Firefox Developer Edition brings your core dev tools together with some powerful new ones that will extend your ability to work across multiple platforms from one place. It’s everything you’re used to, only better. And only from Firefox.
Following tools included
WebIDE, Responsive Design View , Valence, Web Audio Editor, Page Inspector, Web Console, JavaScript Debugger, Network Monitor, Style Editor.
https://www.mozilla.org/en-US/firefox/developer/
