Welcome to your new favorite browser. Get the latest features, fast performance, and the development tools you need to build for the open web.
Firefox Developer Edition automatically sends feedback to Mozilla. Learn more
Firefox Browser Developer Edition
The browser made for developers
All the latest developer tools in beta, plus experimental features like the Multi-line Console Editor and WebSocket Inspector.
A separate profile and path so you can easily run it alongside Release or Beta Firefox.
Preferences tailored for web developers: Browser and remote debugging are enabled by default, as are the dark theme and developer toolbar button.
Firefox DevTools now grays out CSS declarations that don’t have an effect on the page. When you hover over the info icon, you’ll see a useful message about why the CSS is not being applied, including a hint about how to fix the problem.
Firefox is the only browser with tools built specifically for building and designing with CSS Grid. These tools allow you to visualize the grid, display associated area names, preview transformations on the grid and much more.
The new fonts panel in Firefox DevTools gives developers quick access to all of the information they need about the fonts being used in an element. It also includes valuable information such as the font source, weight, style and more.