Top 15 API Testing Tools To Look For In 2023


December 20, 2022


December 21st, 2022

Do you know how popular apps like Pay with PayPal, Google Maps, Twitter Bots, etc. work? How do applications like eCommerce apps, and travel booking apps operate? It is the API that is working and bringing results.

An API is sort of a messenger that empowers two applications or two software units to share data and collaborate with each other. And to bring finesse to its execution, what is most significant is API testing tools. These tools for API testing are fundamental to ensuring a secure, reliable, efficient, performant, and robust API execution.

There are numerous competitive API testing tools that are known for their salient features. Before we go through them, let us understand the fundamental concepts of API testing and testing tools for API.

What is an API?

An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a set of tools, protocols, and routines to create software applications in which software components interact seamlessly with other software components. It is sort of a software bridge that helps secure communication between different elements of a software application.

Key Features of API
  • Faster insertion of content from other sites and applications
  • The expectation of future updates in components
  • Accelerates data exchange between software applications
  • Good developer support
  • Easily implementable, flexible, and simplistic

Interesting Read: A Comprehensive Guide To APIs – A Rage In Software Development

What is API Testing

API testing is an important aspect of software development that emphasizes thorough testing of APIs to ensure a seamless implementation. It can be manual or automated and integrates well with other forms of testing such as regression testing or functional testing. The prominence lies on the business logic layer of the entire architecture and not on the look and feel of an application.

This specified testing checks if the APIs are functioning as wanted or not and whether they can manage the load that is given to them when the software is implemented. It also finds out security hassles or bottlenecks in the APIs prior to execution. Here, the software is used to send calls to API, gather output and maintain a proper log.

The four main types of APIs are public, private, partner and composite. It tests if the API is returning the anticipated and satisfactory response and if it can manage security leaks with the time taken for providing a response.

API testing involves testing of:

  • SOAP web services – a firmer protocol for secure APIs
  • REST APIs – a set of regulations for scalable and lightweight web APIs
  • RPC – a practice for referring techniques with the assistance of JSON or XML message payloads

API testing includes a variety of testing types such as functional testing, validation testing, UI testing, security testing, load testing, error detection, penetration testing, and fuzz testing.

Key Benefits of Using API Testing Tools

API testing tools are indispensable when it comes to testing software applications with advanced technologies on a rise. With multiple APIs getting implemented in different components, there is increasing dependency, and failure of one of them could lead to a mismanagement of the entire application.

Here are some of the key advantages of the tools for API testing –

  • Quicker maintenance of tests and releases
  • Testing and feedback in advance for earlier output
  • Faster retrieval and solution of bugs and errors
  • Easy risk management
  • Better test coverage
  • Lower maintenance and testing costs
  • Support for languages like Java, PHP, Python, Ruby, JavaScript

How to Choose the Best API Testing Tools for your Project?

When there are so many tools for API testing, one often gets confused about which one to choose. Here are certain criteria that must be analyzed and pondered upon, while selecting the best API testing tools:

  • Available skill levels in the teams
  • Access to self-service reports and dashboards
  • Fundamental API needs based on application
  • Integration with CI/CD components
  • Capability to garner API documentation from the tool
  • Easy connection with other communication platforms
  • Option to execute asynchronous tests for better implementation
  • Faster sharing options


Top API Testing Tools for 2023

  • Katalon Studio
  • Postman
  • SoapUI
  • Karate DSL
  • Rest-assured
  • Testim
  • Assertible
  • vREST
  • Apigee
  • TestGrid
  • Tricentis
  • JMeter
  • API Fortress
  • Swagger
  • Speedscale

Let’s now have an overview of these API Testing Tools to know them better.

Katalon Studio:

Katalon Studio is a popular API testing tool, and test automation solution for web, mobile, and Windows applications. It is considered a strong yet simple tool that has been offering an easy-to-use user interface for the visualization of automation test situations and effective features for all types of applications. It supports REST, SOAP requests, and SSL client certificates. It is free to use with very active community support.

Key Features
  • Cross-platform with support for most OS and browsers
  • BDD customer support
  • Inbuilt keywords for lessening the work of building new tests
  • Effective focus on collaboration and testing
  • Native CI/CD integrations with Jenkins, DevOps, Docker, etc.


