Although this feature has been around since 2009, we often get questions about what to do when there is duplicate or near-duplicate content on pages – specifically product pages of a site. The ideal solution is to have unique content on each of these pages, but when you have 20 pages for 20 different colors of the same shirt, creating this content can be time consuming and tedious. The next best solution is to add a canonical tag to the pages. A canonical format provides you with more control over the URL returned in search results. It also helps to make sure that properties such as link popularity are consolidated to your preferred version of the page (http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html).
There are 2 ways to attack this. The first option is if none of your content on any of the 20 pages is unique – say, for example, it’s all manufacturer created. In this case, you may consider putting the canonical in place to give those pages credit to the parent page (a shirts subcategory page, for example – assuming you have quality, unique content on that page). This is best used as a very temporary fix while you get unique content up on one of your product pages.
If your product pages all have unique content from other sites but similar to one another, you’ll want to use your analytics to determine the page with the highest SEO value for your site. Filter Traffic Sources > Sources > Search > