Application programming interface (API) testing is similar to software testing that checks the functionality, reliability, performance, and security of the APIs. Focus of API testing is to check if the developed API meets the expectation or not. Nowadays, APIs play a very important role in successful digital transformation, this increases the demand for API testing at a bigger level. According to Google trends, API testing has been growing continuously over the last couple of years. It is not easy to test APIs manually. Therefore, you need to use an intelligent and easy-to-use automation tool to test the APIs. Testing tools help us to reduce time to market the application and improve effectiveness and productivity. In this article, I have covered a list of The Best API Testing Tools in 2020.

Soap UI

According to Piyush Jain, founder of Simpalm a mobile app development company, Soap UI is one of the oldest and matured API testing tools available in the market. It is a headless functional testing tool dedicated to API testing, allowing users to test REST and SOAP APIs and web services easily. SoapUI is offered as a free and paid package. Using the free package, users can get full source code and build their preferred features. On the other hand, the Pro package supports native CI/CD integration and powerful data-driven testing.


  1. Drag and drop, point and click option reduce testing time.
  2. Reusability of the script.
  3. Easily create custom code.
  4. Powerful data-driven testing.

For advanced features, you need to switch the SoapUI pro version($695 per year).


Postman is one of the best tools for API testing. It provides more and better features than others and has very good reviews from its users. It offers three plans. Free plan for individuals, postman pro plan for a team of 50 members that will cost $8 per user per month, and last is postman enterprise, it can be used by a team of unlimited members that will cost $18 per user per month.


  1. It is easy to use because of its user-friendly interface.
  2. It helps in both automated and exploratory testing.
  3. Easy to use REST clients.
  4. It supports Swagger and RAML formats.
  5. It does not require learning a new language.


Swagger has been launched recently and is growing in popularity. It will guide you through the entire life cycle of an API. This tool allows users to make functional, performance, and security testing of an API. Swagger inspector makes it easy for developers and QA to manually validate and explore APIs in the cloud. LoadUI pro helps to perform load and performance testing.


  1. Swagger Inspector allows you to inspect API request-responses and make sure they performed well.
  2. Complex load scenario helps to check the scale and performance of APIs.
  3. Supports services from REST, SOPA or Graph QL.

REST Assured

REST Assured is an open-source tool. It makes testing of REST services in java domain easy. It has a bunch of bake-in functionalities, which means users don’t have to code things from scratch. For REST Assured users not necessarily need to be an HTTP expert.


  1. It supports the syntax of BDD Given, When, Then.
  2. Seamless integration with serenity automation framework.
  3. It provides some baked-in functionality.
  4. Users don’t need to be an HTTP expert.

Katalon Studio

Katalon Studio is one of the best automation testing tools for API, web, and mobile applications. The main advantage of Katalon studio over others is the capability of combining UI and API web services for multiple platforms like Microsoft, Mac OS, and Linux. It is a free and robust automation tool. It also offers paid services for businesses and enterprises. It supports both SOAP and REST requests with various types of commands and parameterization functions.


  1. It supports both SOAP and REST requests.
  2. It supports the data-driven approach.
  3. It supports CI/CD integration.
  4. It can be used for both automated and exploratory testing.
  5. Have hundreds of built-in keywords for creating test cases.

Suitable for both beginners and experts.

Karate DSL

Karate DSL is an open-source platform for API testing. It is based on the cucumber library. With the help of Karate DSL, you can test the web services by writing tests in domain-specific languages. It is a new API testing tool design for automated API testing. To run this tool you don’t need to be an expert in the programming language, basic knowledge of HTTP, XML, X path, JSON will work.


  1. It can run a test and generate reports like any standard java project.
  2. Tests are easy even for the User with a non programming background.
  3. It supports configuration switching and multithreaded parallel execution.
  4. It reuse payload-data for API testing.
  5. It is built on top of Cucumber- JVM.


API testing tools are now trending in automation testing and more tools will be developed to fulfill the demands. Choosing the best tool is a very tough task, but the good thing is that we have many more choices than before. With the help of the above lists, You can easily choose the best API testing tool according to your requirements as well as considering the pros and cons of each tool.

Larry has been writing Android and iOS app reviews for about 4+ years. In addition to app reviews, he conducts developer interviews, reports on new apps, and general mobile news. In addition to his own blog, App Review Central, Larry is a contributor to numerous other Android and iOS app review sites.

Larry Sullivan