Last Updated: April 22, 2024


Ifrah Khan


Modern software development relies heavily on APIs (Application Programming Interfaces). They act as the backbone, facilitating smooth communication and data exchange between various applications and services.

As the complexity of APIs grows, so does the need for rigorous testing to ensure their functionality, security, and performance. API testing is a crucial step in the software development lifecycle, guaranteeing that APIs meet the demands of modern applications and deliver a seamless user experience.

In this blog, we'll be exploring some of the best API testing tools. We'll delve into their features and use cases, empowering you to choose the ideal tool for your project's specific requirements. Whether you seek comprehensive test coverage or a solution that simplifies complex test scenarios, there exists a plethora of options to cater to diverse needs.


Before we check out the coolest tools for testing API, let's take a quick peek at the different types of API tests that help us build rock-solid software.

Types of API Testing

API testing encompasses a range of test types, each addressing specific aspects of API functionality as well as performance:

  • Functional Testing: Validates that API endpoints return the correct responses for various input parameters and scenarios.
  • Performance Testing: Assesses the API's ability to handle high volumes of requests and maintain responsiveness under load.
  • Security Testing: Evaluate the API's resilience against potential vulnerabilities and unauthorized access attempts.
  • Compatibility Testing: Ensures that the API functions seamlessly across different platforms, devices, and operating systems.
  • Documentation Testing: Verifies that the API documentation accurately reflects the actual behavior and usage of the API.

Now that you're familiar with the different types of API testing. Let's dive into the main part– the best API testing tools.


To complement your API testing efforts, don't forget to check out our insights on mobile app testing tools for a holistic approach to quality assurance.

Best API Testing Tools to Build Functional and Secure Applications 

After extensive research and evaluation, we've compiled a list of the best API testing tools that will empower you to develop exceptional apps.



Founded: Version 3.0 in 2019, version 1.0 was released in 2014

Developer: SmartBear

Supported Platform(s): Windows, macOS, Linux

ReadyAPI stands as a comprehensive API testing platform designed to streamline and automate testing workflows across multiple API types. Additionally, it caters to the needs of Agile and DevOps teams, enabling them to accelerate API quality and deliver exceptional software solutions.

Key Features of ReadyAPI:

  • No-code testing: ReadyAPI's intuitive interface empowers users to create, manage, and execute automated tests without requiring extensive coding expertise.
  • End-to-end testing: ReadyAPI facilitates comprehensive end-to-end testing, covering functional, security, and performance aspects of APIs.
  • Data-driven testing: ReadyAPI supports data-driven testing, enabling the utilization of external data sources to drive test cases and enhance test coverage.
  • Virtualization: Lastly, ReadyAPI's virtualization capabilities enable the creation of simulated API environments, facilitating testing without disrupting development workflows.

Uses Cases for  FReadyAPI Testing


PayPal, undoubtedly a global leader in online payments, utilizes ReadyAPI to ensure the security, scalability, and performance of its vast network of APIs. ReadyAPI's comprehensive testing capabilities allow PayPal to maintain the highest levels of reliability and trust for its millions of users.


Adobe, a renowned provider of creative software solutions, employs ReadyAPI to streamline its API testing processes and accelerate software delivery. ReadyAPI's integration with Adobe's continuous integration pipeline empowers the company to identify and resolve API issues. This is too early in the development cycle, ensuring seamless integration across Adobe's diverse product suite.


Toyota, a top automotive manufacturer, leverages ReadyAPI to enhance the quality as well as efficiency of its API development and testing processes. ReadyAPI's support for data-driven testing enables Toyota to utilize real-world data to drive test cases and ensure the robustness of its APIs in real-world scenarios.

Katalon Studio


Founded: 2016

Developer: Katalon Corporation

Supported Platform(s): Web, API, Mobile (Android and iOS), Desktop (Windows and macOS

Katalon Studio is a versatile and user-friendly test automation platform. It empowers teams to automate testing across a wide range of applications, including web, API, mobile, and desktop. Furthermore, its open-source nature makes it accessible to a broad audience. On the other hand, its comprehensive features and low-code approach enable teams to create and maintain test suites efficiently.

