Welcome to Firefox Developer Edition

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

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.

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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.

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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.

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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.

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Speak up

Feedback makes us better. Tell us how we can improve the browser and Developer tools.

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Get involved

Help build the last independent browser. Write code, fix bugs, make add-ons, and more.

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