A sudden spike of Windows' overall share led to increased user numbers for both Windows 10 and Windows 7.
Increases in Windows 7's share, Windows 10's, too, were more mirage than material last month.
According to California-based analytics company Net Applications, Windows 7 grew by half a percentage point to finish September with 22.8% of the global personal computer operating system share. However, when calculated as a portion of only Windows, that share climbed just one-tenth of a point, to 25.8%. This second number was the more important of the two, as it was a truer representation of Windows 7's path.
(Windows 7's percentage of only Windows PCs (the 25.8%) was larger than the percentage of all personal computers (the 22.8%), because Windows does not power every system. In September, Windows was the OS of 88.3% of the world's personal computers, up an amazing 1.3 percentage points from August. Of the remaining 11% and change, all but a tiny slice ran macOS, Linux or Chrome OS.)
The sudden spike of Windows' overall share meant that individual editions of Microsoft's OS had to also climb just to remain in place when calculated as a portion of Windows. What appeared as a significant gain in, say, Windows 7's share of all personal computer OSes was, in effect, nothing more than a minor advance in Windows 7's share of Windows because of the latter's upsurge.
Under normal conditions, if Windows 7 share goes up, Windows 10's share would almost certainly go down. Not in September. Windows 10's portion of all personal computers jumped seven-tenths of a percentage point to end September at 61.3%, a record for the five-year-old OS.
But to make it even more confusing, Windows 10 did slump, at least in the metric that counts. As a part of Windows only, Windows 10 fell two-tenths of a point, recording 69.4% for the month.
Forecasts for both Windows 7 and Windows 10 have been nudged by September's results, but not significantly disturbed.
Windows 7 still looks like it will slide under the 20% mark (of all Windows) in April 2021. And by August, the OS should be below 17%. (At the end of January — around the one-year anniversary of its retirement — Windows 7 will account for about 22% of all Windows.)
Computerworld's latest Windows 10 prognostication differs slightly from the one issued last month. By April, Windows 10 may account for more than 76% of all Windows, up over a point from the previous prediction. Come July 2021, however, Windows 10 should own 79% of Windows editions, a point less than the last forecast.
Elsewhere in Net Applications' numbers, Linux retreated for a second straight month, losing 1.2 points to fall to 1.5%. The latter was slightly more than Linux's March number, before its very uncharacteristic growth spurt started. The decline of the category, which lumps together all distributions, was the biggest factor in Windows' overall growth last month. (Share is a zero-sum game. Because the numbers must always total 100%, a decline in one OS must be accompanied by an increase in another.)
Meanwhile, macOS added another two-tenths of a point in September, pushing Apple's operating system to 9.7%, just a shade under the year's peak in April.
Net Applications calculates operating system share by detecting the agent strings of the browsers used to reach the websites of Net Applications' clients. The firm tallies visitor sessions of those browsers to measure global operating system activity.