Mozilla's new Firefox 4 browser has got off to a strong start, with 5 million copies of the new browser downloaded between its launch yesterday and 8am this morning.
Firefox 4 easily beat Microsoft's claim that users downloaded 2.4 million copies of its Internet Explorer 9 (IE9) in the first 24 hours of availability last week.
Mozilla has posted a real-time download calculator on its site.
When the new browser reached one million downloads, Mozilla developers and employees rang cowbells, cheered, and watched as someone dressed in a Firefox mascot costume danced around the room.
Tuesday's release marked the end of more than a year of development by Mozilla, which issued the first "alpha" edition of the browser in February 2010. Firefox 4 was originally scheduled to ship last November, but bugs and other delays forced it to announce in October that it would instead wrap up development early this year .
The code designated as final yesterday was identical to Firefox 4 Release Candidate 2 (RC2), a last-minute update that Mozilla issued last Friday.
Mozilla's Firefox 4 was the second major upgrade shipped by browser makers in just over a week. On March 14, Microsoft launched the final version of Internet Explorer 9 (IE9) .
Firefox 4 features a new tab manager, dubbed "Panorama", boasts an overhauled interface that resembles Chrome's minimalist design, and supports GPU acceleration to boost page composition speeds.
Hardware acceleration has become a point of contention between Mozilla and Microsoft. The latter has touted IE9 as the only browser to "fully hardware accelerate the entire Web platform," while Mozilla has criticized its rival for abandoning Windows XP users. IE9 runs only on Windows Vista and Windows 7.
Microsoft today again defended that decision.
"The developer community has been vocal that they want to push the Web forward," a Microsoft spokesman said in an e-mail. "The browser is only as good as the operating system it runs on and a browser running on a ten-year-old operating system tethers the Web to the past. The time has come to stop focusing on lowest common denominator, and to really push what's possible with innovations like full hardware acceleration."
Some Mozilla developers have used stronger words to describe Microsoft's argument that IE9 is the best browser on Windows.
"Microsoft's message that IE9 is the apex of what a browser can do with the GPU is nonsense," said Robert O'Callahan, a New Zealand employee of Novell who works full time on Mozilla's graphics infrastructure. In a post to his personal blog , O'Callahan said, "Microsoft's PR about 'full hardware acceleration' is a myth."
Mozilla technology evangelist Asa Dotzler was even more blunt . "Microsoft, stop making bull**** claims about hardware acceleration," Dotzler titled a post to his personal blog two weeks ago.
Users can download Firefox 4 for Windows, Mac OS X and Linux from Mozilla's site.