Microsoft’s web server is grabbing market share from the open source Apache, according to Netcraft’s August 2007 survey.

In November 2005, Apache was found on 71 percent of web sites, putting it more than 50 percentage points ahead of Microsoft IIS (20.2 percent). At the time, Apache’s market share advantage seemed insurmountable. But less than two years later, Microsoft has narrowed that 50 percent gap to 16.7 percent. The margin is even tighter in active sites, where Apache leads Microsoft by just 12.2 percent.

Note that even this 12.2% figure equates to about a 33% lead for Apache, so you can spin the figures one way or another according to preference. In addition, Netcraft now reports Google as a separate web server, accounting for 4.4% of sites, yet Google is running an adapted version of Apache as I understand it (Google Front End). It’s perhaps better to look at IIS in isolation. In August 2006 it had around 30% share, whereas today it has 34.2%, which is a significant increase.

How should we interpret these figures? It is difficult, and I would like to see a deeper analysis. I suspect that a significant factor is the move away from smaller ISPs which Netcraft identified in its June 2007 report:

This month’s data also yields some of the strongest evidence yet of the power shift in web hosting, with search portals and domain registrars experiencing enormous growth while paid hosting specialists lag behind. Microsoft (+532K) and Google (+521K) each gain more than half a million sites, while Go Daddy (+455K) and Demand Media (+245K) continue to amass huge numbers of users on their hosting platforms. This trend, along with the growth of social networks and image/video hosting services, is prompting deals in the hosting industry as providers seek the scale and breadth of services to compete.