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12 Best API Testing Tools to Ensure Reliability But Not Issues in 2024

16 min read

January 8, 2024

12 Best API Testing Tools To Ensure Reliability But Not Issues In 2024

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Article Author

Alex Gurianov

CTO, System Architect

Long Story Short

Selecting the right API testing tool is A critical choice that directly affects the effectiveness and reliability of software development processes. There are many various types of API testing tools available. Each one has special advantages suited to a certain set of requirements.

The best API testing tool ultimately comes down to the unique requirements, tastes, and demands of a development team. Whether prioritizing simplicity, performance, or comprehensive API management, each tool in this diverse landscape has strengths. The optimal choice hinges on aligning these strengths with the unique demands of the development environment.

Do you need assistance choosing the right tool set? We are here to help you. Reach out to us, and we will choose the best API testing tools for your project.

This challenge is choosing the right automated API testing tools. The modern, ever-changing IT market offers a myriad of them. It helps companies streamline the testing lifecycle and enhance test coverage. However, this turns the choosing process into a real challenge.

Based on our experience, we gathered our TOP 12 API automation testing tools.

API Testing Challenge That Requires Special Attention


Postman simplifies API testing and quickly integrates it into the CI/CD pipeline, allowing for accelerated development, testing, and monitoring. The Postman API development environment includes collections, built-in tools, and workspaces. You can execute requests, debug, test, create, and document simulation scenarios, as well as monitor APIs.

Postman is useful for monitoring, debugging, testing, etc.


Postman's community offers extensive knowledge and documentation.

Community and documentation

Postman integrates well with other development tools and services. It makes it a valuable part of the development workflow.


Postman receives regular updates and improvements, ensuring relevance to evolving technologies.

Regular updates

The free basic pricing plan offers all the required capabilities.

Free basic plan


Postman can be resource-intensive. This affects performance on less powerful machines.

Resource intensive

Some developers prefer command-line tools. Postman's reliance on a graphical interface may not cater to everyone's preferences.

Dependency on a GUI

The quantity of requests, monitoring, and other sophisticated capabilities are restricted in the free edition.

Limited free tier



Swagger, now known as the OpenAPI Specification, is not an API testing tool per se; instead, it is a framework for describing RESTful APIs. It can also automatically generate client SDKs and documentation.

OpenAPI Specification is widely adopted and supported, promoting interoperability between tools and frameworks.

Open standard

Many enterprises use and support OpenAPI. It's like a collection of their knowledge from building many APIs over the years.

Huge user base

Generating client libraries in various languages reduces the effort developers need to use the API.

Client libraries


For beginners, understanding and using OpenAPI efficiently may be challenging.


Using OpenAPI may be seen as overkill for small, simple APIs, adding unnecessary complexity.




SoapUI is a cross-platform, open-source API testing tool. It allows testers to perform automated regression, functional, load, security, and compliance testing. It supports API testing because SoapUI is compatible with standard protocols such as SOAP/WSDL, JMS, REST, AMF, JDBC, etc.

SoapUI supports both SOAP and REST. It is suitable for testing a wide variety of web services.

Support for multiple protocols

Both beginners and experienced testers can create and execute tests efficiently.

Intuitive interface

SoapUI supports data-driven testing. This means testers can cover various scenarios using different input data.

Flexible data handling

You can extend SoapUI through plugins and custom scripts. It helps you tailor the tool to your specific needs.

Extensions and plugins


SoapUI is easy to start with. However, some of its features might have a steeper learning curve.

Complex features

Running extensive test suites or load tests can be resource-intensive.

Resource usage

The Pro version offers advanced capabilities but has an additional fee.

Pro version features



Insomnia is a simple tool for testing and debugging APIs. It enables you to send requests, view responses, and analyze errors. Insomnia supports a broad range of capabilities for interacting with various APIs: a set of HTTPs methods, calls to gRPC APIs, as well as custom methods with their parameters.

Insomnia is available on multiple platforms, including Windows, macOS, and Linux.

Multiple platforms

Insomnia includes a plugin system. It helps modify processes, add new features, or integrate additional tools.


Users can easily create HTTP requests using various methods (GET, POST, etc.). Additionally, they can customize headers, parameters, and body content.

Flexible request building

Insomnia allows users to generate code snippets in various programming languages based on the requests they create, facilitating integration with code projects.

Code generation


While Insomnia excels in testing RESTful APIs, it might not be the best choice for projects heavily reliant on other protocols like SOAP.

Focused on REST

Some functionalities required for extensive corporate API testing may not be available in Insomnia.

Enterprise-level features

Insomnia primarily focuses on creating and testing individual requests and responses. It may lack some of the advanced testing features found in more comprehensive testing tools.

Focused on request/response



Katalon Studio facilitates the automation of web, mobile, and desktop application testing as well as API testing. It is highly functional and operates on Windows, Linux, and macOS.

The user-friendly design of Katalon Studio is beneficial to testers of all experience levels.

Low learning curve

Katalon Studio includes a built-in object repository for managing test objects enhancing test maintenance and reusability.

Object repository

Katalon Studio supports BDD by integrating tools like Cucumber and Gherkin, enabling collaboration between developers, testers, and other stakeholders.

Behavior-driven development (BDD)

Katalon Studio offers features for organizing and managing test cases. It facilitates test suite scaling and maintenance for teams.

Test case management

Katalon Studio can integrate with popular version control systems like Git, facilitating collaboration and versioning of test scripts.

Version control

Katalon Studio provides built-in reporting features, offering insights into test execution results.

