The WordPress canonical link plugin has been succeeded (and in many ways superseded) by my new WordPress SEO plugin. Below follows an explanation of what a good canonical link element does and why it’s important to your site’s SEO.
Suppose you have read my Twitter Analytics post. You’ve started tagging all the URL’s you spread on Twitter with Google Analytics campaign variables. At some point, a search engine would enter your site through this URL:
If it did, in “old times”, this would mean you’d have a duplicate content issue: the same content indexed under two different URL’s. An issue SEO’s have been trying to solve on web pages for ages, which sometimes created huge limitations. This is where the canonical link element, and thus also my WordPress SEO plugin, comes in.
The plugin would in this case add this code to the
<head> section of your page:
<link rel="canonical" href="http://yoast.com/twitter/analytics/"/>
Now the search engine will count the links it has seen to that campaign tagged URL, towards the canonical URL. It will no longer index the campaign tagged URL. Simple, yet effective. Please bear in mind it will still crawl the non-canonical page, as it has to to find the canonical.
As you can imagine this would also prevent issues with, for instance
Using the right canonical link
It is very important that your canonical link element is exactly correct. Some older canonical link plugins for WordPress, including my own, had a wrong canonical link element for the homepage at times, and unfortunately this is still wrong in All In One SEO Pack. This could lead to indexation problems or to a search engine no longer using your canonical link element, which would be a shame.
The canonical link element works with Google, Bing and Yahoo! and is therefor a very powerful tool to have in your SEO arsenal.