also provides API authentication and monetization.

Apigee Edge provides users with the flexibility of not having to use any domain-specific language but extracting response data with either XML or JSON.

Apigee’s Evaluation plan is free. For its paid plans, customized pricing is available upon request.

7

Parasoft SOAtest

One-stop API testing solution for DevOps

Parasoft provides software engineers and DevOps with a comprehensive suite of software testing and QA platforms. It provides a range of solutions, starting from software development to testing automation that is powered by artificial intelligence.

Parasoft SOAtest simplifies the complexity of testing through visual drag-and-drop mechanisms to facilitate scriptless API Testing without writing a single line of code. It covers testing needs ranging from unit testing to functional and load testing across APIs and HTTP requests.

Unlike most API testing tools that predominantly handle REST API test cases, the Parasoft SOAtest module takes care of both REST and SOAP web services. In contrast to most automation tools, Parasoft allows you to integrate C/C++ tests into your software development environment through an IDE, in addition to containerized deployments, and CI/CD pipelines like Jenkins.

Overall, Parasoft SOAtest makes it easier to automatically enforce industry compliance, especially by its ability to early detect defects. As its name suggests, Parasoft Virtualize provides API virtualization that provides DevOps with deep insights through informative diagrams, detailed reports, and dashboards.

However, Parasoft is a bit complex to get started with but it more than makes up for that by enabling DevOps teams to implement quality assurance and security across the software development lifecycle.

Parasoft SOAtest doesn’t have any free version or free trial. Pricing is provided upon request.

8

Subject7

Empowering anyone to become a test expert through codeless automation

$250/user/month

Subject7 makes becoming an automation expert accessible to anyone through its codeless automation. Thereby, leveling the playing field when it comes to API testing.

It is an exceptional automation tool for both technical and non-technical users in addition to reducing maintenance for QA engineers and testers. You can create easily create robust test flows with widget definitions, AJAX calls, and configuration templates across a library of over 100 hundred platforms, android, and iOS devices.

Whether it’s web or native app testing, Subject7 simplifies the process by enabling test authoring and running of sophisticated API automation tests a breeze. It incorporates a wide range of end-to-end test capabilities that encompass desktop, web applications, web services, mobile, security, load testing, and much more.

Subject7 is capable of delivering robust testing capabilities that scale adequately while providing enterprise-grade security, whether it’s on-premises or in the cloud.

The adaptability of Subject7 lies in its ability to provide GUI interfaces to interact with a wide range of automated commands, at a minimum, eliminating the need to write java codes. In addition, it provides several in-built commands to perform interactions for web and desktop applications.

It uses both open APIs and native to seamlessly facilitate integration with existing Agile tooling and DevOps ecosystems.

Unfortunately, Subject7 doesn’t provide any free version or free trials for users to test out its features before deciding to make a purchase. Its Professional plan is reasonably priced, although it requires an annual subscription of $250 USD per user/month. Both its Enterprise and Private Cloud plans provide customized pricing upon request.

9

Hoppscotch

The fastest and easiest API builder

Hoppscotch is a free, open-source tool and API request builder. Hoppscotch provides REST API testing via a GUI API client to make HTTP requests and validate API request responses.

Incidentally, it was built as an alternative to Postman. And compared to other API frameworks, Hoppscotch has a more minimalistic, less distracting interface. Hence, Hoppscotch enables you to write test scripts with minimal distraction so requests are created faster.

For instance, Hoppscotch has a feature called Collections, which allows testers to group and save all the HTTP requests belonging to a single API endpoint together in a logical, organized manner.

Hoppscotch is an asset to API development environments because it allows developers to create HTTP requests in a logical, step-by-step manner. Especially when the API contains request objects with many layers of nested arrays and HTML objects.

Along with pre-request scripts, DevOp teams save precious time on their API development efforts. In addition to the REST services it provides, Hoppscoth also incorporates GraphQL to enable developers to retrieve descriptive data queries along with their API tests.

Therefore, Hoppscotch benefits resource-driven apps by ensuring the API is reliable and highly secure.

Hoppscotch is free but it accepts donations through PayPal and Patreon.

10

SoapUI

Widely-used automated testing tool for SOAP and REST APIs

14 Days Trial Periods

From $759/license

SoapUI is an immensely popular API tool offered by SmartBear and includes ReadyAPI and TestEngine in its product suite. However, its popularity stems from the open-source technology at its core and its array of advanced tools.

