API Testing Add-on
Software Testing Tools & Resources
Largest collection of Resources and Tools for Software Testing Community

Advanced RestClient ExtensionFree version
Pa11yFree
Range of free and open source tools to help designers and developers make their web pages more accessible.
Contrast CheckerFree
Checks contrast for WCAG compliance

NVDAFree
Open source screen reader
WAVEFree
Web Accessibility evaluation tool

QAideFree
The Test Step Recorder