Papering over the cracks with rel=canonical

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  • February 13, 2009

The SEO world is alight this morning with the announcement that a new tag, rel=”canonical” will solve the problem websites and search engines have with duplicate content.

Basically if your URLs have additional parameters creating duplicate content you can now tell the engines which page is the canonical version without resorting to a 301 redirect.

So a page with session ID’s or affiliate ID’s such as:

Could include the rel=”canonical” tag to tell the engines the real version of the page:

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

Most people think this is a great idea but I’m not convinced. To start with nobody really knows how the engines will deal with this, will it work quite as well as a 301 redirect? Until we test it’s impossible to know for sure.

The URL Google gave as an example of a page which used the tag is still indexed although doesn’t rank in the search results which seems strange to me. It certainly isn’t behaving like a 301 redirect in that example.

Sounds great—can I see a live example?
Yes, helped us as a trusted tester. For example, you’ll notice that the source code on the URL specifies its rel=”canonical” as:

The two URLs are nearly identical to each other, except that Nelvana_Limited, the first URL, contains a brief message near its heading. It’s a good example of using this feature. With rel=”canonical”, properties of the two URLs are consolidated in our index and search results display’s intended version.

The main issue with this command is that any developers who are creating sites and content management systems with duplicate content and session ID’s are very unlikely to use the new tag in the correct manner. If people know that this sort of thing is a problem then they have most probably fixed it already and if they don’t know it’s an issue then they will never use the new command.

Everybody in the SEO world knows how to fix duplicate content issues so unless this actually reaches developers and CMS manufacturers it won’t help very much.

Clearly there are situations where a CMS can’t be fixed and in those circumstance the rel=canonical tag will be useful.

My advice is to keep doing things the right way and force the engines to index the right content, as soon as you give them a choice the potential arises for them to choose the wrong page.

When the search engines came out with sitemaps people thought it was a great way to get content indexed, what they failed to consider was that the content wasn’t being indexed for a reason. If a page has enough link juice to rank then it will be indexed, if it doesn’t have enough links to rank then forcing it to be indexed just means you have a page that’s in the index but doesn’t rank and what use is that?

Patrick Altoft

About Patrick Altoft

Patrick is the Director of Strategy at Branded3 and has spent the last 11 years working on the SEO strategies of some of the UK's largest brands. Patrick’s SEO knowledge and experience is highly regarded by many, and he’s regularly invited to speak at the world’s biggest search conferences and events.

  • Patrick Altoft

    Also this might be a big red “I’m an SEO trying to make my affiliate links pass PageRank flag”.

  • Pingback: Suchmaschinen führen rel=canonical ein | Frank the Tank()

  • Will Critchlow

    Can you use it across domains? Could be useful for syndication of content in that case…

    • Patrick Altoft

      No, you can’t use it across domains.

  • Frank the Tank

    I think you’re right. This rel-Tag fixes “self-inflicted” problems from my point of view. Lot’s of duplicate content is produce by bad cms-software.

    However: this rel-tag might be useful for session-urls (e.g. for web 1.0 online shops ;))

  • Ciaran

    Brilliant encapsulated what I’ve been trying (but failing) to express all morning.

  • Gaver

    I wonder if perhaps this is a bandaid for those without .htaccess permissions or capability.

    Trying to accomplish a redirect on a win platform is not an easy task when your a client on a farm and “one of many”.

    And even if you have access to .htaccess on a linux farm … the script to accomplish the redirect is not for the masses.


  • Pingback: Can you use rel = canonical to fix duplicate comment problems caused by comment pagination in wordpress? » malcolm coles()

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  • Zoya

    Hello Patrick,

    I have a website which is hosted by blogger, I am facing duplicate content issues. Can yuo please advice of anything that can be done to resolve this..

    According to google webmaster tools I have changed the keywords in the label and title which made it seem that they are duplicate but infact they were not.

    Can you please advice if using canonical in blogger will be of any help. Many Thanks


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