What's New In Firefox 12

Martin Brinkmann
Feb 4, 2012

Mozilla is about to release Firefox 12 Aurora, after releasing Firefox 10 Stable and Firefox 11 Beta in the last two days. It is interesting to note that Firefox 12 is already offered on the Mozilla download website, but not through the browser's internal updater. Firefox Aurora users who do not want to wait can download the latest release from there to update the browser directly. It is not clear at this point in time why it is taken Mozilla that long to get Aurora installations to pick up the new version automatically.

The release notes, as usual, list only a handful of changes that have made it into the new version of the browser. At the top of the list is an improvement for Windows users who can now update Firefox easier thanks to one less User Account Control prompt during installation of the update.

The second new feature in this version of the browser is the new line numbering of the page source code. This is actually a pretty useful features for developers as it improves the source code's accessibility significantly.

Developers can now also use the column-fill and text-align-last CSS properties which the Mozilla developers have implemented in the browser. In addition, experimental support for ECMAScript 6 Map and Set objects have been implemented.

Firefox 12 comes with smooth scrolling enabled by default. The feature aims to improve the scrolling experience in the browser. Firefox users who experience issues with smooth scrolling or who prefer to work without the feature can disable it under Firefox > Options > Advanced > General > Use Smooth Scrolling.

smooth scrolling

Aurora users should pay attention to the known issues listing as well. Some Gmail users may for instance experience scrolling issues in the main Gmail window under this particular release.

Developers should take a look at the Mozilla Hacks article on the new release which highlights development related changes in Firefox 12.


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  1. Roman ShaRP said on February 6, 2012 at 10:35 pm

    So, as far as I understand this, there are no any significant features for non-developers end users in Firefox 12. :)

  2. Crodol said on February 5, 2012 at 1:03 pm

    When installing Aurora (firefox-12.0a2.en-US.win32.installer.exe) the installer is suggesting “C:\Program Files (x86)\Aurora\” as the target directory. Does it mean I “should” not overwrite the usual Firefox installation and run it separately? Or can I just install it over the official release (v10)?

    1. Martin Brinkmann said on February 5, 2012 at 1:06 pm

      I personally keep the directories separate. If you want to install it in the Firefox directory, I suggest you first uninstall Firefox (but keep the profile) and then install Aurora in the directory.

  3. B. Moore said on February 5, 2012 at 10:24 am

    How about the never ending famously known memory leak?

    still there I bet eh?

  4. XenoSilvano said on February 5, 2012 at 3:03 am

    Sometimes I use that up and down arrow keys to scroll through webpages and that feels pretty smooth.

  5. Midnight said on February 5, 2012 at 2:04 am

    As previously posted, not that anybody remembers, I’ve been using Firefox 12.0a1 (UX) Nightly since before Christmas, which just got updated today, to 13.0a1 and it’s runs as smooth as silk, without any hickups or flaws!

    Mozilla, in all it’s wisdom has applied all the tweaks needed in previous releases, which helped speed up the Browser, control the memory usage and a host of other small quirks! .

    I tried Aurora 12, but it just didn’t “feel” right and some features needed to be worked on, which is to be expected and should be peachy by the time the Final is released!

    All the Add ons, apart from the Kaspersky items are up to day and totally compatible.

    I’ll stick with UX until a better version is available!

  6. Threshold said on February 4, 2012 at 6:58 pm

    Martin, or anybody else, can you please explain what Auto-Scrolling and Smooth-Scrolling mean and the difference between the two?

    I have always had problems when scrolling pages in Fox especially when I use the sidebar.
    The browser hangs and sometimes the page gets detached in a new window (this especially annoys the hell out of me).


    1. Martin Brinkmann said on February 4, 2012 at 7:09 pm

      Auto-scrolling, when activated, lets you scroll by moving the mouse after you press down the middle mouse button. If you use the middle mouse button for other activities, you should turn it off. Smooth scrolling tries to make your scrolling experience more pleasant.

  7. Swapnil said on February 4, 2012 at 4:33 pm

    “Aurora users should pay attention to the known issues listing as well. Some Gmail users may for instance experience scrolling issues in the main Gmail window under this particular release.”

    NO!!! Mozilla has been mentioning “For some users, scrolling in the main GMail window will be slower than usual (see 579260)” for a long time now.
    Check known issues for Firefox 10-

    Check Known issues for Firefox 4!!!-

    The slow scrolling issue about Gmail exists in the ‘Known issues’ section of each new Firefox release.

    1. Midnight said on February 5, 2012 at 2:07 am

      No such problems with FF 13.0a1 (UX) Nightly!!

      GMail scrolls just fine! :)

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