Papering over the cracks with rel=canonical

  • 1
  • February 13, 2009
Patrick Altoft

Patrick Altoft

Director of Strategy

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?