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.

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

Automate API workflows. Chain HTTP requests. Validate. Zero code.

Swagger UI allows anyone — be it your development team or your end consumers — to visualize and interact with the API’s resources without having any of the implementation logic in place

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.