Postman is a known REST API testing tool that includes a set of tools to fasten the API lifecycle, starting from design, testing, documentation, and sharing of APIs. As a basic tool of Postman, the Postman API client helps you test APIs with the definition of complicated API requests for REST, SOAP, HTTP, etc. It has an easy-to-use REST client that offers an enriched experience.

Key Features
  • Executes well on Windows, Linux, Mac
  • Accessible for exploratory and automated testing
  • Transmission and receipt of REST information
  • Third-party support for Swagger, RAML formats, etc.
  • Powerful HTTP client for testing web services


SoapUI is one of the most popular API testing tools that test web services – REST and SOAP APIs and HTTP-based services. It is open-source and comes with a free package and a fixed package. Supported by SmartBear, creating, managing, and implementing comprehensive tests through SoapUI is easier and faster. It offers API functional testing, API performance testing, API security, data-driven testing, and test reporting.

Key Features
  • Supports REST, SOAP, GraphQL, and JMS protocols
  • Drag-and-drop functionality and point-and-click functionality
  • Support for asynchronous testing and data-driven testing
  • Quick and easy test creation
  • Third-party integration with other systems and tools

Karate DSL:

Karate DSL is a popular tool for API testing that is open source and combines API test automation, performance testing, UI automation and mocks into a distinct, integrated framework. It offers a readable, simple syntax that is designed for XML, HTTP, JSON, and GraphQL. There is a Java API for those who wish to integrate automation capabilities with data assertion competencies.

Key Features
  • Easy for non-programmers to write tests
  • Supports multi-threaded parallel execution
  • Reusing payload data and user-defined functions within tests
  • Designing scenarios for API-based BDD tests
  • Based on the popular Cucumber library


Rest-assured is a competent API testing tool that offers the effortlessness of using languages like Groovy, and Ruby in the Java domain. This open-source tool can be leveraged for validation and verification of the response of requests. It assists in testing REST APIs with the help of Java libraries and then integrates seamlessly with Maven. There are ways and means by which data can be fetched from the requests and responses, despite complicated JSON structures.

Key Features
  • Uses core Java fundamentals for simplistic implementation
  • Inhouse functionalities for codeless execution by users
  • Simple and effective automation testing of APIs
  • Extensive libraries and methods for automation
  • No need for extensive knowledge of HTTP


Testim is a popular UI and functional testing tool that is apt for API testing. It leverages the power of AI to assist in test implementation, maintenance, and design, a major part of which is API testing. It accelerates authoring, enhances quality, simplifies, and stabilizes testing through AI methods. It lessens maintenance, magnifies test analysis, and offers faster troubleshooting.

Key Features
  • Creation of API actions and validations for testing
  • Speedy and flexible authoring
  • Ideal for agile teams, customizing with code
  • Integration with CI tools and other development tools
  • Auto-improving functional testing platform


Assertible is considered an easy API testing tool for monitoring web services and there is support right from continuous integration to delivery pipeline. It is well-known, reliable and supports API test execution even after deployment. It offers automatic QA tools for testing and supervising web services around different deployments and environments. There is a trustworthy first line of defense opposed to a web service disaster.

Key Features
  • Automatically syncs API tests with the latest changes
  • Seamlessly integrates with tools of your choice
  • Automated QA pipeline for coding faster and noticing crashes
  • Ensuring your APIs are healthy and effectively operational
  • Good support for HTTP responses and validation with the assertion


vREST is a leading zero-code API test automation solution that offers an online solution for automated testing. It is a unified platform for functional, regression, and API testing for your project. It creates test suites with record/replay functionalities, test data, and specifications, making use of the least QA resources. There is a shorter learning curve with scriptless automation. It saves time, with help of efficient API automation techniques.

Key Features
  • Seamless data-driven testing
  • Integrates well with CI/CD tools
  • Test generation through Swagger, TestAPI, etc.
  • Fasters validation of REST APIs
  • Strong response authorization


Apigee is a cloud-based API testing tool, which is an integral part of Google Cloud. It empowers users in creating, managing, and securing APIs for any type of environment. It ensures a great deal of security, automation, and scalability. Powered by JavaScript, this tool manages performance hassles by proper tracking of API traffic, response time, and error rate.

