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.

Checks web UI for browser compatibility (Compliance with Can I Use?)

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

WebLOAD – Performance and Load Testing for the Most Challenging Web Applications

Anyone on your team can load test with instant playback, an easy-to-use interface, and real browsers for reliable data.

Gatling is a powerful open-source load testing solution that integrates with your development pipeline. It includes a web recorder and colorful reports.