Apple's new Mac operating system ended October with an 11% user share of all Macs that went online during the month, the strongest start ever for an OS X upgrade.
According to Web analytics company Net Applications, Mavericks accounted for 10.9% of all versions of OS X used last month.
The California metrics firm's number corroborated similar data from ad network Chitika, which earlier in the week said that Mavericks had broken the 10% bar just five days after its Oct. 22 launch.
Mavericks' uptake pace was almost triple that of OS X Mountain Lion, the $20 upgrade Apple started selling on July 25, 2012. In its first seven days, Mountain Lion accumulated a 4% share of all Macs. Mavericks, however, had 10 days in its month of release.
It also had a huge advantage over Mountain Lion: Apple does not charge for Mavericks, and makes the upgrade available to users running editions as far back as 2009's Snow Leopard on Macs up to six years old.
Although the bulk of Mavericks' share came at the expense of Mountain Lion, which dropped 6 percentage points in October to end the month at 43%, Lion and Snow Leopard also dropped as some of those users upgraded.
The October user share declines of Lion and Snow Leopard were double the average of the preceding three months, a signal that the free upgrade tempted large numbers of users of each OS to abandon their older software. The Lion and Snow Leopard declines, however, were less than a third of Mountain Lion's.
Historically, people using the newest operating system -- whether Windows or OS X -- have been those who upgrade first and in the largest numbers.
Analysts have portrayed Mavericks' lack of a sticker price as part of Apple's long-standing strategy to give away software to encourage hardware purchases, where it makes its money. Other reasons they've cited have ranged from a reduction in OS X fragmentation -- which would let developers focus their efforts on the newest edition -- to a realization that the widespread practice of free operating system upgrades for mobile devices has become expected by consumers on their personal computers as well.
Some experts have also interpreted the move as a poke at Microsoft, which continues to make billions each quarter on sales of its Windows operating system.
Surprisingly, Apple has not trumpeted the number of Mavericks downloads, something it's regularly done with past OS X upgrades. Unfortunately, app analytics companies have no visibility into the number of downloads from the Mac App Store, and can only record the market's popularity rankings.
On that count, Mavericks has been the No. 1 free download, and the No. 1 overall, on the Mac App Store since its launch, said Marcos Sanchez, App Annie's head of corporate communications, in an interview Thursday. "By 3 p.m. on Oct. 22, Mavericks had shot up to the number one spot," said Sanchez. "It's been there since with a straight No. 1 ranking."
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com.