October was a big month for both Microsoft and Apple, which released new operating system versions: Windows 8.1 and OS X 10.9, respectively. It was Microsoft that saw the biggest impact, with Windows 8 losing market share for the first time, as users both upgraded to Windows 8.1 and went out to buy new PCs.

The latest market share data from Net Applications shows that October 2013 was a slow one for Windows 8 and Windows 8.1 combined, gaining 0.36 percentage points (from 8.89 percent to 9.25 percent). More specifically, Windows 8 fell 0.49 percentage points (from 8.02 percent to 7.49 percent), its first loss ever, while Windows 8.1 jumped 0.85 percentage points (from 0.87 percent to 1.72 percent).

At the same time, Windows 7 grabbed 0.03 percentage points (from 46.39 percent to 46.42 percent). Last month, Windows 7 gained more share than Windows 8 for the first time, but in October it remained flat.

os share october 2013 730x497 Windows 8 drops to 7.53% market share, falling for the first time as Windows 8.1 takes 1.72% share

Given that Windows 8.1 was released in the middle of last month, its gains are solid. OS X 10.9 was released later in the month, and it managed to hit 0.84 percent, passing OS X 10.4 and 10.5. November numbers will be much more interesting given that they will include a full month of Windows 8 and OS X users upgrading.

Windows 8, which saw its biggest gain in August at 2.01 percentage points, now has a new low month: losing 0.49 percentage points in October. It will likely continue to slip, given that all Windows users are being encouraged to get the latest and greatest.

The gains of Windows 8 and Windows 8.1 combined can be attributed to a minor drop for Windows Vista, which declined 0.35 percentage points (from 3.98 percent to 3.63 percent), and an even smaller one for Windows XP, which dropped 0.18 percentage points (from 31.42 percent to 31.24 percent). We’re still expecting it to fall below the 30 percent mark for the first time in years.

So far this year, Windows has lost share every month except for March and July. Between September and October, Windows lost 0.15 percentage points (from 90.81 percent to 90.66 percent). This loss was OS X’s gain: up 0.19 percentage points (to 7.73 percent). Linux dipped 0.04 percentage points (to 1.61 percent).

Net Applications uses data captured from 160 million unique visitors each month by monitoring some 40,000 websites for its clients. StatCounter is another popular service for watching market share moves; the company looks at 15 billion page views. To us, it makes more sense to keep track of users than of page views, but if you prefer the latter, the corresponding data is available here (Windows 8 is at 7.7 percent).

See also – IE11 takes off at 1.49% market share, Firefox gains a bit, but Chrome hits 27-month low

Top Image Credit: Robert Linder