A very exciting set of changes is landing in Firefox Nightly. We’ve been calling the project Australis, but, simply, it’s the next iteration of the Firefox user interface. It’s not quite finished, and it needs more polish, which is exactly why we’re so eager to get it out to a wider set of the community.

So, what is Australis?

1. It’s the most beautiful and detail-obsessed iteration of Firefox’s visual design yet: modern, clean, and comfortable.

2. More fundamentally, it’s a streamlining and simplification of the default interface, to declutter and better focus on how people use a browser today.

3. Finally, it includes a new simple way to customize the browser and make it your own.

There are also many side-benefits: a better more extensible interface model that will accommodate future features and additions; a simpler presentation of add-ons as equals to built-in browser features; and a familiar look and feel across all our platforms so that Firefox feels like Firefox everywhere. We’ll be writing more about all of these in future posts.

Need a quick concrete demonstration of what we mean? Here’s a two minute overview and walkthrough:

Let’s take the main three points one at a time and explain what we mean.

1. Detail and beauty

Australis is largest refinement of the Firefox interface in a long time, and it touches almost everything, from the big picture of overall layout to the tiny corners of icon design.

One of the most noticeable changes is our tab shape. Ours is Firefoxy — organic, friendly, and fluid — and a good fit for the general feel of Firefox.

As important, though, is the distinction between foreground and background tabs. Background tabs are visually de-emphasized, leaving a space that’s uncluttered and calm, where it’s quick and easy to see which tab is currently selected. Tabs also slide forward into focus as you mouse over them, so you can better see where you’re heading.

Incidentally, the less cluttered tab bar means that lightweight browser themes look the best they ever have.

2. Streamlining and simplification

Firefox has grown with the web, bringing new tools and capabilities — tabbed browsing, one click bookmarking, download management — to the forefront the whole time. But you can’t just keep adding without pausing, taking stock of what’s broadly used and what’s not, and cleaning up. Firefox, like all software, has accumulated baggage over time, but our users have become seasoned light travelers.

Where does this simplification show up? You’ll see it in the streamlined way that Firefox’s tabs sit higher in the titlebar, getting out of the way and leaving more screen space for web pages.

You’ll also see it in how carefully and sparingly the default toolbar is filled. Some examples have already landed in earlier releases, like the forward button that only appears when there’s somewhere to go forward to, and the download button that shows progress when that’s relevant and hides it otherwise. New, landing in Nightly now, you’ll see this in a more prominent one-click bookmarking button paired with a button to get at those bookmarks.

These always-used-by-everybody controls are front and center. Widely- but less frequently-used controls are quickly close at hand in the new (and touch friendly!) menu at far right. For the rest, the 2% use-cases, new simpler customization is easier than ever to find and use.

3. Easy Customization

Firefox can’t simplify by just removing things and still be Firefox — the same less isn’t more for everybody, and Firefox has been successful by being the browser that does things that people, including power-users, want. It’s even in our Firefox Design Values (PDF) (see You Help Make It).

We realized that Australis was the perfect time to make browser customization easier and more discoverable. This provides power and control to people who have specific feature needs and allows them to create their own perfect setup while giving new users an understandable starting point.

To this end, a new, easy and fun-to-use customization mode is very prominent in the interface. We’re hoping that it will serve as an on-ramp for more users than ever to make Firefox into exactly what they need. It works with features we ship by default as well as with features that people add through add-ons. We’ll dive deeper into the customization mode in a future Firefox UX blog post.

That’s the new Firefox – beautiful, streamlined, and customizable.

What’s landed in Nightly is enough for intrepid users to have a solid day-to-day experience and help us finish Australis off — there’s more to come (interactive mockup!), so please keep trying it out!

— Madhava Enros and Stephen Horlander, for the Firefox User Experience team