Top 10 Best API Testing Tools

The API testing tools are software programs that assist developers and testers in examining the functionality of their API programs. These tools simplify Quicken and simplify testing. It is of paramount importance to have the appropriate testing tools, whether you are developing a mobile-based application, a Web-based application, or any other type of software that is based on APIs.

In this article, we will discuss the top API testing tools as of 2025. We will consider why they are special, how they can be used, and which of them can suit your needs best. Starting from a novice developer or an expert developer, this guide will make you discover all about API testing tools in a clear, easy-to-understand language.

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What Are the Best API Testing Tools?

The top-rated tools that can be used to perform API testing are software applications that can aid in testing, monitoring, a nd ensuring that your APIs are properly working. Consider them as quality assurers of your APIs. They request your API, verify the answer, and inform you whether everything is okay.

Such tools can test various things, such as:

• Does the API respond quickly?
• Is the data correct?
• Is the API able to support a large number of users?
• Do you have any security issues?

This whole process could be easily automated and made easier using the best api testing tools. Most of the work is done by these tools as opposed to manually testing everything (which is time-consuming to do). Instead, they are able to execute hundreds and thousands of tests in a few minutes and provide you with detailed reports about what is and is not working.

Benefits of Using Best API Testing Tools

With the most appropriate api testing tools, you receive numerous benefits:

• Faster Development Speed: Automated testing and validation are essential as they help teams deliver products faster.
• Better API Performance: Testing is done to confirm that APIs will react quickly in all cases of load.
• Fewer Bugs in Production: Early detection of errors implies that actual users have fewer problems.
• Easy Documentation: Good will automatically generate documentation of your API tests.
• Confidence in Updates: Re-test after modification to make sure that nothing goes off.

Top 10 Best API Testing Tools

1. Postman

Postman is among the best and widely used in the world best api testing tools. It began as a simple Chrome extension, but has evolved into an API testing platform that is strong and full-fledged. Millions of developers love Postman due to its simple-to-use nature and beautiful, clean interface. Postman can be used to test REST, SOAP, and GraphQL APIs. It is compatible with Windows, Mac, and Linux.

Key Features

• A visual interface that is easy to use for making tests.
• Collection and script-based automated testing.
• Teamwork and joint working area.

Pros

• Easy-to-use interface and design.
• Free version with superior functions.
• Large community for support

Cons

• Slow when handling big projects.
• Paid plans are needed to have advanced features.
• Complex scenarios learning curve.

Best For

Beginners

Pricing

Free plan available; Paid plans start at $12/month

Website: https://www.postman.com

2. SoapUI

One of the best products in API testing is SoapUI, which is specifically used to test SOAP and REST APIs. SoapUI was developed by SmartBear and has been in existence for a long period of time. And has been trusted by thousands of companies all over the world. It is a potent tool that can cope with complicated testing conditions. SoapUI is available in two platforms, including SoapUI Open Source (free) and SoapUI Pro (paid).

Key Features

• SOAP and REST API testing.
• Vulnerability finding, Security testing.
• Load testing features were provided.

Pros

• Stunning advanced testing capabilities.
• Free version available as open-source.
• Multi-dimensional testing within a single tool.

Cons

• Difficult interface for new users.
• Technical knowledge is needed to use it.
• It can be resource-intensive on the computers.

Best For

Professionals

Pricing

Free open-source version; Pro version starts at $659/year

Website: https://www.soapui.org

3. Rest-Assured

One of the Popular API testing tools in 2025 that will be used by Java developers is Rest-Assured. It is a Java library that simplifies testing of REST APIs to an extremely easy task. Rest-Assured is also open-source and free of charge. The thing is that you write tests with the help of very natural and English-like language a,, nd it is easy to understand. An example would be to write something such as “given.when.then” that reads almost like a sentence.

Key Features

• Java-based testing library
• Readable syntax, such as plain English.
• Java testing: integration with JUnit/TestNG.

Pros

• Free and open-source forever
• Java developers find it easy to learn.
• BIG pipelines are great for automation.

Cons

• Java programming skills are necessary.
• Poor interface GUI selections.
• Non-programmers are not suitable.

