Google is busy crawling your websites with and without a www and recording them as 2 separate sites. This is duplicating content is affecting your pagerank and search engine rankings by the way Google crawls your website links. These are a type of Canonical domains and it is all about adding a www or not…
For example, you can access our site from both
A CNAME record or canonical name record makes one domain name an alias of another.
Google Sitemaps has an easy option that lets you set a preferred domain name which can be with or without a www. This will help in consolidating these listings so that Google can more accurately determine your site’s PageRank. Though your site will be updated in the Google search results over a period of time, this information will be used for all future crawls of your site and indexing refreshes. Remember that this feature is available for root sites only and not supported for subdomains or subdirectory sites.
I know many webmasters who use the 301 redirect to point the non-www versions of their site to the www version. Probably such users might not find much benefit of this feature as they are already redirecting the non-www page to the www page in a search engine friendly way. While a 301 redirect will affect your results on all search engines, this Google Sitemaps fix will affect Google results only. Such 301 redirects help fix all your permalinks, helps visitors link to your preferred domain name and is good for search engine optimization. See how to set 301 redirects. You can use the Permalink Redirect WordPress Plugin for fix this issue in WordPress.
Even google does it. Type google.com in your web browser.. what happens… it gets redirected to www.google.com
Set the preferred canonical domain name in Google Sitemaps. Help Google consolidate the links to your site and direct the Googlebot crawl to the preferred version of your pages.