Design, debug, and test APIs locally or in the cloud

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.

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

Professional software tool for HTTP testing and debugging

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

Jest is a delightful JavaScript Testing Framework with a focus on simplicity.