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 HTMLSelectElement.selectedOptions property has been implemented (Firefox bug 596681).
  • In the <input> element of type email, values with domain labels longer than 63 chars are no more considered valid (Firefox bug 884332).
  • The HTMLInputElement.width and height properties now return 0 when the type is not image (Firefox 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 (Firefox 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 (Firefox bug 906521).
  • The SVGElement.ownerSVGElement() method doesn't throw anymore (Firefox bug 835048).

Development tools

Older versions