The Apache JMeter™ application is open source software, a 100% pure Java application designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.

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

Free and open source. Solve accessibility issues before they reach your customers.

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.

Achieve effortless quality with zero coding, zero maintenance, and the autonomous power of the world's first open-source testing agent.