Hoppscotch : A free, online, open source API request builder
WebScarab : WebScarab is a framework for analysing applications that communicate using the HTTP and HTTPS protocols.
Browser Calories : The easiest way to measure your performance budget.
BackstopJS : BackstopJS automates visual regression testing of your responsive web UI by comparing DOM screenshots over time.
Seashells : Seashells lets you pipe output from command-line programs to the web in real-time, even without installing any new software on your machine. You can u...
The Web Developer extension adds various web developer tools to a browser. The extension is available for Chrome, Firefox and Opera, and will run on any platform that these browsers support including Windows, OS X and Linux.