One of the main factors driving its popularity is the fact that it both supports REST services and SOAP APIs. In addition to these, SoapUI’s ReadyAPI provides end-to-end testing for widely adopted protocols like GraphQL, Java Database Connectivity (JDBC), Java Message Service (JMS), and other APIs.

With TestEngine, SoapUI enables you to run test suites at a tremendous scale and in parallel to accelerate delivery pipelines.

SoapUI is a robust cross-platform solution that allows you to engage in various testing methodologies. It is widely adopted because it covers the whole gamut of the testing spectrum, ranging from functional API testing, load testing, security, and API mocking.

SoapUI comes with a Pro version and a free, open-source version.

ReadyAPI has three modules, namely API Test Module, API Performance Module, and API Virtualization priced at $759 USD per license, $5,639 USD per license, and $1,060 USD per license respectively. They are billed annually and provide 14-day trial periods.

Preview Image - <h2 class="c-block__title b-summary-table__title c-listicle__title h3" > Compare Software Specs Side by Side</h2>

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Other API Testing Tools

Here are a few more that didn’t make the top list.

  1. Tricentis Testim

    AI-powered automation for quick, scalable test solutions

  2. QA Wolf

    Best for outsourcing test creation, maintenance, and issue reports to a team of QA experts

  3. Reflect

    Perform API testing in tandem with UI tests for an all-in-one approach

  4. SmartBear ReadyAPI

    Best easy-to-use, no-code API testing tool for your continuous delivery pipeline

  5. Rest Assured

    No code API test solution built for everyone

  6. Tricentis

    API test validation tool for Java RESTful services.

  7. Karate DSL

    The only open-source tool to combine API test automation, performance, and UI automation.

Best API Testing Tools: Comparison Criteria

This is the evaluation criteria I used in making my API automation testing tools selection:

  1. User Interface (UI): Is the layout clean and inviting? Does it have well-designed navigation elements that flow naturally from one related task or menu to the other? A hallmark of a good user interface is the ability to highlight important tasks in their immediate context without being obtrusive.
  2. Usability: API testing teams need to hit the ground running. They shouldn’t spend an inordinate amount of time figuring out how an automation tool works. So, I evaluated the level of difficulty required to learn, master, and use an automation tool.
  3. Integrations: DevOp and QA teams utilize myriad tools, so it’s crucial the API testing solution they choose can communicate and integrate easily with other tools they’re already using. I looked at how the API testing tool seamlessly integrates with other CI or deployment pipeline elements.
  4. Value for $: Here, I looked at how competitive a tool’s pricing rates are compared to others. An extraordinary testing tool should provide value for money to the customer over and beyond its price tag.

API Testing Solutions: Key Features

Test automation

Test automation is no longer a “nice-to-have” luxury. Continuous testing has made test automation an indispensable,  “must-have” feature in modern automation tools.

API tools that incorporate a high degree of test automation eliminate the need for constant human monitoring, while minimizing the incidence of human error.

In addition, the bar is being raised for automation testing as most tools are currently equipped with AI capabilities to detect anomalies and other hidden patterns.

CI/CD Integration

DevOps teams have embraced the Agile methodology and the principle of continuous integration to constantly deploy software through the application pipeline. To keep up with this software development paradigm, API testing tools should be capable of integrating seamlessly with these CI/CD workflows and pipelines.

Reliable test coverage

An API testing tool should be robust, flexible, and expansive enough to accommodate a broad range of test coverages. It should allow QA teams to build test suits for both the functional requirements of an app, in addition to performing non-functional tests for security, performance, and usability.

Its reliability should inspire testers to trust their automatic testing units and test suites in general. While the scope of test coverage is determined by the tester, a good API testing tool should be systematic in facilitating test effectiveness and completeness.

Optimized workflows

A good API test tool should make it easy to implement and execute its workflows by supporting a wide breadth of testing environments, operating systems, scripted languages, and web browsers.

Relevant API FAQs

Have a few lingering questions? Start here!

What do you think about this list?

So, these are my top picks for the best API testing tools. There are many API automation tools that do a very good job in the API testing domain. As a result, it was difficult filtering them down to the cream of the crop. 

I would like to hear your opinion on the lists, including thoughts on any tool you think should have made the cut, and where the list might be improved.  

In the meantime, please check out a related article on the 10 Latest Software Testing Tools QAS are Using

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By Eze Onukwube

Eze has a master's degree in communications with over 10 years of experience as a software engineer. His playground is at the intersection of technology, process improvement, and simplifying IT concepts.