Uses Cases For Katalon Studio, a leading provider of travel booking services, utilizes Katalon Studio to automate testing across its diverse range of web, mobile, and API-based applications. Katalon Studio's cross-platform testing capabilities enable to maintain a consistent and reliable user experience across all platforms.


FPT Software, a global IT services company, employs Katalon Studio to streamline its software testing processes and accelerate delivery. Katalon Studio's low-code approach and integration with CI/CD tools enable FPT Software to automate testing early in the development cycle, reducing the time to market for new software solutions.


Siemens, a multinational conglomerate specializing in technology and engineering, utilizes Katalon Studio. It is to enhance the quality and efficiency of its software development and testing processes. Moreover, Katalon Studio's support for data-driven testing enables Siemens to utilize real-world data to drive test cases. This ensures the robustness of its software in real-world scenarios.



Founded: 2012

Developer: Abhinav Asthana

Supported Platform(s): Windows, macOS, Linux

Postman is a popular and versatile platform that empowers developers to streamline API development, testing, as well as documentation processes. It provides a user-friendly graphical interface, comprehensive testing capabilities, and a collaborative environment for API teams.

Key Features of Postman:

  • API development and design: Postman simplifies API creation and design, enabling developers to define API requests, responses, and data models.
  • API testing: Postman facilitates comprehensive API testing, covering functional, security, and performance aspects of APIs.
  • Mock API servers: Postman allows the creation of mock API servers, enabling testing and debugging without relying on actual production environments.
  • Documentation generation: Postman generates well-structured API documentation, ensuring easy access to API specifications and usage guidelines.
  • Collaboration platform: Lastly, Postman serves as a collaborative platform for API teams, enabling the sharing, commenting, and versioning of API definitions and test scripts.

Uses Cases For Postman


Netflix, a leading streaming entertainment provider, utilizes Postman to manage and test its vast network of APIs. Postman's collaborative features and comprehensive testing capabilities enable Netflix to maintain the high performance as well as reliability of its API-driven services.


GitHub, a popular code hosting platform, employs Postman to ensure the stability and security of its APIs. Hence, Postman's automated testing framework and integration with GitHub's continuous integration pipeline empower GitHub to detect and resolve API issues early in the development cycle.


Uber, a global transportation network company, leverages Postman to streamline its API development and testing processes. Postman's user-friendly interface and comprehensive testing capabilities enable Uber to accelerate the delivery of new features and maintain the high availability of its API-driven services.

Google Apigee


Founded: 2010

Developer: Acquired by Google in 2016

Supported Platform(s): Windows, macOS, Linux

Apigee is a cloud-native API management platform from Google Cloud. This platform enables businesses to build, manage, and secure APIs for any use case, environment, or scale. It provides a comprehensive set of tools and features for creating, deploying, and monitoring APIs, as well as for enforcing security policies and managing API traffic.

Key Features of Apigee:

  • API proxy layer: Apigee provides an API proxy layer that sits between backend services and clients. Allowing you to control, manage, and secure API traffic.
  • Traffic management: Apigee's traffic management features allow you to control the flow of traffic to your APIs, including throttling, routing, and load balancing.
  • Security: Apigee provides a variety of security features to protect your APIs, including authentication, authorization, and encryption.
  • Monitoring: Apigee's monitoring features allow you to track the performance and usage of your APIs, as well as identify and troubleshoot problems.
  • Developer portal: Apigee provides a developer portal that allows developers to discover, document, and consume your APIs.

Uses Cases For Apigee


Coca-Cola utilizes Apigee to expose its backend services to external developers. This allows them to build applications that integrate with its various brands and products.

The_Weather_Channel employs Apigee to manage its vast network of APIs, providing weather data and forecasts to a wide range of consumers and businesses.


eBay leverages Apigee to enhance the developer experience and ensure the security and reliability of its APIs, enabling seamless integration with its e-commerce platform.

Apache JMeter


Founded: 1998; latest version 5.4.1 on 22-01-2021

Developer: Apache Software Foundation

Supported Platform(s): Windows, Linux, Mac (any environment that supports JVM)

Last but not least on our list of best API testing tools is Apache.

Apache JMeter is a popular open-source load-testing tool. It is used by many organizations to test the performance and scalability of their applications. It is a powerful tool that can be used to simulate a wide range of user traffic, including both web and mobile traffic.

