Canonical Tags
Posted on 27. Feb, 2009 by in basic SEO
There’s a lot of duplicate content out there, some generated for heinous purposes, and others not. One not so heinous form of duplicate content occurs when you have two different URLs pointing to the same page. For example, www.gajshost.com and gajshost.com. Matt Cutts initially lists the different ways you can solve this duplicate content problem:
- use a 301 redirect
- set preferences in Google Webmaster Tools
- set your content management system (e.g Wordpress, Joomla) to generate only the form of URL that you require
- submit a sitemap (Google takes the URLs listed as a clue about which ones to use)
The reason that Matt is talking so quietly in this video is that they’d only just got Amy off to sleep and they didn’t want to wake her.
However, these methods may not be available to some web publishers. In this video, Matt Cutts tells of an agreement between Google, Yahoo and Microsoft to support the use of a new page level tag. The new tag is placed by the webmaster on the duplicate page (i.e. the page that should be omitted from Google’s index) and it refers to the preferred (the canonical) version of the URL. Behind the scenes, the big 3 search engines treat the presence of this tag like they would a permanent 301 redirect. Therefore, all PR and SEO benefit from backlinks to the page with the tag get transferred to the page referred to in the tag.
Hijacking
Before you ask, no you can’t. This tag only works within your domain or subdomain. Matt is quick to point out that you can’t do any 301 hijacking.
How To Use The Canonical Tag
You can read it from the horse’s mouth. Or you can trust me. Add a link tag with the following format to the page that is a duplicate of your preferred one:
<link rel="canonical" href="http://www.yourdomain.com/your-preferred-url" />
The tag should be placed within the <head> section.
I was going to refer to the new tag as a directive earlier but it’s a good job I didn’t. Because it’s not. Google state that it’s more a hint that is honoured strongly.
