Firefox Quantum: 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 — English (US)

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Firefox Developer Edition — English (US)

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Firefox Privacy Notice

Firefox Developer Edition automatically sends feedback to Mozilla. Learn more

Faster Performance

A Next-Generation CSS Engine

Firefox has been rebuilt from the ground up to be faster and more powerful than ever. This includes a new CSS engine that has state-of-the-art innovations and is blazingly fast.

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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

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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Convenient Features

Shapes Editor

Firefox DevTools has a brand new shape path editor that takes the guesswork out of fine-tuning your shape-outside and clip-path shapes by allowing you to very easily fine-tune your adjustments with a visual editor.

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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
Web Audio

The only developer tool for inspecting the Web Audio API. Learn more about Web Audio Editor
Scratchpad

Edit, write, run and execute JavaScript in real time. Learn more about Scratchpad
Style Editor

Edit and manage all your CSS stylesheets in your browser. Learn more about Style Editor