Best For

Developers

Pricing

Completely free (open-source)

Website: https://rest-assured.io

4. JMeter

A demonstration of the power of a Free API testing tool is Apache JMeter, which is enormously powerful in terms of performance and load testing. JMeter was originally built as the tester of web applications, but has since developed into an overall testing tool, capable of testing APIs, databases, and a variety of other protocols. It is free and is maintained by the Apache Software Foundation. JMeter can load your API with hundreds or thousands of users simultaneously, to determine how your API will behave when it is under heavy load.

Key Features

• Thousands of user load testing.
• Monitoring of performance and reports.
• Various protocol support is provided.

Pros

• Wholly free open-source tool.
• Available powerful load testing capabilities.
• On-the-job community support.

Cons

• Learning curve is steep for new users.
• The interface is old-fashioned and complicated.
• On testing machines, intensive on resources.

Best For

Performance

Pricing

Free (open-source)

Website: https://jmeter.apache.org

5. Katalon Studio

Katalon Studio is the best API testing tool that integrates API testing with both web testing and mobile testing. The tool is ideal for a team that requires testing various kinds of applications. Katalon employs a codeless method, which implies that you can build tests without writing any code with the help of its graphical interface. It does, however, also allow scripting to allow more control to advanced users. Katalon Studio is easily integrated with other popular tools such as Jira, Git, and Jenkins, which allows them to easily integrate into your current workflow.

Key Features

• Codeless setup of tests.
• Combined API and web, mobile testing.
• Connection with well-known tools.

Pros

• No coding required to start
• All-in-one testing solution
• Free version available now

Cons

• It can be slow sometimes
• Reduced personalization on the free version.
• Support is only available in paid plans

Best For

Teams

Pricing

Free version available; Paid plans start at $167/month

Website: https://www.katalon.com

6. Insomnia

Among the more beautiful and modern interfaces and the simplicity of Popular API testing tools in 2025, there is insomnia. It is meant to be as easy as possible to debug and test the API. Insomnia has a high level of versatility as it supports REST, GraphQL, and gRPC APIs. The tool is developer-centered, and it includes environment variables, code development, and the ability to add a new plugin. Insomnia is ideal in cases where developers wish to have a distraction-free interface to test their APIs.

Key Features

• Attractive, spotless interface design.
• GraphQL and REST support
• Extension system Plugin system.

Pros

• Simple and intuitive to use
• Rapid and speedy implementation.
• Great for GraphQL testing

Cons

• Fewer features than the rivals.
• Free collaboration between teams Limited.
• Less community than Postman.

Best For

Developers

Pricing

Free core version; Paid plans start at $5/month

Website: https://insomnia.rest

7. Paw (RapidAPI for Mac)

Paw, which is currently RapidAPI, is among the Paid API testing software that are only compatible with Mac. Paw provides one of the most enjoyable API testing experiences in case you are using a Mac computer. The application has a natural interface with Mac that is easy to use. Paw can produce code in more than 20 programming languages, which makes it incredibly helpful in the face of developer who require the APIs to be integrated into their applications. It can support any form of APIs, such as REST, GraphQL, and SOAP.

Key Features

• Optimized native Mac application.
• Generation of all 20+ languages.
• Values and variables are dynamic.

Pros

• Beautiful Mac-native design
• The ability to generate powerful code.
• Great performance on Mac

Cons

• Mac only – no Windows
• Costly as an alternative.
• Smaller user base overall

Best For

Mac

Pricing

Starts at $49.99 (one-time purchase)

Website: https://paw.cloud

8. Karate DSL

One of the Free API testing tools which are gaining popularity rapidly is Karate DSL. It is an open-source tool that incorporates API testing service, mocks, performance testing, a nd even automation of the UI within a single framework. The special thing about Karate is that the tests are written using a simple language, which a non-programmer can read and comprehend. There is no need to be a coder to write tests in Karate. The tool is written in a syntax derived from a BDD (Behavior Driven Development) syntax that is written as plain English.

Key Features

• Simple, readable test syntax
• A combination of API testing and mocks.
• Native HTML reports were provided.

Pros

• Completely free open-source
• Easy to learn for everyone
• Extensive functionality in-built.

