Use of Canonical URLs in Drupal to help SEO

When you have a block of content having multiple copies and living on multiple URLs you’re bringing down your SEO score. In such cases the search engines will select the “best” version if the content in search results. The rest of the copies will not only be filtered out but might even be dropped from search indexes.
Some of the problems the webmasters would face would include:

• Split Authority – According to the search engines web-authority is synonymous to the number of relevant link backs the site has. With multiple copies of the same content present out there, the links from other sites would get split, bringing down SEO score. All links pointing to the same singular page is considered safe.
• Irrelevant search results – You might not always have the desired results displayed on the search results page. The engines would often display the page of your blog having maximum link backs rather than the one having the most relevant content. This makes it hard for the user to locate the information he’s looking for and he hits the “back” button.
• The engines will use only so much bandwidth to crawl all pages in your site and the whole site might not get indexed. If the bandwidth is spent on indexing copies, pages with valuable information might be dropped out. That means you wouldn’t see those pages in search results.

Canonical URL
All major search engines including Google, Yahoo, Aol, MSN etc. now support a new tag called Canonical URL Tag. This new tag will allow you to specify which page you want the search engines to index and display when it needs to apply a filter.
This tag is nothing but a piece of code that you can place in the page header. Here’s the code
<link rel="canonical" href="http://yoursite.com/whatever-your-URL-looks-like"/>
Drupal users can install Joost deValk’s Canonical URL module and you can manage this information easily through the CMS. This however is only a patched version. We at Drupal USA offer the full version with our standard SEO package.

Having Canonical URLs doesn’t guarantee that the search engines will obey you, but they will consider your suggestion. It’s highly recommended to have Canonical URLs so that you hint the search engines to go in the right direction.