The 3% represented approximately 45 million systems.
User share, the percentage of all devices online during a period that ran a specific operating system, reached 2.7% of all personal computers the week of Aug. 2-8, according to data provided by Net Applications. Windows 10's user share of those systems running one form or another of Windows was 3% that same week. (The two numbers don't match because Windows overall had a user share of 90.7%, not 100%; other operating systems, including Apple's OS X and the open-source Linux, make up the remainder.)
The latest user share number from Net Applications was dramatically higher than the week of July 26-Aug. 1, the stretch during which Microsoft launched Windows 10, first to its Insider testers, then to a wider audience of customers who had "reserved" a copy from their Windows 7 or Windows 8.1 machines.
For launch week, Windows 10's user share of all Windows devices was 1.2%, reflecting Microsoft's slow ramp towards broader distribution.
The week before launch, July 19-25, Windows 10's user share of all Windows systems was a minuscule 0.4%.
Windows 10's climb came largely at the expense of Windows 8.1, which during the same three-week stretch fell from 13.7% of all Windows devices to 11.9%, representing a 13% decline. Other editions of Windows fell less markedly: Windows 7, for instance, dropped 1.5 percentage points, for a fall-off of about 3%.
Those reductions were in line with forecasts, which predicted that the first to move to Windows 10 would be Windows 8.1 users, while Windows 7 device owners would be slower off the mark because they have less to gain from an immediate upgrade to an edition whose biggest visible change was the restoration of the Start menu.
Windows 10's user share was in line with Windows 7's during its first few weeks of availability in the fall of 2009, and dramatically larger than Windows 8's three years later. By Net Applications' historical data, Windows 8 did not reach the 3% milestone until the end February 2013, four full months after that edition's debut.
Notable in Net Applications' numbers was the implication that tens of millions of users now run Windows 10.
With an estimated 1.5 billion Windows devices worldwide -- a figure that Microsoft has repeatedly touted -- the 3% attributed to Windows 10 represents more than 45 million systems. The week prior, when Windows 10 was available to a smaller number of Windows users, Windows 10's 1.2% represented approximately 17 million machines.
Although extrapolating numbers in this way results in only the roughest estimates, they came close to matching what Microsoft was saying before Windows 10's July 29 launch: Then, the Redmond, Wash. company trumpeted 5 million Insiders running the preview. According to Net Applications, about 6.3 million Windows systems relied on Windows 10 the week of July 19-25.
Net Applications measures operating system user share by tracking unique visitors to the websites which use its analytics platform.