Firefox 24 for developers

Firefox 24 was released on September 17, 2013. 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

CSS

  • The two values -moz-zoom-in and -moz-zoom-out of the cursor property have been unprefixed to zoom-in and zoom-out (Firefox bug 772153).
  • To match the specification, the keywords not, only, and, and or cannot be used as media types anymore (Firefox bug 757554).

HTML

  • The <track> element has been implemented behind the media.webvtt.enabled preference, and is disabled by default. (Firefox bug 833385).

JavaScript

DOM

Developer Tools

  • The Network inspector now lets you filter by content type (CSS/image/font etc.) and see the relevant size and load times.
  • The DevTools options panel to the left lets you disable/enable JavaScript temporarily.
  • Extension developers may use the new Browser Console for Chrome-level scripts (Replaces Error Console).
  • The source map syntax has been changed to use //# instead of //@ (Firefox bug 870361).

MathML

  • The dir attribute for controlling directionality of formulas on e.g., <math> or <mrow> elements is now equivalent to using the direction CSS property.
  • The equal sign ("=") is now stretchable.
  • The "updiagonalarrow" value for the notation attribute on <menclose> elements has been added.

Changes for add-on and Mozilla developers

  • Doc Shells have now the allowMedia attribute to disable media playing (Firefox bug 759964).
  • Sherlock search plugins in the application directory or profile won't be loaded anymore (Firefox bug 862143).

See also

Older versions