First introduced for Firefox 3.5, the revamped program has three main components: Activity Stream, Tab Center and Universal Search.
Activity Stream aims to make traversing your browsing history faster, which Mozilla believes will help you find important Websites and re-discover content quickly. When you open a new tab, Activity Stream surfaces your top sites along with highlights from your browsing history and bookmarks.
Tab Center is pretty straightforward: it displays open tabs vertically along the side of your screen rather than horizontally across the top of the window.
Mozilla says Universal Search “combines the Awesome Bar history with the Firefox Search drop down menu to give you the best recommendations so you can spend less time sifting through search results and more time enjoying the web.”
Search suggestions will also look a bit different; previously visited sites will be highlighted, while recommended sites will have a bit more info about the page, like top stories or featured content.
Currently available in English, Test Pilot can be downloaded via testpilot.firefox.com