Firefox 26 was released on . While it has been developed to maintain compatibility as much as possible, the new version includes some changes affecting backward compatibility aimed at improving interoperability with the other browsers or following the latest Web standards. Here's the list of such changes — hope this helps whenever you test your sites or applications.
This article only explains the changes that may affect backward compatibility for websites. For the other new features and changes, please read the following documents:
Follow @MozWebCompat on Twitter for further updates.
-moz-text-blink has been removed in favor of
-moz-text-blink property has been removed. Instead, the standard, still prefixed
text-decoration-line property now takes
blink as a valid value. Actually it doesn't blink any content on Firefox though, from the perspective of accessibility. Note that the blink effect with
text-decoration:blink has been dropped with Firefox 23.
height now return
0 when the
type is not
height properties of an
<input> returned the dimension of the element. To comply with the spec, those properties now return
0 if the
type attribute is not
document.domain in a sandboxed
iframe is no longer allowed
Elements are no longer accessible with the old
id after being changed
id are accessible as
window.<id> DOM objects. Previously, such objects remained on
window even after the
id of the element was programmatically changed. This odd behavior has been fixed with Firefox 26. The
document.getElementById method, which is recommended to use in general, is not affected by this change.
MessageEvent has been updated
MessageEvent interface has been updated to comply with the latest spec. The
initMessageEvent method has been removed while the interface is now a constructor.
HTMLCanvasElement.mozGetAsFile has been deprecated
mozGetAsFile method on the
HTMLCanvasElement interface is now deprecated and will be removed soon. The standard
toBlob method can be used instead.
UserDataHandler has been removed
XBL-related methods have been removed
Various non-standard interfaces have been removed
- Bug 899388 – Remove XUL-related interfaces and ChromeWindow from content
- Bug 909340 – Hide XULElement from content
As part of the ongoing effort to standardize global objects, the following non-standard XUL-related interfaces have been removed:
The reserved words are no longer allowed as function names
All plug-ins except Flash now default to Click-to-Activate
Starting with Firefox 26, plug-ins require user interaction to be activated. With the exception of the popular Adobe Flash Player, all plug-in content embedded in a Web page is now disabled by default and enabled by a user's click. This change has been made in order to improve security and performance of the browser. See the Mozilla Security Blog and the Future Releases Blog for details. Web developers are encouraged to leverage modern Web technologies, including HTML5, to provide richer user experience. If that is not possible, see the site author guide for click-to-activate plugins.
A minimum width has been set for the browser window
To avoid a potential UI clipping issue with the upcoming Australis theme, a minimum width has been set for the Firefox desktop browser window. This size is
425px on OS X and
390px on other platforms. If you were resizing the window to test your mobile site, the convenient Responsive Design View can be used instead. The minimum width is not applied to popup windows, so this shouldn't affect content display.