Built for those who build the Web
The only browser made for developers like you.
Firefox Developer Edition automatically sends feedback to Mozilla. Learn more
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Designed for developers
The only browser made just for developers, Firefox Developer Edition was created with your workflow in mind. Build, test, scale and more all from one place, for the first time ever.
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Debug any browser
Inspect and debug your app across any browser or device with Valence — a powerful, pre-installed extension that you’ll only find in Firefox Developer Edition.
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Pixel-perfect coding
Target screen sizes with the Responsive Design View and tweak your CSS on the fly with the built-in Style Editor for pixel-perfect coding.
All your favorite dev tools and more
Firefox Developer Edition brings your core dev tools together with some powerful new ones that will extend your ability to work across multiple platforms from one place. It’s everything you’re used to, only better. And only from Firefox.
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Visual Editing Tools
Visually edit CSS and HTML animations playing on the page from the Inspector panel. Verify alignment, dimensions and padding of any element using the Ruler and Measurement tools.
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DevTools Challenger
Use Developer Edition’s visual animation and CSS editing tools to explore the depths of the ocean and interact with the strangest of creatures.
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Performance Tools
Examine your web content’s frame rate, memory consumption and JS profile in a consolidated timeline view to help easily identify and troubleshoot performance bottlenecks.
Learn more about Performance Tools
Play the game on Codepen -
Page Inspector
Examine the HTML and CSS of any Web page and easily modify the structure and layout of a page.
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Web Audio Editor
Inspect and interact with Web Audio API in real time to ensure that all audio nodes are connected in the way you expect.
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Web Console
See logged information associated with a Web page and use Web Console to interact with Web pages using JavaScript.
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JavaScript Debugger
Step through JavaScript code and examine or modify its state to help track down bugs.
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Network Monitor
See all the network requests your browser makes, how long each request takes and details of each request.
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Style Editor
View and edit CSS styles associated with a Web page, create new ones and apply existing CSS stylesheets to any page.
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Responsive Design View
See how your Website or Web app will look on different screen sizes without changing the size of your browser window.
Learn more about Responsive Design View -
Valence
Develop and debug your apps across multiple browsers and devices with this powerful extension that comes pre-installed with Firefox Developer Edition.
Learn more about Valence