25 Best API Testing Tools for Building Functional, Secure Applications in 2024

With the increasing need for resilient and secure applications, API testing tools have become essential for maintaining the functional reliability and security of software systems.

In this article, we’ll walk through 25 of the leading API testing tools in 2023. These tools provide an extensive array of features, support for various programming languages, and robust security capabilities, making them indispensable resources for developers and testers alike.

Whether you are a seasoned developer or a QA enthusiast, discover the tools that can streamline your testing processes and contribute to the creation of resilient, high-performance applications.

1. Postman

Postman stands out for its user-friendly interface, making it easy to create and manage API tests. Its extensive testing capabilities, including request generation and response validation, provide comprehensive coverage for API testing. Additionally, its collaboration features facilitate seamless teamwork among developers and testers.

Best for: Postman is an excellent choice for developers and testers who want a powerful yet intuitive tool for API testing. Its robust ecosystem supports a wide range of tasks, including building and automating tests, generating documentation, and simulating endpoints.

Pro tip: Utilize Postman's collections and environments to organize and streamline your API testing process. Collections allow you to group related requests, while environments enable you to manage different configurations, making your testing workflow more efficient.

Postman’s pricing plans include a free version with limited features, paid plans for individual teams ($12/user/month) and businesses ($24/user/month), and an enterprise option.

2. SoapUI

SoapUI is a well-known open-source tool that specializes in testing SOAP and REST APIs. Its extensive feature set, including test generation and assertion capabilities, ensures comprehensive API testing coverage. The integration with other tools enhances its versatility.

Best for: SoapUI is best suited for developers and testers working with SOAP-based APIs or REST APIs. Its powerful features and extensive support make it an ideal choice for organizations relying heavily on these types of APIs.

Pro tip: Use SoapUI's assertion capabilities to validate API responses against expected results, ensuring the accuracy and reliability of your API tests.

ReadyAPI pricing starts at $644 for a one-year license.

3. JUnit

JUnit is a widely used testing framework for Java applications, including API testing. Its simplicity and robustness make it a popular choice among developers. With JUnit, you can easily create automated tests, perform assertions, and generate comprehensive reports.

Best for: JUnit is an excellent choice for Java developers who want a lightweight yet powerful tool for API testing. Its seamless integration with Java projects and IDEs makes it highly convenient to incorporate into existing workflows.

Pro Tip: Leverage JUnit‘s annotations, such as @Test and @Before, to organize and execute API tests efficiently. Additionally, utilize JUnit’s reporting capabilities to obtain detailed insights into test results.

4. REST Assured

RestAssured simplifies API testing for Java projects. Its domain-specific language (DSL) allows for concise and readable code, making API testing a breeze. With RestAssured, you can effortlessly build requests, validate responses, and perform assertions.

Best for: RestAssured is best suited for Java developers who work extensively with RESTful APIs. Its simplicity and expressive syntax make it an excellent choice for writing concise and effective API tests.

Pro tip: Take advantage of RestAssured's built-in support for JSON and XML parsing to extract specific values from API responses. This enables you to perform more granular assertions and validations.

5. Karate DSL

Karate is an open-source framework that combines API testing, mock server, and performance testing capabilities. Its easy-to-read syntax and built-in assertions simplify the process of creating and executing comprehensive API tests. The inclusion of mock server and performance testing features further enhances its versatility.

Best for: Karate is suitable for developers and testers who prefer a single tool to handle API testing, mock server creation, and performance testing. Its simplicity and comprehensive feature set make it a valuable asset for teams focusing on API development and testing.

Pro tip: Leverage Karate's scenario outline feature to execute tests with multiple test data inputs, allowing for efficient testing of various scenarios without duplicating code.

6. Newman

Newman, a command-line tool that integrates with Postman, enables automated API testing. It is ideal for incorporating API tests into continuous integration and delivery pipelines. Newman allows you to run Postman collections in a CI/CD environment, ensuring consistent and reliable testing.

Best for: Newman is a valuable tool for teams that rely on Postman for API testing and want to automate their testing process. It streamlines the execution of Postman collections, making it convenient for integrating API tests into the CI/CD workflow.

Pro tip: Integrate Newman with your preferred CI/CD tool to automate the execution of Postman collections as part of your deployment pipeline. This ensures that API tests are consistently executed, providing early detection of issues in your APIs.

7. Apache JMeter

Apache JMeter is a powerful tool primarily used for load and performance testing. However, it also offers excellent support for API testing. Its ability to simulate various scenarios and measure API performance under different loads provides valuable insights for ensuring API functionality and scalability.

Best for: Apache JMeter is best suited for organizations that require not only API testing but also load and performance testing capabilities. It caters to developers and testers who want a comprehensive tool for testing the performance and reliability of their APIs.

