Mozilla’s user experience (UX) team has unveiled a new and very different look for Firefox. For now we only have some very pretty mockups to feast our eyes upon, but in a couple of weeks Firefox 8 will migrate from the Nightly channel to Aurora — and after that, the new interface will begin to emerge in Firefox 9, 10, and 11. An exact time line isn’t yet known — Mozilla hasn’t actually started implementing the new interface yet — but we are told that the overhaul should be complete in the Nightly and Aurora channels before the end of they ear.

At first blush the UI mockups undoubtedly resemble Chrome, but if you take a moment and actually look at the new Firefox you will find a much richer, feature-rich interface than the spartan, one-button-fits-all Chrome — and in fact, it actually looks quite a lot like Internet Explorer 9. For a start, notice the Home icon that seems to have a permanent, very visible location on the left of the tab bar. This button will bring to the foreground Firefox Home, a new feature that will take a similar form to Chrome’s new tab page, but with more functionality. You’ll be able to open your favorite sites and launch web apps, but you’ll also be able to access other areas of the browser like the contact and account manager. The green Christmas tree to the right of the Home icon is what pinned tabs will look like.

Next, instead of a single star icon, the new Firefox interface has mashed together the “bookmark this page” button and the current bookmark drop-down list. It’s not obvious, but the Forward button has also disappeared (or it can be disabled), and the refresh button has joined the Awesome Bar — just like with IE9’s Omnibar.

The most significant change, however, is the new Settings (Action?) menu, which you can see in the screenshot below:

This will be an entirely new menu that provides easy access to add-ons, web apps, and primary surfing functions, and it completely replaces the Big Orange Firefox Button. This is a beautiful and graceful solution that removes the awful bottom-hugging add-on bar that plagues current incarnations of Firefox — but more importantly, it also provides a new home for every important feature that used to be found in the overloaded, dual-column, Firefox menu. As far as we know, the contents of this menu will change depending on the features that you most commonly use — and you’ll be able to add new buttons to it (if you want to access browser preferences, for example).

It isn’t shown in the UX mockups, but it looks like the space above the new menu, next to the unified Bookmarks button, will become the new add-on toolbar — very like Chrome, in fact. Unlike Chrome, however, this area will be able to house any Firefox button; not just add-ons. You will be able to drag the Print button into this add-ons area, for example, or Find, or Sync — or just populate it with icons for your favorite add-ons like Adblock Plus.

But why is Mozilla overhauling Firefox’s interface just a year after Firefox 4’s huge UI shake-up? To make Firefox more usable, basically. The vast majority of surfers only use a web browser’s primary interface: the address bar, tabs, refresh, the back button, and bookmarks. A smaller (but sizable) portion use features hidden behind menus, and a tiny fraction use add-ons or change off-by-default settings. The idea behind this new UI (which is called Australis, incidentally) is to make surfing very easy for the majority, but to also expose the features that surfers want to use but were previously buried behind the Orange Button of Doom. From another point of view, the new interface is very simple, but at the same time it retains Firefox’s legacy of complete customizability, with the new add-on bar allowing users to tailor the UI to their exact needs.

Finally it’s important to note that while the new UI looks very different, many of its fundamental features are in the same place: tabs, pinned tabs, the new tab button, the back button, and the bookmarks button are all similarly located. The only major change is the removal of the standalone search box — and yes, that might take a bit of getting used to.

View the entire set of Firefox 9 (or 10 or 11) UX mockups — and in other news, Firefox’s developer tools have also been overhauled by the Mozilla UX team — and boy do they look good. Presumably these too will start to appear in Nightly builds in the next few weeks.

Update: If you can’t wait to get your hands on the new UI, there’s a third-party Australis theme that you can install. Functionally it is nothing like the new mockups, but if you like the rounded tabs…