Testsigma is one of the best tools for API testing in the market today. It provides a user-friendly interface, requires no coding skills, and supports the testing of RESTful and SOAP APIs. Testsigma also allows for cross-browser testing, mobile testing, and end-to-end testing, making it a comprehensive solution for testing applications. Other popular API testing tools include Postman, SoapUI, REST-assured, and Assertible.