SEO question: Should I use www or not?

On 01.26.10, In Seo, by NineSix

They say it is more a matter of style but it is important to note that search engines consider these two URLs to be different sites, which is true. You will only need to choose one of them for SEO purposes. But the question is: how should I structure my URL?

Let’s see. Here are some of feedbacks I’ve collected from several pro SEO bloggers:

Removal of the WWW can help streamline pagecode which can reduce data transfer and speed up page load times – natural search blog

Since the major search engines have been handling both types of URLs relatively consistently, I think it might be useful to use the No-WWW philosophy when you work on canonicalizing your WWW/No-WWW domain names. – natural search blog

However supporting www. for news sites is pretty much pointless and has no effect on usability as you have claimed because the site is going to go to your site whether they type in www or not so usability is a non-issue.

To start with, the http://yoursite.com is the true domain. The www version is technically a subdomain. From that perspective you should use the http://yoursite.com version. But…The use of www has dominated so successfully that it has become branded in our minds as the “proper” and perhaps, to many, the only prefix for a domain name. From a usability standpoint then this is probably the better choice despite adding four unnecessary characters to every one of your URLs. Trinity Sem

www and non www are both widely used. I feel that using www is important because most people know to put www before a domain name.

I sometimes think it’d be easier to drop the www. but to be honest people are likely to type it anyway.

The “www” subdomain is superfluous and unnecessary baggage on many URLs. Requests to a www subdomain should still work, but simply redirect to the main domain name and serve the appropriate content.

Why it matters?

Search engines treat them to be different sites. Searchers only want to see one version in results. And site owners worry that if search engines find multiple versions of a page, their link credit will be diluted and they’ll lose ranking.
Url canonicalization or picking preferred URL will also help increase your search engine rankings because search engine crawlers try to index and display the original or “canonical” version.

Which version is better to use?

If you are starting your site yet, both version should be fine as long as you pick either one of them. Chose what one you want to use and redirect the other.

For older sites, the best method is to do some SEO investigation and find out which version of the domain has the most backlinks and PageRank. Use the Google Toolbar, read the page rank bar for each version, and go with the one that shows more green.

When you are finish deciding which you one to use..

Make sure you do you redirect the other URL to your preferred URL. You can do it by using 301 redirects.
Change all your site links to your preferred URL.
Tell your preferred domain to Google by using their webmaster’s tool