"With IE9, Firefox 4, and Chrome 10 all hitting their final releases recently, drawing instant comparisons around downloads or initial usage is a natural temptation, but unfortunately you can't do it quite yet," said Ryan Gavin, senior director of IE marketing.
A day after IE9's 14 March launch, Microsoft touted the 2.3 million copies that had been downloaded in the first 24 hours. A week later, Mozilla shipped Firefox 4, logging 7.1 million downloads the first day, another 8.75 million the next. The latter exceeded the 2008 record of eight million that Mozilla set with Firefox 3 in 2008 for the most software downloads in a 24-hour period.
But in a Tuesday blog post, Gavin contended that differences in how the browser makers offer upgrades makes early comparisons meaningless, and that IE9 will only get rolling next month when Microsoft enables Automatic Updates on its Windows Update service.
Thus far, Microsoft has pushed IE9 via Windows Update only to users already running the beta or release candidate builds of the browser.
"In the case of Firefox 4 and Chrome 10 their update mechanisms are turned on as part of their initial release to web (RTW)," claimed Gavin.
That's not entirely true.
Although Google updates the "stable" build of its Chrome silently in the background - including Chrome 10, which launched three weeks ago - Mozilla has not yet switched on an upgrade offer for users running the older Firefox 3.6 browser.
Instead, Firefox 3.6 users must first update to the newest version of that edition, then manually check for an update to see the Firefox 4 offer.
Traditionally, Mozilla kicks in the offer - which it calls a "major upgrade" - 60 to 90 days after the launch of a new browser. But a major upgrade offer for Firefox 4 may appear "soon," a Mozilla spokeswoman said Wednesday.
Because IE9 won't reach all users until June when the Windows Update offer wraps up, usage share comparisons between it and Firefox - comparisons that Computerworld and others made this week - are unjustified, said Gavin.
"The net of all this is that any comparison of browser share adoption at this point is premature at best and misleading at worst," Gavin said. "In a few months, we'll be better placed to look at the share of the latest browser versions and get a sense for relative progress and adoption."
According to web metric company Net Applications, Firefox 4's average share for its first nine days was 3.2 percent, while IE9's in that same stretch was only 1.1 percent. On Wednesday, Firefox 4 passed the four percent share mark for the first time; the same day, IE9 stood at 1.4 percent.
It's not surprising that Firefox 4's share trumped IE9's. Unlike IE9, Mozilla's browser runs on Windows XP, Mac and Linux, operating systems that Microsoft's program doesn't support.
However, it was Microsoft's decision to support IE9 on only Windows Vista and Windows 7, versions which collectively account for slightly more than a third of all copies of Windows now in use. The company has said it did not want to develop for what it called the "lowest common denominator," the 10-year-old Windows XP, because, said Gavin two weeks ago, "That's not what developers need to move the web forward."
Gavin used that to make another point in his dispute with comparisons, arguing that since IE9 only runs on Vista and Windows 7 - and is especially targeted at the latter - its market share should be calculated solely on its use among Windows Vista and Windows 7 users.
"Adoption on Windows 7 is what we care about most," said Gavin. "Other browsers support other platforms, so if you want to draw comparisons you really need to take account of addressable base. With IE9, you essentially need to multiply by a factor of almost 3 to account for the difference in current addressable base."
Microsoft's made that case before, and in fact has gone so far as to claim that IE9 is the best browser for Windows because rivals "dilute" their energies on other operating systems.
Net Applications does not usually disclose granular data on its browser usage share numbers that would show how IE9 fares among Windows Vista and Windows 7 owners only, or how competitors like Firefox and Chrome match up on those operating systems.
The analytics company will release its March browser share data early Friday morning.