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.

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

Puppeteer is a Node.js library which provides a high-level API to control Chrome/Chromium over the DevTools Protocol.

Hoppscotch is an open-source API development ecosystem that helps you create and test your API requests saving precious time in development.

Monitor network requests and API failures with real-time insights

Voiden is a developer-first API client with local storage, Git-integrated, all based on markdown + offline support.