Implementing Australis, the new theme for Firefox, is one of the top goals for the desktop team this quarter. As a result, I've recently taken over work on the tab strip visual redesign portion of the project. At this point the tab shape and styling has been implemented on Windows and is undergoing review so it's a good time for testing from a wider audience so the feature can get some polish before development starts on OS X and Linux in the upcoming weeks. The following is a screenshot of a build with the the latest patch.

To test the new design, install the Firefox UX Nightly on Windows (exe, zip). The changes are in code review and there is still some work to be done in follow-ups but at this point there aren't any known bugs which will hinder browser usage so go ahead and give it a try. Polish for background themes and Windows 8 will be added in follow-up bugs.

Some of you have been waiting for Australis since the designs were created over a year ago and you may be wondering why it takes so long to be implemented. The answer is that Firefox UI is very flexible and tries to adapt to various configurations and getting this right with a new theme can be a complex process. Here are just some of the variables that are taken into account while balancing the aesthetics, complexity, and performance of the implementation:

Operating system version/theme

Classic, XP, Aero Basic, Aero Glass, Windows 8, High Contrast

Background themes for Firefox

Window state - maximized/restored/fullscreen

Tabs in the titlebar

Tabs on top/bottom

Integration with system color, font and DPI settings

Tab overflow

Pinned/app tabs

Customization mode

Text direction – Left-to-right vs. right-to-left

Customized toolbar buttons

Tab drag-and-drop

Menu bar visibility

You can follow the remaining Australis tab work from the meta bug. Report issues with the current implementation in the comments on this post or in the bug (if they haven't already been covered there or in the etherpad).