Firefox Developer Edition 64.0

Firefox Developer Edition is a version of Mozilla product created specifically for software developers. It has several new features and unique functionality. This version of the browser can actually operate independently of standard Firefox and family browsers like Safari. It borrows the default colors and interface elements from the developer tool set which makes the interface itself easy to use and navigate if you have any experience in development of products in this line.

Some of the new tools, like the Valence add-on, give you access to Firefox developer tools for other browsers. Other notable features include things like Responsive Design View, which lets users change screen sizes in real-time without adjusting size of their browser window. Then, there's the style editor, a tool that lets you edit CSS page styles, to create your own variations and apply existing CSS style sheets to other pages.

Firefox Developer Edition is an all-in-one toolbox for people into browser development. It has all the basic tools and some of the more advanced features one would expect from a software bundle like this.

v64.0 [Oct 17, 2018]
Developer tools
- The Accessibility info-bar has been enhanced to include information about the color contrast ratio of text or images on the web page. (bug 1473037).
- Responsive Design Mode device selection is now saved between sessions (bug 1248619).
- The Developer Tools GCLI has been removed (bug 1429421).
HTML
- No changes.
CSS
- CSS Scrollbars has been enabled by default (bug 1492012).
- Implemented Interaction Media Features including pointer:coarse (bug 1035774).
- The non-standard -moz-box and -moz-inline-box display values have been hidden from web content (bug 1496961).
- The non-standard ::-moz-tree pseudo-elements have been hidden from web content (bug 1496961).
- The layout.css.filters.enabled preference has been removed; CSS filters can no longer be disabled (bug 1408841).
SVG
No changes.
- In the WebAssembly.Global constructor, if no value is specified, a typed 0 value is used, as specified by the DefaultValue algorithm (bug 1490286).
DOM
- A number of changes related to the Fullscreen API have been implemented:
The API has been unprefixed (bug 1269276).
The Element.requestFullscreen() and Document.exitFullscreen() methods both now return a Promise which is resolved when the mode change is complete (bug 1188256 and bug 1491212).
Previously, fullscreenchange and fullscreenerror events were went to the Document first, then the Element. This has been reversed, so that the element gets the event first. This matches the latest specification as well as the behavior of Google Chrome (bug 1375319).
DOM events
- Media, Web Audio, and WebRTC: The PannerNode.refDistance, PannerNode.maxDistance, PannerNode.rolloffFactor, and PannerNode.coneOuterGain properties now correctly throw exceptions when set to values outside their accepted ranges (bug 1487963).