Canonical URL Tag Is Worth A Shot

The “Big 3″ search engines (Google, Yahoo and MSN) broke big news last week with the announcement they will support a Canonical URL tag to help webmasters (and search engines) better manage duplicate content issues. Duplicate content refers to identical or near-identical blocks of text on more than one page in a search engine’s index.

Examples of duplicate content on ecommerce sites:

  • A product is listed under multiple categories, each with its own URL
  • The search engine crawls a site and is issued a session ID. It indexes links with the session ID
  • A blogger copies a product link with a session ID or navigation tracking parameter like and unwittingly pastes the link as-is in a blog post
  • An affiliate link like gets crawled and indexed
  • Content is duplicated across sub-domains or sub-folders like or
  • The search engine crawls your print friendly version

Duplicate content problems include:

  • When multiple copies exist, search engines want to choose one version to show in search results and filter the rest. They may not show the version you want (print friendly or worse, an affiliate URL so you’re paying commissions on organic search conversions!)
  • Your SEO suffers because PageRank is diluted across several copies of a page (what is PageRank?)
  • Your site might not get fully crawled by the search engine as search engines will only give you so much attention in a given session

Duplicate content can also occur across domains, like multi-stores with country-specific domain extensions like or if many retailers are using stock manufacturer descriptions. The Canonical URL Tag does not remedy this situation.

Up until February, 2009, webmasters dealt with duplicate content by “sculpting PageRank” with rel=”nofollow” attributes, rel=”noindex” or using 301 permanent redirects. Now you can specify which is the original version of your content with the tag and rel=”canonical” attribute in a page’s head section, like:

<link rel="canonical" href=""/>

Which *should* nudge search engines in the right direction when choosing which URL to display.

I say *should* because search engines consider this a hint rather than a directive – much like my hairdresser, you can give your suggestion but it’s going to do whatever the heck it wants. Nevertheless, I believe this will help a lot of online retailers’ SEO efforts and reduce the headache of duplicate content.

Bonus if you got the “canon” and “shot” pun in the title, yes I know it’s kinda lame.

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15 Responses to “Canonical URL Tag Is Worth A Shot”

  1. I’m glad you explained the picture at the end ;-) Nice effort though!

    Plus a neat little summary of the new tag.


  2. Google, Yahoo and MSN are doing the right thing by managing duplicate content. This would not only help webmasters and search engines but it will help anyone who searches the web. It will also help make us find what we need with no trouble. You did an excellent job with the examples and explanations. This helped me understand what the three search engines are trying to do. Nice job on the post!

  3. This was the first I’d heard of this tag. I’ll definitely be doing more research on how to best implement this.

    Thanks for the great article on it.

  4. krishna says:

    I hope this Canonical url solves many issues for us. Nice initiative from the Search Engine world to take on duplicates

  5. Good news for the webmasters who are suffering with duplicate content issues. Mostly E-Commerce and Travel websites are facing canonical issues due to session ids. They all need to implement it right away for better results.

  6. Well explained – we have also given our thoughts on the canonical URL tag the following video:

  7. jamie keaney says:

    I think the canonical tag is a great secondary solution, although, as Cutts stated, you should just do it right the first time via your CMS, rewriting software, etc. I think retailers who do that will have more success over retailers who opt to use the canonical tag. Am anticipating the coming weeks to get feedback from the blogs on how this has worked from small sites to large ones.

  8. Yes, canonical link tag is worth to try. I have created a simple WordPress plugin to auto generate canonical link. Feel free to check it out.

  9. Brendon says:

    Hi Linda,
    I want to know if this would also solve having same page in http and https format?

  10. @Brendon

    http and https have their own unique purposes – I would suggest you block search engines completely from indexing https pages.

  11. sorry to somehow disagree but using canonical means a real problem in site structure so duplicated content. solve the problem, don¡t patch it:

  12. [...] as often breaking news from search engines get announced at these events, like support for the canonical URL tag. Because search engines are constantly working on improving their own tools and minimizing search [...]

  13. Great post, I never even realised this existed.

  14. Viagra says:

    This is a great innovation. I am going to try it right now and see what happens.

  15. John says:

    Great post and really well explained – there’s a lot of confusion around what exactly canonical URL tags are, and it’s not easy to write a straight forward explanation. Will bookmark this to say thanks!

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