Firefox 26 for developers

Firefox 26 was released on December 10, 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


  • The text-decoration-line property, still prefixed, now considers 'blink' as a valid value, though it doesn't blink the content at all (bug 812995).
  • The non-standard -moz-text-blink property has been removed (bug 812995).
  • Support for the image-orientation property, in its CSS Images & Values Level 4 version, that is with the from-image keyword and EXIF support, has been added (bug 825771).
  • Experimental support for position: sticky has been implemented and can be enabled by pref layout.css.sticky.enabled (bug 886646).
  • The text-align property now applies to the ::-moz-placeholder pseudo-element (bug 915551).


  • The HTMLSelectElement.selectedOptions property has been implemented (bug 596681).
  • In the <input> element of type email, values with domain labels longer than 63 chars are no more considered valid (bug 884332).
  • The HTMLInputElement.width and height properties now return 0 when the type is not image (bug 905240).
  • A <fieldset> element is now invalid, and can be styled using the :invalid pseudo-class, when one of the elements it contains is invalid (bug 717181).


ECMAScript 2015 implementation continues!




  • The inclusion of SVG glyphs inside OpenType, SVG-in-OpenType, has been updated to match the current version of the specification (bug 906521).
  • The SVGElement.ownerSVGElement() method doesn't throw anymore (bug 835048).

Development tools

Older versions