Pro tip: Combine Apache JMeter‘s API testing capabilities with load and performance testing to gain a holistic view of your API’s behavior under different load conditions. This helps identify bottlenecks and ensure your API can handle expected traffic levels.

8. TestComplete

TestComplete is a comprehensive testing platform that supports API testing, along with UI and load testing. Its script-free interface and extensive functionality make it suitable for both beginners and experienced testers. With TestComplete, you can create automated API tests without the need for coding.

Best for: TestComplete is a versatile tool for organizations that require not only API testing but also UI and load testing capabilities. It caters to testers who prefer a script-free approach and want a unified testing platform.

Pro tip: Utilize TestComplete's data-driven testing capabilities to efficiently test your APIs with different test data sets. This enables you to cover a wide range of scenarios and ensure the robustness of your API implementation.

9. Selenium WebDriver

While primarily known for web UI testing, Selenium WebDriver can also be used for API testing. Its flexibility, support for multiple programming languages, and vast community make it a valuable tool for testing web-based APIs. With Selenium WebDriver, you can leverage your existing Selenium knowledge to extend your testing capabilities to API testing.

Best for: Selenium WebDriver is an excellent choice for organizations that already use Selenium for web UI testing and want to expand their testing scope to include API testing. Its compatibility with multiple programming languages makes it versatile for teams with diverse technology stacks.

Pro Tip: Use Selenium WebDriver's HTTP client libraries, such as HttpClient or RestAssured, to make API requests directly within your Selenium tests. This allows you to seamlessly incorporate API testing alongside your web UI tests.

10. Katalon Studio

Katalon Studio is a powerful automation testing tool that supports API testing. Its built-in features, such as record and playback, data-driven testing, and reporting, make it an excellent choice for creating functional and secure API tests. Katalon Studio provides a comprehensive platform for both API and UI testing, facilitating streamlined test automation.

Best for: Katalon Studio is suitable for organizations that require a single tool for API and UI testing. It is particularly beneficial for teams that prioritize efficient test creation, execution, and reporting.

Pro tip: Utilize Katalon Studio's record and playback feature for API testing to quickly generate test scripts by capturing interactions with APIs. This reduces the time and effort required to create API tests, especially for testers with limited coding experience.

11. PyTest

PyTest is a Python testing framework that offers intuitive syntax and powerful assertion capabilities. Its plugin architecture and support for API testing empower developers to build reliable and scalable tests effortlessly. PyTest's simplicity and flexibility make it a preferred choice for Python developers.

Best for: PyTest is ideal for Python developers who value simplicity and prefer a lightweight testing framework.

12. Cucumber

Cucumber's behavior-driven development (BDD) approach fosters collaboration between developers, testers, and stakeholders, leading to better communication and understanding of API requirements. Its plain-text executable specifications make it easy to create and maintain test scenarios, even for non-technical team members.

Best for: Cucumber is ideal for organizations that prioritize clear and concise test documentation and collaborative test development. It is well-suited for projects with cross-functional teams and complex API requirements.

Pro tip: Use Cucumber's tagging feature to organize and execute specific sets of API tests, allowing for targeted testing based on different criteria, such as functional areas or release cycles.

13. Supertest

Supertest's lightweight and expressive syntax makes it a developer-friendly tool for testing Node.js HTTP servers and APIs. It seamlessly integrates with popular testing frameworks like Mocha and Jest, enhancing its flexibility and ease of use.

Best for: Supertest is perfect for Node.js developers who want a simple yet effective library for testing their HTTP servers and APIs. Its minimal setup and integration capabilities make it a valuable asset for Node.js projects.

Pro tip: Leverage Supertest's chaining and assertion methods to create concise and readable API test scripts, enhancing code maintainability and clarity.

14. Apigee

Apigee's comprehensive API platform covers all aspects of API development, including testing. It offers a powerful set of tools for designing, building, testing, and monitoring APIs, streamlining the API development lifecycle.

Best for: Apigee is best suited for organizations that require a robust and all-encompassing API platform. It caters to developers and testers who need a single platform for API testing, management, and monitoring.

Pro Tip: Use Apigee's traffic simulation features to test API behavior under different traffic loads, ensuring that your APIs perform optimally under real-world conditions.

15. Dredd

Dredd's focus on validating API blueprints against actual implementations ensures that the implemented APIs adhere to their documented specifications accurately. Its command-line interface allows for seamless integration into CI/CD pipelines.

Best for: Dredd is ideal for organizations that prioritize strict adherence to API documentation specifications. It caters to developers and testers who want to ensure consistency between API blueprints and actual API implementations.

Pro tip: Set up Dredd as part of your continuous integration process to automatically validate API blueprints against your APIs with every code change, ensuring that documentation and implementation remain in sync.

16. Assertible

Assertible provides an intuitive interface for creating, running, and managing API tests. Its real-time monitoring and error detection features allow for quick identification of API issues, improving the reliability of your applications.