Test reporting


Katalon Studio supports scripting in Groovy. However, some users prefer more common programming languages.

Scripting language

Smaller teams or individual testers on a tight budget might find Katalon Studio's pricing plan unsuitable.

Pricing structure

Katalon Studio is suitable for many testing scenarios that are out of the box. More advanced customization options might be limited compared to tools with a more open architecture.

Advanced customization


Charles Proxy

Charles Proxy is a web debugging proxy application commonly used by developers, testers, and network administrators. It allows users to monitor, inspect, and manipulate network traffic between a computer or mobile device and the internet. Charles Proxy is widely used for various purposes, including monitoring and testing API requests and responses.

Charles Proxy offers a comprehensive view of HTTP and HTTPS traffic. This facilitates the understanding and debugging of client-server interactions.

Traffic monitoring and inspection

Developers can set breakpoints to intercept and inspect requests and responses. This simplifies debugging and analyzes how a server and an application communicate.


Charles Proxy supports SSL proxying, allowing users to inspect encrypted HTTPS traffic by acting as a man-in-the-middle. This is beneficial for debugging secure connections.

SSL proxying

It allows users to simulate different network conditions by throttling the bandwidth. This helps assess application performance on various network speeds.

Bandwidth throttling


Charles Proxy may be overwhelming for beginners, especially those new to network debugging.

Complexity for beginners

The full version of Charles Proxy is paid. Depending on the user's needs, the cost may be a consideration.




RestSharp is a popular open-source library. It simplifies making HTTP requests and handling responses and facilitates interaction with RESTful APIs in .NET projects.

RestSharp is designed with RESTful principles. It supports standard HTTP methods like GET, POST, PUT, DELETE, etc.

Support for RESTful principles

RestSharp supports various authentication mechanisms. This makes it versatile for interacting with APIs that require authentication.

Authentication support

Support for serializing and deserializing XML and JSON data is included in RestSharp. This simplifies interacting with RESTful APIs and processing complicated data structures.

Serialization and deserialization

RestSharp allows developers to make asynchronous HTTP requests, improving the performance of applications that handle multiple requests simultaneously.

Asynchronous support


RestSharp's documentation cannot be thorough enough. In specific use cases, users must rely on community resources.

Limited built-in documentation

RestSharp doesn't provide a standalone user interface or test runner. You need to integrate it into a .NET application.

Not a standalone tool

The open-source community works to create and maintain RestSharp. You have to consider that some security upgrades and new features won't be supported immediately.

Updates and maintenance


Apache JMeter

JMeter is a free, open-source tool for load, functional, unit testing, etc. It is primarily used for web applications, but it can also be used for basic performance monitoring.

Apache JMeter is used for performance testing and simulating multiple users. It is required to test the performance and scalability.

Performance testing

JMeter supports distributed testing, allowing users to scale their tests across multiple machines to simulate a larger number of virtual users and increase testing capacity.

Distributed testing

JMeter is compatible with many protocols and servers. These are LDAP, FTP, HTTP, HTTPS, SOAP, etc.

Rich set of protocols

JMeter allows users to create custom plugins and functions. It helps meet specific testing requirements.



JMeter's reporting capabilities may not be enough over some commercial performance testing tools.

Limited reporting

Individual testers often use JMeter. It’s because its collaboration features may not be enough as in some other testing tools for team environments.

Limited collaboration features



Paw is a powerful API testing and development tool designed for macOS. It provides a user-friendly interface for developing, testing, and debugging APIs. This tool allows businesses to check APIs, make requests, create client code, save API details, etc. Paw makes teamwork easier by letting users sync their tests.

Paw supports dynamic values and environments. Users can use it to design requests adaptable to various scenarios. This is useful for handling authentication tokens, variables, and dynamic data.

Dynamic values and environments

Drawing from predefined API requests, Paw can produce code snippets in multiple programming languages. This feature accelerates the development process.

Code generation

Paw supports environment variables and configurations. You can use different parameters for testing in various environments.

Environment variables and configurations

Paw supports importing and exporting API requests and configurations. It facilitates collaboration and sharing of test cases among team members.

Import and export


Paw is available only for macOS, which limits its usability for users on other operating systems.

macOS exclusive

Paw offers a free trial. But you must purchase a license to use all of its features.

Paid software



Karate combines API testing, test automation, and performance testing. It streamlines API testing by employing a straightforward syntax based on the Gherkin language.

Karate uses a BDD syntax. This makes it accessible to technical and non-technical team members.

BDD syntax

Karate supports data-driven testing. It simplifies changing and parameterizing test scenarios depending on various data types.

Data-driven testing

While Karate itself is primarily based on the Java Virtual Machine (JVM), it allows the inclusion of JavaScript for scripting purposes, providing flexibility for users with JavaScript expertise.

JavaScript integration

Karate minimizes the amount of boilerplate code needed for API testing. It simplifies testing for non-programmers.

No coding required

Karate can handle API and performance testing within the same framework. It reduces the need for separate tools for different testing phases.


Karate generates detailed HTML reports that include information on test results, scenarios, and timelines, aiding in the analysis of test execution results.

Detailed test reports


Karate is pretty popular but still doesn’t have an extensive community or ecosystem. It could result in fewer resources and third-party integrations.

Limited ecosystem and community support

Compared to general-purpose programming languages, Karate might be less extensible for implementing custom functionality or integrations beyond its built-in capabilities.

Less extensible

Karate is built on the JVM. Utilizing many platforms or programming languages could be a limitation.

Java dependency