Design for developers
The only browser made just for developers, Firefox Developer Edition was created with your workflow in mind. Build, test, scale and more all from one place, for the first time ever.
Debug any browser
Inspect and debug your app across any browser or device with Valence — a powerful, pre-installed extension that you’ll only find in Firefox Developer Edition.
Pixel-perfect coding
Target screen sizes with the Responsive Design View and tweak your CSS on the fly with the built-in Style Editor for pixel-perfect coding.
All your favorite dev tools and more
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.
From: https://www.mozilla.org/