The growth falloff varied by source, with one pegging it as the slowest rate since October, the second the most sluggish since November, and the third the most leisurely since December. All were in agreement, however, that Windows 10's growth was significantly smaller than in January, in some cases by just half as much.
Data published Tuesday by U.S.-based analytics vendor Net Applications said Windows 10 powered 14.2% of all Windows PCs in February, a 1.1-point increase from the month prior. Net Applications measures user share -- a proxy for the percentage of the global PC population running a particular operating system -- by tallying unique visitors to clients' websites.
Net Applications' Windows 10 growth for last month was just half of the 2.2-point increase of January, and barely beat the 1-point gain of December.
On the plus side, Windows 10's 14.2% user share put it ahead of the combined share of 2012's Windows 8 and its 2013 upgrade, Windows 8.1, for the first time in Net Applications' tracking.
Microsoft's latest OS powered approximately 213 million systems, according to Computerworld's calculations using Net Applications' numbers and Microsoft's oft-cited claim that 1.5 billion machines run a flavor of Windows. That would represent an increase of about 19 million in February, but would be significantly short of what Microsoft would likely tout, what with its assertion in early January that Windows 10 had been run on 200 million devices in the month prior.
Net Applications' data includes only personal computers, and omits other devices -- tablets, smartphones and video game consoles -- that Microsoft counts because they either run Windows 10 or a variant.
A second data source -- Ireland's StatCounter -- portrayed Windows 10's February growth almost identically.
StatCounter, which tracks global usage share -- a measure of activity rather than users, since it tallies web pages viewed -- pegged Windows 10 at 14.9% of all personal computers for February, a 1.2-point gain, or about 70% of the growth the month before. It was the smallest increase by StatCounter's measurement since November, when the firm tapped growth at just under 1.2 percentage points.
The third source, the Digital Analytics Program (DAP), also showed a slowing of growth for Windows 10 in February.
DAP collates visits to more than 4,000 websites on more than 400 different domains maintained by U.S. government agencies, so its data portrays a U.S.-centric audience.
According to DAP, Windows 10 gained 1.2 percentage points last month to end with 19.2% of all Windows PCs. The increase was half of January's, and the smallest since Computerworld started recording DAP's results in September.
In the grand scheme, a month's slowdown means little: Windows 10 has been, and will certainly continue to be, a success, if only because of the one-year free upgrade offer to consumers and many small businesses.
What was interesting about the growth slowdown was that it came during the month Microsoft said it had enabled automatic downloads of the Windows 10 upgrade to PCs running Windows 7 or Windows 8.1. That move, which had been announced in October, delivers the upgrade bits to eligible PCs via Windows Update, then initiates the installation process.
Microsoft has said that users could refuse the Windows 10 upgrade once installation begins, but has declined to say whether the upgrade starts in all cases, detail how the user authorization process plays out, and whether -- after a customer declines the upgrade -- it presents itself again later.
The assumption was that this would result in a major uptick in Windows 10's growth, but by the accounts of Net Applications, StatCounter and DAP, that hasn't yet happened.