Firefox 16 for developers

Firefox 16 shipped on October 9, 2012. This article lists key changes that are useful for not only Web developers to know about, but also Firefox and Gecko developers as well as add-on developers.

Changes for Web developers




  • Two new properties width and height have been added to the HTMLInputElement interface (bug 683855).
  • IndexedDB properties and methods have been unprefixed. (bug 726378)
  • The Battery API is now unprefixed.
  • The Vibration API has been unprefixed.
  • The non-standard Keyboard interface, prefixed as mozKeyboard, now has the Keyboard.setSelectedOption() and Keyboard.setValue() methods, as well as the Keyboard.onfocuschange. This interface, only available for Firefox OS, has been removed in Firefox 31.
  • The java and Packages global objects have been removed. See LiveConnect.
  • The CSSRule.type associated with CSSNamespaceRule has been updated from UNKNOWN_RULE (0) to NAMESPACE_RULE (10) (bug 765590).
  • WebSMS API: SmsRequest has been superseded by the more general DOMRequest.
  • The non-standard Element.scrollTopMax and Element.scrollLeftMax read-only properties have been added (Firefox bug 766937).
  • The second parameter of Blob(), when set to null or undefined, is now being handled as an empty dictionary (Firefox bug 7691119).



No change.


No change.


  • The lspace and rspace attributes of <mo> now correctly default to thickmathspace.


Developer tools

  • There's now a handy developer toolbar you can access by going to Tools > Web Developer > Developer Toolbar, or by pressing Ctrl-Shift-V (Cmd-Opt-V on Mac OS X). This toolbar offers a command line interface as well as buttons for quickly accessing useful tools. The graphical command line interface GCLI is easy to expand and additional commands are expected in the future. Type "help" to get a list of supported commands.
  • The Web Console now displays an error count so you can quickly see how much work you have ahead of you.
  • The Scratchpad now offers a list of recently opened files.

Changes for Open Web App developers

  • Initial Open Web App support has been implemented in the desktop versions of Firefox (that is, on Windows, Mac OS X, and Linux).

Changes for add-on and Mozilla developers

Interface changes

nsIPrivateDOMEvent has been merged into nsIDOMEvent. (Firefox bug 761613)

New interfaces

Removed interfaces

The following interfaces have been removed.