27th June, 2012

These URLs are all different:

  • www.essentialmarketer.com
  • essentialmarketer.com
  • www.essentialmarketer.com/
  • essentialmarketer.com/
  • www.essentialmarketer.com/index.html
  • essentialmarketer.com/index.html
  • www.essentialmarketer.com/Home.aspx
  • essentialmarketer.com/Home.aspx

Why is Canonicalisation important to SEO?

Canonicalisation problems are very important to SEO.  When a single piece of content – a paragraph or page appears in multiple locations on a site or even on a different site, this causes major problems for search engines in that they aren’t sure which page they should be returning for a particular search.  If you have duplicate content on the same site or the same content on a different site, this will be having a detrimental affect on your SEO and you should look to rectify this.

How to fix duplicate content issues

  • Change your Content Management System (CMS) to generate only the URLs you want. “Normalise” URLs
  • Pick one “canonical” URL and ensure you link consistently within your site
  • Make all the non-canonical URLs do a permanent (301) HTTP redirect to the canonical/preferred URL
  • Google’s Webmaster Tools: specify www vs. non-www
  • Break ties in Google by submitting your preferred URL in a sitemaps file

Tough Duplicate Content Issues

  • Sometimes can’t generate permanent/301 redirects
  • Can’t help how people link to you
  • Uppercase/lowercase paths
  • Session IDs
  • Tracking codes, analytics and landing pages
  • Sorting by ascending vs. descending
  • Breadcrumbs (the user’s previous web page)

Questions and Answers

Q: Does this work across domains?

A: No, only on the same domain

Q: Does this work across sub-domains/hosts?

A: Yes. So zeta.zappos.com could suggest www.zappos.com as a canonical URL

Q: Can I use this to suggest http://example.com be the canonical URL instead of https://example.com?

A: Yes, absolutely

Q: What’s the difference between this and a 301/permanent redirect?

A: They are very similar, but sometimes you don’t have the easy ability to generate 301/permanent HTTP redirects

Q: Do the pages have to be bit-for-bit identical?

A: No, but they should be similar. Slight differences are okay

Q: Can I use relative or absolute URLs?

A: Yes, but we highly suggest that you use absolute URLs. This is a powerful tool, and absolute urls leave less room for error

Q: Can you follow a chain of canonicals?

A: We may, but don’t count on it.  Point directly to the final URL.

Q: What if I point to a 404? Or have an infinite loop? Or I point to an uncrawled URL? Or www/non-www conflict?

A: Search engines will handle it as best they can.  Don’t cross the streams!


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