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Firefox 28 Beta 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:
This list may be updated until the release of the final version on , so please check back later. Follow @MozWebCompat on Twitter for further updates.
showModalDialog has been deprecated
Make sure the
deep argument is specified for
- Bug 937465 – Add a warning when cloneNode/importNode is used without a boolean argument on a node with children
document.importNode methods take the boolean
deep argument. It's optional in the DOM4 specification, and if omitted, these methods acted as if the value of
true. But this behavior has been changed in the latest spec, and if omitted, the methods will act as if the value was
false. Though It's still optional, Firefox now warns developers in console not to omit the argument for the forward compatibility.
History objects now throw if the
document is inactive
The spec of the
History interface has been updated, and the properties and methods now throw a
SecurityError exception when those are called on an inactive
document. It would be a problem if you are manipulating
window.history in an
Global variables with the same name as
window properties are no longer accessible
A typical impact of this change has been reported as Bug 943958. A code like
var name = 1 no longer works as expected, instead
name will return a string
'1' because of the
window.name property. Web developers should avoid using global variables with the same name as
Update: This change has been backed out because the spec is in flux at this time.
SPDY/2 support has been dropped
The support of SPDY Protocol Draft 2 has been removed. Web sites should upgrade to SPDY/3 or 3.1.
canPlayType('video/webm') now returns
canPlayType method of the
HTMLMediaElement interface has been updated to comply with the spec.
canPlayType('audio/webm') now return
'maybe' instead of
'probably', because media can be encoded with a codec that Firefox doesn't support. If a codec is specified in the
type argument, the method returns
'' (empty string) depending on the codec. For example,
canPlayType('video/webm; codecs=vp8') returns