WWW version is very useful to make your web site easily searchable by web crawler also WWW version helps to increase your chances make your web site rank higher in SEO purpose. One common use of URL Rewrite is redirecting http://domain.com to http://www.domain.com. Many people are doing this for search engine optimization (SEO) so that search engines only see the one site, rather than two sites. The goal is to set a permanent 301 redirect. URL Rewrite works at the global level, or site level (or application level for that matter). Where you apply it is really up to how you manage your server. Either will work for a domain name redirect like this. You can choose to create the rules using IIS Manager, or using a text editor and updating web.config directly. For specifying non-WWW version to WWW version for your web site in C#.net, write below code in web.config inside system.webServer tag,