Use Cases for Apache JMeter


Google uses Apache JMeter to load test its vast network of applications, including Google Search, Gmail, and YouTube.


Amazon uses Apache JMeter to performance test its e-commerce platform,


Microsoft uses Apache JMeter to scalability test its cloud computing platform, Azure.


Founded: 2011

Developer: Swagger Software (previously SmartBear Software)

Supported Platform(s): Web-based with offline client options


Swagger is a comprehensive platform that empowers developers to design, document, and test APIs efficiently. Its core focus lies in the OpenAPI Specification, a common language for describing APIs, creating a standardized and collaborative workflow throughout the development cycle.

Use Cases for Swagger:

Foursquare: Utilizes Swagger to streamline API documentation and testing, ensuring consistent access and functionality for third-party developers.

Intuit: Leverages Swagger's collaborative features and automated testing to improve the efficiency and quality of their API development process.

Salesforce: Employs Swagger for API design, documentation, and testing, facilitating faster development and ensuring API stability for its extensive ecosystem of users.


Founded: 2013

Developer: Johan Haleby

Supported Platform(s): Java


REST Assured is a Java-based open-source library specifically designed for testing and validating RESTful web services. It seamlessly integrates with existing Java testing frameworks like JUnit and TestNG, providing a fluent and intuitive syntax for crafting comprehensive API tests.

Use Cases for REST Assured:

PayPal employs REST Assured for comprehensive testing of their payment APIs, ensuring reliability and security for financial transactions.

Netflix utilizes REST Assured to validate the performance and functionality of their streaming APIs, guaranteeing a seamless user experience.

Microsoft leverages REST Assured in testing their Azure cloud services, ensuring the robustness and scalability of their API-driven infrastructure.


Founded: 2016

Developer: Assertible, Inc.

Supported Platform(s): Cloud-based (web browser)


Assertible is a cloud-based platform specifically designed for API testing and monitoring. It offers a user-friendly interface, comprehensive testing capabilities, and built-in integrations for seamless integration into development and deployment workflows.

Use Cases for Assertible:

DigitalOcean relies on Assertible to monitor and test their API endpoints, ensuring high availability and performance for their cloud infrastructure services.

BetterCloud leverages Assertible for comprehensive API testing and monitoring, ensuring the reliability and security of their SaaS platform integrations.

LaunchDarkly employs Assertible for feature flag testing and validation, ensuring controlled rollouts and experimentation for their feature management platform.

Karate Labs

Founded: 2015

Developer: Peter Yu

Supported Platform(s): Java-based, but platform-agnostic through cross-platform runner


Karate Labs is not just another API testing tool; it's a revolutionary open-source framework that combines the simplicity of Gherkin syntax with the power of Java for comprehensive API automation. Imagine a world where tests read like plain English, code maintenance is minimal, and even non-programmers can contribute to API validation. That's the magic of Karate DSL.

Use Cases for Karate Labs:

Intuit embraces Karate for API automation due to its readability and ease of use, empowering testers across teams.

Expedia leverages Karate's versatility to handle complex API interactions and UI automation scenarios simultaneously.

eBay employs Karate for extensive API testing, ensuring the reliability and stability of their massive marketplace platform.

Also Read: Top API Integration Tools for Business Growth

Find the Best API Testing Tools With Us

Investing in a good API testing tool is an essential step for any business that wants to ensure the quality and reliability of its APIs. With the right tool in place, you can identify and fix bugs early on, prevent security vulnerabilities, and also ensure that your APIs are performing as expected. This will not only improve the user experience for your customers. It also helps you build a stronger reputation as a developer.

There are many great API testing tools available on the market, each with its strengths and weaknesses. The best tool for you will depend on your specific needs and budget. However, all of the tools I have discussed in this blog have a proven track record and can help you create high-quality APIs that will meet the needs of your users. Additionally, many professional API testing services can provide comprehensive testing and validation to ensure the reliability, performance, and security of your APIs.

Frequently Asked Questions (FAQ)

See the answers to some of our most commonly asked questions below.

There are many great tools for API testing; however, the best must support integration, reusability, scalability and running asynchronous tests to save time. A good API testing tool also comes with an easy user interface.

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