Firefox Browser Developer Edition
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.
New Tools
Inactive CSS
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.
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New Tools
Firefox DevTools
The new Firefox DevTools are powerful, flexible, and best of all, hackable. This includes a best-in-class JavaScript debugger, which can target multiple browsers and is built in React and Redux.
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Innovative Features
Master CSS Grid
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.
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Faster Information
Fonts Panel
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.
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Design. Code. Test. Refine.
Build and Perfect your sites with Firefox DevTools

Inspector
Inspect and refine code to build pixel-perfect layouts.
Learn more about Page Inspector

Console
Track CSS, JavaScript, security and network issues.
Learn more about Web Console

Debugger
Powerful JavaScript debugger with support for your framework.
Learn more about JavaScript Debugger

Network
Monitor network requests that can slow or block your site.
Learn more about Network Monitor

Storage panel
Add, modify and remove cache, cookies, databases and session data.
Learn more about Storage Panel

Responsive Design Mode
Test sites on emulated devices in your browser.
Learn more about Responsive Design View

Visual Editing
Fine-tune animations, alignment and padding.
Learn more about Visual Editing

Performance
Unblock bottlenecks, streamline processes, optimize assets.
Learn more about Performance Tools

Memory
Find memory leaks and make your application zippy.
Learn more about Memory Tools

Style Editor
Edit and manage all your CSS stylesheets in your browser.
Learn more about Style Editor
Speak up
Feedback makes us better. Tell us how we can improve the browser and Developer tools.
Join the conversation
Get involved
Help build the last independent browser. Write code, fix bugs, make add-ons, and more.
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