The increase in Mac share represents a gain of roughly 3.6 percent from December, when Apple's operating system reached its previous all-time high of 7.3 percent for all web views at the more than 40,000 websites tracked by the Internet firm.
The figure is also a 21.7 percent increase compared to the same period in January 2007, when Macs claimed 6.2 percent of site hits. By contrast, Microsoft shed two of its usage share points over the same period, falling from 93.3 percent at the opening of 2007 to 91.5 percent.
In the past, Net Applications has also cautioned that the existence of Boot Camp and Windows virtual machines for the Mac may also slightly distort the statistics, artificially inflating the number of Windows visits relative to actual systems bought with Windows pre-installed.
Use of Safari was also at its highest in January, just topping 5.8 percent compared to 5.6 percent the month before. It and Firefox continued to draw share away from Internet Explorer, which dropped from 76.1 percent to 75.5 percent of all browser use.
iPhone share grew slowly at 0.13 percent of all hits versus 0.12 a month prior. However, investigative work by Net Applications has shown that many of the missing iPhones unaccounted for by official carrier sales are scattered across the globe -- including in regions where few if any can afford the device.
"We've heard the rumors that many iPhones are being used outside the officially sanctioned countries," Net Applications says. "So, we decided to check it out and surprise, surprise, it's true. The iPhone has a presence in almost every country on Earth."
Surprisingly, a disproportionately large number of visitors come from Africa: as many as 2.2 percent phones come from Equatorial Guinea, while the Ivory Coast, Cameroon, and Senegal were also more likely than other, wealthier nations to be points of origin for iPhone web visits. Southern Asian countries as exotic as Brunei Darussalam also registered higher in the list than countries with easier access to the iPhone, such as Canada or Italy.
Countries at the bottom of the list include South Korea, whose networks are often technically incompatible with the iPhone, and longtime US political opponent Iran.