Firefox 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.

Your system may not meet the requirements for Firefox, but you can try one of these versions:

Firefox Developer Edition is no longer supported on Windows 8.1 and below.

Please download Firefox ESR (Extended Support Release) to use Firefox.

Firefox Developer Edition is no longer supported on macOS 10.14 and below.

Please download Firefox ESR (Extended Support Release) to use Firefox.

Firefox Privacy Notice

Using Debian, Ubuntu or any Debian-based distribution?
You can set up our APT repository instead.

Firefox Developer Edition automatically sends feedback to Mozilla. Learn more

Firefox Developer Edition

The browser made for developers

All the latest developer tools in beta in addition to 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.

Inactive CSS
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.

Learn more

Firefox DevTools
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.

Learn more

Master CSS Grid
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.

Learn more

Fonts Panel
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.

Learn more

Design. Code. Test. Refine.

Build and Perfect your sites
with Firefox DevTools


Inspect and refine code to build pixel-perfect layouts.

Learn more about Page Inspector


Inspect and refine code to build pixel-perfect layouts.

Learn more about Web Console


Powerful JavaScript debugger with support for your framework.

Learn more about JavaScript Debugger


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


Unblock bottlenecks, streamline processes, optimize assets.

Learn more about Performance Tools


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.

Start now

Download the Firefox browser made for developers