Within 36 hours of its release 21.8 percent of iOS users it tracks downloaded the upgrade, a record for the quickest adoption rate of any iOS version, Onswipe said.
Among the iOS users tracked by Onswipe, 24 percent were iPhone owners and 21 percent iPad owners, CNET reported Thursday.
Onswipe offers customers tools to create Web sites designed to be viewed on mobile devices and as such its platform tracks 13 million active iOS users, up from 10 million last month.
While just a portion of the total of iOS users, the Onswipe numbers provide a good measure of the adoption rate of iOS 6.1, CNET said.
The previous version, iOS 6, reportedly reached nearly 300 million iPhone, iPad and iPod touch users just five months after its release.