Built for developers and testers alike, SoapUI is the only open source tool that covers the entire testing spectrum (functional, security, load, mocking).

RapidAPI for Mac is a full-featured HTTP client that lets you test and describe the APIs you build or consume. It has a beautiful native macOS interface to compose requests, inspect server responses, generate client code and export API definitions.

Playwright enables reliable end-to-end testing for modern web apps.

Mockoon is the easiest and quickest way to design and run mock REST APIs.

Cloud-scale performance testing. Effortless load testing and synthetic checks at scale. Cloud-native and open-source. The next evolution of performance testing.

Burp or Burp Suite is a set of tools used for penetration testing of web applications. It is developed by a company named Portswigger who make freely available a Web Security Academy which has a range of lessons on penetration testing.