Canonical Link Rel vs 301 Redirects: Using Canonical Link Rel tag for SEO purposes

Back in February, Google announced their support of the Canonical Link Rel element, and it was also announced that Yahoo! and MSN would soon follow suit.  If you’re not familiar with it, think of the Canonical Link Rel element in terms of a 301 redirect–you can tell the search engines to ‘focus’ (though in this case, there’s no redirect) on a page you specify.  It is placed within the head tags of a web page, and is a great remedy for the duplicate content stigma.

Essentially it looks like this:

<link rel=”canonical” href=”http://www.seoracle.com/” />

** This needs to be placed below the <head> tag but above the </head> tag.

By specifying which URL you consider to be “right,” Google and other supporting search engines will now credit all inbound links to that one URL.  Here are some examples of how this is useful:

WWW vs Non-WWW

Having a working www and non-www version of your site means the search engines may see your site ‘twice.’  There may be danger of duplicate content here.  Furthermore, if you have 10 inbound links pointing to one, and 10 pointing to the other one, this link equity will be split, and neither version will benefit from the 20 inbound links.

For example;

yourdomain.com
www.yourdomain.com

Assuming the 2nd domain is your preferred version, you would use:

<link rel=”canonical” href=”http://www.yourdomain.com/” />

Default or Index pages

This problem can be similar to the one above.  Many sites have inbound links pointing to just their domain name, whereas their site’s internal links point to something like /default.aspx.  This creates homepage confusion.

www.yourdomain.com
www.yourdomain.com/default.aspx

Assuming the 1st URL is your preferred version, you would use:

<link rel=”canonical” href=”http://www.yourdomain.com/” />

Dynamic URLs

This problem often occurs when you implement URL rewrites.  Your site will have both the original version of the URL in addition to the rewritten version.

www.yourdomain.com/blue-widgets/aqua-blue-widgets.aspx
www.yourdomain.com/default.aspx?cat=2&subcat=3
www.yourdomain.com/blue-widgets/aqua-blue-widgets.aspx?cat=2&subcat=3

Assuming the 1st URL is your preferred version, you would use:

<link rel=”canonical” href=”http://www.yourdomain.com/blue-widgets/aqua-blue-widgets.aspx” />

Domain Name A to Domain Name B

When I originally wrote this post, Canonical Link Rel element  was not supported for cross-domain referencing.  This is no longer the case.  Simply add the element the same way you would another page on the same site, using the entire URL path.

Canonical Link Rel  vs 301 Redirects

In many of these situations, a 301 redirect will be the ideal solution.  However, sometimes a 301 redirect isn’t so easy.  If you’re using classic ASP and don’t really have access to the IIS server for the website, 301 redirecting the non-www version of the site to the www version may not be possible.   Even when it is, this often necessitates a higher level programmer, which most SEOs aren’t.

Then there’s the issue of time constraints.  Anyone who works in a fast-paced internet environment knows that even if you do have an impressive team of inhouse developers, they are often busy putting out fires or developing other new features.  A  Canonical Link Rel tag can serve as a great quick fix.

One instance where you want to use the canonical link rel element instead of a 301 redirect is in instances where you have duplicate content and you don’t mind the extra content out there.  For example, you may have two websites with overlapping products or information (for example, you may have two e-commerce sites that have a slight overlap in products) or multiple pages within a site that have the same content (for example, the “printable” version of an article).  In the first instance you’d of course, want to modify some of your content on one domain so as to not leave them as duplicates.  But in the meantime, you can make sure your pages aren’t being regarded as duplicate content by the search engines.

So the Canonical Link Rel element is no replacement for the 301 redirect.  In many situations you will probably find yourself having to use both.

Source for further reading

Comments (6)

  1. Will says:

    I have set my canonical up without the trailing slash /.

    So it looks like this…

    and not this….

    Is this incorrect?

    Will

  2. Will says:

    Sorry my html was striped out last time….

    I have set my canonical up without the trailing slash /.

    So it looks like this…

    link rel=”canonical” href=”http://www.yourdomain.com”

    and not this….

    link rel=”canonical” href=”http://www.yourdomain.com/”

    Is this incorrect?

    Will

  3. admin says:

    Hi Will,

    I personally prefer using the trailing slash. But as long as you’re condensing the link juice to one version (in this case, with the canonical link rel element), it shouldn’t matter which one you choose.

  4. Alejandro León says:

    Seems your Domain Name A to Domain Name B statement needs to be updated. Now it is possible (at least for Google):
    http://googlewebmastercentral.blogspot.com/2009/12/handling-legitimate-cross-domain.html

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