Tom’s Simple SEO: What is canonicalization and how can it affect your SEO from Thomas Petty.

Have you ever heard of canonicalization? Maybe not. Technically, it’s a mathematical term, but what does math have to do with the search engines like Google?

Wikipedia defines canonicalization as:

In computer science, canonicalization (abbreviated c14n, where 14 represents the number of letters between the C and the N; also sometimes standardization or normalization) is a process for converting data that has more than one possible representation into a “standard”, “normal”, or canonical form.

Yeesh. You got that? Hm, me neither. Cononicalization in a general sense, just means that there are many paths to get to the same result (sounds kind of zen). In a website, it means there are many URLs (web addresses) that lead to the same result or page of content. This doesn’t mean links – it means web addresses.

For instance, if your website address is http://www.examplesite.com, and http://examplesite.com also works (and doesn’t change to the www version), then you have two URLs that lead to the same physical page of content. No big deal, right?

Actually it is a big deal. Google counts each URL as a unique page of content. If two web addresses resolve to the same page or content, it’s two physical addresses that both work, and therefore you may have a duplicate content issue. You see, Google and the other search engines don’t like duplicated stuff. It’s considered to be a “cheat” to get multiple pages through different URls listed, and therefore degrades the value of the secondary duplicate.

Now what happens if http://www.examplesite.com/index.html also works, and doesn’t change back to the root version? Same thing. Now you have three URLs pointing to the same content. Oh but wait, that then means that http://examplesite.com/index.html also works! Now you have four versions of URLs all pointing to the same page! It’s also probably going to work on each of your subpages, so you’ve got dupes all over the place. Yuck.

Four Kinds of Canonicalization (Generally Speaking)

Most of the common canonicalization issues we see include the following types (alhough there are more):

  • Internal Structure
  • Content Management Systems (CMS)
  • Search Page Results (on your website)
  • Multiple Domain Names

Watch the video to see if your website has any of the same issues.

Comment and tell us about what you found on your own site.