Canonicalization & SEO : Should I use WWW or not?

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A Search Engine Journal reader wrote to ask :What’s preferable: www- version or non-www version? Are they the same? (Which version are people more likely to link to? Which one is ‘traditional’?)

We often come across websites that are accessible by both the www and the non-www version of its URL. While apparently both the URLs look the same, the search engines can treat them as separate sites altogether. This is something known as a canonical issue.

In one of his blog posts, Matt Cutts said:

“Canonicalization is the process of picking the best url when there are several choices, and it usually refers to home pages.”


Matt further adds:

“For example, most people would consider these the same urls:

* www.example.com

* example.com/

* www.example.com/index.html

* example.com/home.asp

But technically all of these urls are different. A web server could return completely different content for all the urls above. When Google “canonicalizes” a url, we try to pick the url that seems like the best representative from that set.”

Since the search engines treat the www and the non-www version of the same URL to be different websites, there’s a risk of duplicate content issues arising because of the same content served on both the URLs.

Search Engine Roundtable defines canonicalization as:

“choosing what single domain you want to use for your site, and what single URL should be used to request each of your pages, having urls that are outside this standard can cause problems in the search engines”

Besides that, if there are links pointing to both the www and the non-www version of a URL, the page rank and the link juice flowing in from all those links get split between the two URLs.

So now there arises a question, which one to choose and whether there is any ranking preference from the search engine perspective?

Regarding ranking preference, there is no such preference from any search engine. The search engines will rank whichever URL has the highest number of quality links pointing to it.

As far as choosing which URL to use in a website is concerned, we suggest the www version of the URL. This is because the www version has become a universally accepted standard for URL structures and because people are more likely to link to the www version instead of the non-www version (even if there is no www, people link this way out of habit).

But what if there are links pointing to both versions of the URL?

Just set up a server side 301 permanent redirection from one version to the other.

Matt says:

“Suppose you want your default url to be http://www.example.com/ . You can make your webserver so that if someone requests http://example.com/, it does a 301 (permanent) redirect to http://www.example.com/ . That helps Google know which url you prefer to be canonical. Adding a 301 redirect can be an especially good idea if your site changes often (e.g. dynamic content, a blog, etc.)”

Suggested Reading :

So, what are your thoughts on this www and non-www issue? Please feel free share your thoughts in the comments below.

Loren Baker
Loren Baker is the Founder of SEJ, an Advisor at Alpha Brand Media and runs Foundation Digital, a digital marketing strategy & development agency.
Loren Baker
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