Firefox 28 was released on March 18, 2014. 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
console.exceptionproperty has been added (bug 922214).
console.assertproperty has been added (bug 760193).
- App Manager: a new Manifest Editor was added.
- App Manager: the toolbox used for debugging apps is now embedded in the app manager UI.
- Web Console: added a "split console" mode - press Escape to quickly open the console in any other tool.
- Web Console: added a dark theme for the output.
- Debugger: simply hover over any variable or click on it to bring up a pop-up that displays the current value.
- Inspector: added a color picker in rules view and various tooltips.
- Browser Toolbox: allows add-on and platform developers to use almost all of the developer tools while targeting the browser itself.
More details in this post.
- Support for multi-line flexbox has been added (bug 939901).
- Longhand East Asian counter styles have been implemented (bug 934072).
- Experimental support for the
background-blend-modeproperty has been added, but is disabled by default (bug 841601).
nonevalue has been added to
- Support for the
:hoveruser action pseudo-class on pseudo-elements has been implemented (bug 922669).
<input type=number>have been implemented, disabled by default.
- ECMAScript 2015 implementation continues:
- A bug causing that
Object.getOwnPropertyNames()did not see unresolved properties of
Errorobjects has been fixed (bug 724768).
maybe. (bug 884275).
DocumentFragment.getElementById()method has been implemented. E.g.
KeyboardEvent.repeatattribute has been implemented (bug 600117).
new File(["foo"], "foo.txt")has been implemented. (bug 819900).
navigator.pluginsis no more enumerable, for privacy reasons (bug 757726).
- The two attributes
Window.screenYnow return CSS pixels (and no more device pixels) (bug 943668).
- The two methods
CanvasRenderingContext2D.drawCustomFocusRing()have been implemented. The preference
canvas.focusring.enabledmust be set to
trueto activate both (bug 540456).
willReadFrequentlycontext attribute for "
2d" canvas contexts has been implemented (see
HTMLCanvasElement.getContext()) (bug 884226).
- The following attributes and methods of
NavigatorIDhave been implemented on
WorkerNavigatorto allow their use in workers:
nextElementSiblingproperties has been removed from
DocumentType, because of compatibility problems (bug 932501).
- Support of the
mathvariantattribute has been added (bug 114365).
- Support of
SPDY/2has been removed.
Changes for addon and Mozilla developers
- The interface of DeferredTask.jsm has been changed, and the
cancel()methods have been removed (bug 940408).
- CSP was not enforced in sandboxed iframes. This has been fixed (bug 886164).
- The CSP 1.1 experimental
script-noncedirective has been implemented. The preference
security.csp.experimentalEnabledshould be set to
trueto enable this functionality (bug 855326).
- Firefox 27 for developers
- Firefox 26 for developers
- Firefox 25 for developers
- Firefox 24 for developers
- Firefox 23 for developers
- Firefox 22 for developers
- Firefox 21 for developers
- Firefox 20 for developers
- Firefox 19 for developers
- Firefox 18 for developers
- Firefox 17 for developers
- Firefox 16 for developers
- Firefox 15 for developers
- Firefox 14 for developers
- Firefox 13 for developers
- Firefox 12 for developers
- Firefox 11 for developers
- Firefox 10 for developers
- Firefox 9 for developers
- Firefox 8 for developers
- Firefox 7 for developers
- Firefox 6 for developers
- Firefox 5 for developers
- Firefox 4 for developers
- Firefox 3.6 for developers
- Firefox 3.5 for developers
- Firefox 3 for developers
- Firefox 2 for developers
- Firefox 1.5 for developers