Cons

• Documentations are cumbersome.
• Community is less than alternatives.
• The process of debugging may be complicated.

Best For

Automation

Pricing

Free (open-source)

Website: https://karatelabs.github.io/karate

9. Swagger (OpenAPI)

Open API (Swagger) is among the best API testing tools used to design and test APIs. It is, in fact, a collection of tools that collaborate. Swagger UI allows you to explore and manipulate your API in your browser. Swagger Editor enables you to create the API with the help of the OpenAPI specification. Though Swagger is commonly regarded as a documentation tool, it also works well as a tester. Any API calls can be made in the Swagger UI interface without any code being written.

Key Features

• Combined API design and testing.
• Automatically generated interactive documentation.
• Open API specification standard support.

Pros

• Free and open-source forever
• Excellent in documentation development.
• Specification of the industry standard applied.

Cons

• Increased basic testing features.
• Supports Open API specification file.
• Not a dedicated testing tool

Best For

Documentation

Pricing

Free (open-source); Commercial tools available

Website: https://swagger.io

10. Testfully

Testually is a relatively new best api testing tool that is developing popularity among developers. It is a simple, cloud-based API testing tool that is collaboration-oriented. Testually has a very beautiful interface, which is easy to use, even for non-technical ones. The tool has support for REST and GraphQL APIs, and it has the following features: environment variables, assertions, and test collections. The peculiar feature of Testfully is the use of teamwork and the sharing of workspaces and real-time updates.

Key Features

• Testing platform in the clouds.
• Live teamwork functionality.
• In-built performance testing.

Pros

• Clean interface design, Modern.
• Good free plan available
• Quick and prompt application.

Cons

• Relatively new tool
• Smaller community at present.
• Restricted integrations on offer.

Best For

Startups

Pricing

Free plan available; Paid plans start at $10/month

Website: https://testfully.io

Future of Best API Testing Tools

The most appropriate api testing tools are dynamic. Here’s what’s coming:

• AI-Powered Testing: In the near future, artificial intelligence will develop and process tests automatically.
• Better Cloud Integration: Additional tools will be transferred fully to the cloud-based testing solutions.
• Improved Security Testing: All testing tools will be characterized by security features.
• Low-Code/No-Code Testing: The increased number of tools will allow non-programmers to build complex test situations.
• Real-Time Collaboration: Collaborative work will be conducted on such tests as Google Docs.

Conclusion

Both Free API testing tools, such as Rest-Assured and JMeter, and Paid API testing tools, such as Paw and Katalon Studio Pr, are available. The Top API testing tools, such as Postman and SoapUI, have been proven over the years of working, whereas Popular API testing tools in 2025, such as Insomnia and Testfully, are becoming more popular with their modern practices.

Also, it is essential to remember that the tool you will use will be best depending on your needs, budget, technical expertise, and the number of people on your team. There is nothing to be afraid of when it comes to experimenting with various tools. The majority of the best API testing tools have a free version or free trial so that you can give them a test run.

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FAQs

Q1: What is API testing, a nd the significance of this testing?

API testing is used to ensure that your API is functioning as expected, fast, and error-free. It matters because APIs link the various components of modern software, and broken APIs imply broken software.

Q2: Are there any free tools that I can use to test API professionally?

Yes! Several professional teams consider free tools such as Postman, JMeter, and Rest-Assured to be taken seriously. Most of the testing situations can be performed with free tools since they have all the required features.

Q3: Do I require the use of coding skills to use API testing tools?

Not always. There are visual APIs in tools such as Postman, Katalon Studio, and Insomnia, and in these tools, you can interact with APIs without any code. Nonetheless, there are more sophisticated features that may need simple coding.

Q4: What is the number of API tests that I should do?

This will be determined by the complexity of your API. Begin with simple tests of all of your API endpoints, followed by tests of error conditions, security, and performance. The goal should be to get at least 70-80% test coverage.

Q5: Do API testing tools have the capability of testing mobile app APIs?

Yes! All of the best API testing tools discussed in this paper are capable of testing any API regardless of whether it is used by a web app, mobile apps, or other software. It does not matter what type of API it is, but only the protocol (REST, SOAP, etc.).