Firefox 41 for developers

To test the latest developer features of Firefox, install Firefox Developer Edition Firefox 41 was released on September 22, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Changes for Web developers

Developer Tools

Highlights:

All devtools bugs fixed between Firefox 40 and Firefox 41: note that many of these bugs, especially those relating to the performance tools, were uplifted to Firefox 40.

CSS

HTML

JavaScript

Interfaces/APIs/DOM

HTML Editing API

Events

Web Crypto

Canvas API

Service Workers

WebGL

  • The failIfMajorPerformanceCaveat WebGL context attribute has been added and can be set when creating a WebGL context with HTMLCanvasElement.getContext() to indicate if a context creation should fail if the system performance is low (Firefox bug 1164970).

WebRTC

  • Firefox no longer offers a default STUN server to be used if none are specified when constructing a new RTCPeerConnection. You'll need to provide one in order to successfully establish a WebRTC connection.

Miscellaneous

MathML

New default and fallback font handling

Mathematical formulas require special fonts. So far, these fonts were hard-coded in the mathml.css user agent stylesheet (which sets the font-family on <math> tag) and in the preference option font.mathfont-family (which sets the fallback fonts to use for stretchy and large operators). Firefox 41 introduces, an internal x-math language that is automatically set on the <math> tag as well as corresponding preference options (e.g. font.name.serif.x-math). The user agent stylesheet now sets font-family to serif on the <math> tag and the preference option font.mathfont-family is replaced with font.name.serif.x-math. All platforms now essentially use the same list of fallback fonts, with "Latin Modern Math" as first one. The default/fallback fonts can be configured from the standard per-language font preference menu. For more details, see Firefox bug 947654 and Firefox bug 1160456.

SVG

Audio/Video

Networking

Security

Changes for add-on and Mozilla developers

XUL

No change.

JavaScript code modules

No change.

XPCOM

Interfaces

No change.

Other

  • A new, internal, and chrome-context-only API to render the root widget of a window into a <canvas> has been added: CanvasRenderingContext2D.drawWidgetAsOnScreen(). This API uses the operating system to snapshot the widget on-screen. For more details see Firefox bug 1167477.

Older versions