Firefox Browsers Products Who We Are Innovation Firefox Enterprise Nightly and Beta All Languages 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 Firefox Privacy Notice 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. Learn more 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 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 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 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. Start now Download the Firefox browser made for developers Firefox Developer Edition Firefox Privacy Notice Get the most out of Firefox Developer Edition Learn about Dev Edition and subscribe to the Mozilla Developer Newsletter. Your email address Sign Up Now Company Mozilla Manifesto Press Center Corporate Blog Careers Contact Donate Resources Privacy Hub Browser Comparison Brand Standards Support Product Help File a Bug Developers Developer Edition Beta Beta for Android Nightly Nightly for Android Enterprise Tools Follow @Mozilla Twitter Instagram Follow @Firefox Twitter Instagram YouTube Language Language aragonés عربي Asturianu Azərbaycanca Беларуская Български Bosanski Maya Kaqchikel Čeština Cymraeg Dansk Deutsch Dolnoserbšćina Ελληνικά English (Canadian) English (British) English Esperanto Español (de Argentina) Español (de Chile) Español (de España) Español (de México) فارسی Français Frysk Avañe'ẽ ગુજરાતી (ભારત) עברית हिन्दी (भारत) Hrvatski Hornjoserbsce magyar Հայերեն Interlingua Bahasa Indonesia Italiano 日本語 ქართული Taqbaylit 한국어 Lietuvių മലയാളം मराठी Melayu မြန်မာဘာသာ Norsk bokmål Nederlands Norsk nynorsk ਪੰਜਾਬੀ (ਭਾਰਤ) Polski Português (do Brasil) Português (Europeu) rumantsch Română Русский slovenčina Slovenščina Shqip Српски Svenska தமிழ் ไทย Türkçe Українська Tiếng Việt 中文 (简体) 正體中文 (繁體) Mozilla Website Privacy Notice Cookies Legal Community Participation Guidelines Visit Mozilla Corporation’s not-for-profit parent, the Mozilla Foundation. Portions of this content are ©1998–2021 by individual mozilla.org contributors. Content available under a Creative Commons license.