Have you ever found yourself providing links to affiliates or other link partners, stopping momentarily while you create your link URL to think, “Should I include the www. before my domain name, or should I leave that part off? Does it even matter for search engine optimization?” The short answer is yes, it does matter. The long answer is a matter of consistency. If you’re going to use the domain name without the Worldwide Web prefix, you need to be consistent. The same thing applies if you want to market your domain name with www included.
Here’s the rationale. Search engines see each version of your domain (with www and without) as separate domains. For instance, http://www.mywebsite.com/ and http://mywebsite.com are viewed as different URL’s, even though they really point to the same page. If you are busy spending time getting links to your site (as most SEO people are), your efforts would be best served by having your link partners be consistent in the way they link to your site. The same goes for your internal links. You need to be consistent in your use of links.
The need to be consistent with how you link to your website and within your website involves two SEO concepts. The first is duplicate content. The second is link juice.
Much has been made in the SEO world about duplicate content. Duplicate content refers to the same information (specifically identical or nearly identical blocks of text) showing up in more than one place on the web. Search engines prefer not to show more than one copy of the same thing in their search results. Within the past few years, Google has specifically told webmasters that its algorithm is configured, when it encounters perceived duplicate content, to find the best (likely the original author) source for the content and retrieve and display that source in search results.
Linking to pages on a website using more than version of your domain essentially splits your website, causing search engines to think that the content exists twice. For instance, if you link to http://www.mywebsite.com/article.html as well as to http://mywebsite.com/article.html, search engines will see article twice, once with the www domain, and once without.
Google has clarified that duplicate content cases are normally nothing more than situations in which their algorithm has to figure out which source of the content is the best to display. In less innocuous instances, Google has warned that spammers who use duplicate content heavily will be severely penalized. Inconsistency with linking to www and non-www versions of your website won’t get you penalized because of duplicate content. However, there are some guidelines Google has provided for steering clear of problems with duplicate content caused by having links to more than one representation of your home page.
Google allows you, through Site Configuration ->Settings in your Google Webmasters tools account, to tell them which way you prefer for them to refer to your domain, with or without www. In addition to telling them your preference, they advise that you redirect any requests that don’t use your preferred method. For instance, if you tell Google you want your domain to be referred to using http://mywebsite.com, then you should check to make sure all internal (and as many external as possible) links that go to http://www.mywebsite.com are redirected, using 301 directs, to http://mywebsite.com.
Getting links to your site is one of the most important parts of search engine optimization, especially SEO for Google, which places a lot of weight in its search algorithm on links coming to a site from external sources.
If you are getting links to your site using both the naked domain (without www) and the www version of your domain, it would be wise to choose one of those versions and publicize it when seeking link partners. PageRank, Google’s measure of the importance of your webpage, is determined by the quality and quantity of links pointing to it from other webpages. Webmasters pride themselves in their home page’s PageRank, using it as an important indicator of their site’s value. Simply put, if site’s linking to yours (as well as pages in your site that link internally) don’t use a standard for linking to your website, you’re PageRank will suffer when compared with a situation in which inbound links to your website all use the same version of your domain.
Depending upon the strategies you have for getting links to your website, you may have varying levels of control of how others link to your site. At the very least, you can manipulate the internal links on your site. When working on link building, I have a standard format (using my non-www domain, which I’ve told Google I prefer) that I publish for linking to my site.
Even with a published standard method for linking to your website, you have limited control over what people actually use. For those cases where you get links coming in to your non-preferred format, you can set up server-side 301 redirects which will forward incoming links to your preferred domain. Your web host can help you set up server-side 301 redirects if you don’t know how.
The main point of this discussion is that, for SEO purposes, it’s best to set up your linking network to link to one version of your domain name, whether you choose to have www in front or not. Doing so will reduce any confusion search engines may see when they follow links to your site, and it will improve your Google PageRank.