Netcraft has been tracking Citrix NetScaler in the Web Server Survey for more than a year. In the latest survey, more than ten million sites were found using Citrix NetScaler.

Citrix bought NetScaler Inc. in 2005 for approximately $300M in cash and stock, acquiring an already maturing network appliance platform. NetScaler provides load balancing, an application firewall, and application acceleration to improve the performance and security of large web applications. NetScaler can run on a variety of dedicated hardware platforms, or it can be run as a server-based virtual appliance. BIG-IP is a competing product from F5 with similar features which reached 10 million sites back in May 2009.

1.71% of all websites found this month were served using the Citrix NetScaler platform; but within the top 100k busiest websites NetScaler’s share is much higher at 9.24%. The country distribution of the installed base has a few peculiarities: almost 30% of the websites hosted in Turkey and 20% of the websites hosted in Korea are using NetScaler. In Turkey, the blogcu.com network is using Citrix NetScaler and in Korea more than 50% of the co.cc subdomains were found to be using the platform. Worldwide, Microsoft, eBay, Weather.com, CNET, and MasterCard are among the busiest sites using Citrix NetScaler.