Right on schedule, Mozilla Corp. shipped Firefox 3.5 about a minute ago, at about 11:20 am Eastern time. The new version adds performance improvements, privacy features, support for embedded video, and more. It comes into the world facing a more crowded and competitive market than before, as alternatives such as Google Chrome and Safari have emerged as viable alternatives to both Firefox and Microsoft Internet Explorer.The chief new feature of Firefox 3.5 is the TraceMonkey JavaScript engine. JavaScript is becoming increasingly important as the engine driving advanced Web applications like Gmail and Google Maps; TraceMonkey is designed to make those kinds of applications run faster.

Switch on private browsing, nicknamed "porn mode," and you won't leave a trace in your browser of sites that you visit while private browsing is active - no history, and no saved passwords. Note that you will leave a trail on the server logs of the sites you visit, as well as any snoopy software your network administer or Internet service provider may have installed.

Firefox 3.5 includes support for more than 70 languages, embedded HTML 5 video and audio, including native support for Ogg Theora video and Vorbis audio.

Another intriguing new feature: Location-aware browsing. The tool uses your system's built-in geolocation hardware - that's assuming your system has that of course - to allow you to share your location with other people. You can set it to share your pinpoint location, or just your general. Geolocation support will open the door to location-aware Web applications.

Firefox 3.5 faces new browser challengers. While Internet Explorer's market share has slipped fast, by 8% percentage points to 65.5% in the past year, Google Chrome, Apple Safari, and the venerable Opera browser are all emerging as contenders to Firefox - alternatives to the alternative, so to speak.

Firefox has gained about 3 percentage points to 22.5 percent in market share, according to Net Applications' statistics since July 2008, and Firefox backer Mozilla doubtless hopes for more gains with the release of Firefox 3.5 planned for Tuesday. But Apple's Safari and Google's Chrome each gained 2 percentage points, to 8.4 percent and 1.8 percent, respectively, indicating a growing appetite for alternatives to Internet Explorer that's not completely met by Firefox. Opera stayed flat at about 0.7 percent.

In short, Firefox isn't the only scrappy underdog in town, and Firefox fans' easy us-versus-them polarization is transforming into a more complicated multilateral equation.

Now if you'll excuse me, I think I'll go upgrade.

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