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

Streamline your API testing, integration testing and test data management.

Selenium automates browsers. That's it! What you do with that power is entirely up to you.

Simulate APIs, integrations, and environments at enterprise scale.

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

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.