BrightHaus Digital Marketing Agency

Canonicalization – What is it?

February 14, 2013

There are few terms that cause as many raised eyebrows and confusion as the tongue twister that is canonicalization (seriously, try saying that three times fast). Mostly questions focus on, “what is that?” and “I’m sorry, can you say that again?”

But in reality, canonicalization is a very simple concept.

The main address to your website is known as your domain. Sometimes, that domain can be accessed via a variety of URLs. For example, and (note the lack of www. in the second example). If your website uses more than one variation of your URL, you need to choose a preferred URL to redirect all other variations to. This is canonicalization.

Canonicalization is important because it helps consolidate backlinking efforts. Without it, if half your backlinks are directed at and the other half at, then it makes it more difficult for search engines to recognize that all those backlinks are for the same domain. Also, it’s likely that search engines will recognize and as two different URLs with duplicate content, which can really stall SEO. When choosing a preferred URL, it is important to check your backlink history to see which variation of your domain is most prominent.

Google recommends several ways to canonicalize your URL, including:

  • Set your preferred domain
  • Use 301 redirects
  • Indicate your canonical (preferred) URLs by including them in a Sitemap
  • Specify a canonical link in your HTTP header

Any of these are good. All of them are better.

For more information, check out our What’s That? SEO Chat on the subject