Best for: Assertible is a great choice for organizations that need a user-friendly tool for API testing and monitoring. It caters to developers and testers who want to detect and resolve API errors promptly.

Pro tip: Utilize Assertible's webhooks and integration capabilities to integrate API testing into your existing CI/CD workflows and collaboration tools, ensuring a seamless testing process.

17. HTTPie

HTTPie's human-friendly command-line interface simplifies the process of making API requests. Its support for session persistence and built-in JSON support enhances the efficiency of testing and debugging APIs.

Best for: HTTPie is well-suited for developers who prefer a command-line tool for making API requests without the complexity of using cURL or other HTTP clients. Its simple syntax makes it beginner-friendly as well.

Pro tip: Use HTTPie's syntax highlighting feature to quickly identify and troubleshoot potential issues in API requests and responses, enhancing the efficiency of your testing workflow.

18. WireMock

WireMock's flexible mock server capabilities enable developers to simulate various responses and scenarios, ensuring comprehensive testing of API integrations and dependencies. Its ease of use and lightweight nature make it a developer-friendly tool.

Best for: WireMock is perfect for developers who need a simple and versatile mock server for testing APIs without the need for extensive configuration.

Pro tip: Utilize WireMock's recording feature to capture and generate mock responses based on real API traffic, saving time and effort in creating accurate mock data for testing.

19. Paw

Paw's full-featured HTTP client provides developers with a powerful toolset for building and testing APIs on macOS. Its intuitive interface and support for dynamic environments and authentication make it a go-to choice for macOS users.

Best for: Paw is an excellent choice for macOS developers who require a feature-rich HTTP client with API testing capabilities. Its user-friendly design and extensive feature set enhance the productivity of API testing workflows.

Pro Tip: Create dynamic environments in Paw to manage different configurations and authentication settings for your API tests, enabling efficient testing across various environments.

20. Insomnia

Insomnia's cross-platform compatibility, visually appealing interface, and support for various authentication methods make it an attractive API testing tool for developers and testers. Its extensive testing capabilities cater to different API scenarios effectively.

Best for: Insomnia is perfect for developers working on multiple platforms who need a feature-rich API testing and design tool. Its appealing interface and ease of use enhance the testing experience.

Pro tip: Leverage Insomnia's environment and variable features to manage test data and configurations efficiently, enabling seamless testing across different environments.

21. Swagger

Swagger UI's automatic generation of interactive API documentation simplifies the exploration and testing of APIs directly from the documentation. Its support for OpenAPI specifications ensures accurate understanding and effective testing.

Best for: Swagger UI is ideal for organizations that prioritize detailed and interactive API documentation and want to facilitate API testing directly from the documentation.

Pro Tip: Customize the Swagger UI appearance to match your brand or project theme, creating a cohesive and professional look for your API documentation and testing interface.

22. Runscope

Runscope's cloud-based platform allows developers to test and validate APIs under real-world conditions. Its traffic recording and replay features enable thorough API testing, ensuring optimal performance and reliability.

Best for: Runscope is a valuable tool for organizations that require cloud-based API testing and monitoring. It caters to developers who want to test APIs under realistic scenarios.

Pro tip: Set up scheduled tests in Runscope to regularly monitor your APIs' performance and detect potential issues proactively.

23. Parasoft SOAtest

Parasoft SOAtest's enterprise-grade capabilities, including functional and security testing, make it a comprehensive solution for API testing. Its service virtualization feature enables developers to test APIs with external dependencies efficiently.

Best for: Parasoft SOAtest is well-suited for organizations that require a robust tool for both functional and security testing of APIs. It caters to developers and testers working with complex API scenarios and integrations.

Pro Tip: Utilize Parasoft SOAtest's security testing features to identify potential vulnerabilities in your APIs and ensure that they meet stringent security standards.

24. Telerik Test Studio

Telerik Test Studio's visual testing approach simplifies the creation of API tests, especially for testers with limited coding experience. Its integration with multiple frameworks and languages enhances its flexibility and compatibility.

Best for: Telerik Test Studio is an excellent choice for teams seeking a visual testing approach for API testing, complementing their existing testing workflows.

Pro tip: Combine Telerik Test Studio's visual testing with code-based tests to strike a balance between simplicity and flexibility, catering to testers with varying levels of technical expertise.

25. IBM Rational Integration Tester

What we like: IBM Rational Integration Tester provides advanced testing capabilities for APIs, services, and integrations. Its message flow simulation feature enables comprehensive testing.

Embracing the Future of API Testing with Cutting-Edge Tools

Choosing the right API testing tool is crucial for building functional and secure applications. The 25 tools mentioned in this article offer a range of features, support different programming languages, and provide essential security capabilities.

By considering your project's requirements and objectives, you can select the ideal API testing tool to streamline your testing process, ensure functional integrity, and enhance the security of your applications in 2023.