Key Features
  • Easy creation of API proxies from Open API specifications
  • API-first integration with Apigee Integration
  • Deployment with reliable governance and control
  • Advanced security mechanisms for mitigating threats
  • Easy implementation of API architecture (REST, SOAP, GraphQL, etc.)


TestGrid is one of the best API testing tools that offers comprehensive, faster, and light weighted testing with minimal user interface design. It focuses on enhancing the security, quality, and functionality of APIs – be it commercial or open source. It is independent of programming languages and hence, easy for teams to create test cases without previous know-how of programming.

Key Features
  • Enhanced test coverage and lesser costs
  • Simple API automation for SOAP and REST calls
  • Plug n Play real-time user interface value declarations
  • Scriptless and API integration automation testing
  • Easy integration with chosen CI/CD tool for continuous testing


Tricentis is a leader in enterprise test automation and hence a known name when it comes to API testing tools. Tricentis Tosca goes by model-based test automation with script maintenance and quick regression testing. It is considered ideal for those who want Agile and DevOps integration. There is consistent support for diverse protocols like SOAP, HTTP, REST, MQ, etc. It supports comprehensive testing through cross-browser, packaged, and mobile applications.

Key Features
  • Codeless options for non-technical business users
  • AL & ML driven for quick and smart testing
  • Thorough testing for mission-critical applications
  • Reduced errors and increased visibility
  • Reusing API tests for service virtualization


Powered by Apache, JMeter is an open-source, Java application created to perform load test functional testing, and API testing. It is leveraged for static and dynamic resource performance testing. It works in an automatic manner with CSV files and offers an offline replay of test results. It is the best fit for web application performance and load testing. There is easy integration with Jenkins and hence it is easy to include API tests in the CI channel.

Key Features
  • Complete multi-threading framework
  • Full portability and 100% Java integrity
  • Fast test plan recording, debugging, and building
  • Access to complete and dynamic HTML report
  • Offline and caching analysis

API Fortress:

API Fortress offers a comprehensive testing platform with API mocking and different types of testing like integration testing, functional testing, etc. It is one of the most robust monitoring tools for REST and SOAP. Easy to use, it is ideal for continuous integration in API tests. It automatically generates code functions that turn out to be highly effective. There is standardized testing across teams.

Key Features
  • Removes redundancy and silos with greater transparency
  • Easy UI and ideal for those with the least technical knowledge
  • Compatibility with physical infrastructure and cloud-based
  • Integrated dashboards and reports
  • A platform for the complete API lifecycle, from design to launch


Swagger is a well-known API documentation and design tool for teams that are simplified for teams, enterprises, and users. There are separate tools for creating, updating, and sharing OpenAPI definitions, the industry standard for RESTful API design, with users. The Swagger tooling platform and ReadyAPI platform are key to simplifying the entire procedure of API test execution and API lifecycle.

Key Features
  • A collection of tools that use the Open API specification (OAS)
  • SwaggerHub for supporting OpenAPI workflows
  • Faster and enhanced delivery of products
  • Designing and documenting your APIs with scalability
  • Complicated load scenarios for analyzing API performance


Speedscale is a revolutionary, traffic replay framework for API testing in Kubernetes. It emphasizes stress testing APIs with real-world situations. It collects and replays traffic without the need for scripts. There can be load and chaos simulation and measurement of performance. There is continuous release velocity with testers increasing their release plans with real traffic conditions.

Key Features
  • Execution of traffic-based API tests for performance
  • Auto-generation of tests without scripting
  • Enhanced confidence in changes as part of continuous integration
  • Usage of mocks to reduce external dependencies
  • Automatic generation of assertions for comparing traffics
API Testing Tools: The Wrap-up

When it comes to software testing and especially API testing, different teams have different requirements. While choosing the apt API testing tool, it is significant to understand and analyze the details of what exactly is the need for the application.

Based on that and the parameters mentioned above, can a decision be taken as to which tool for API testing is best for the project. The list of API testing tools is going strong, and the future holds a bright side to it!


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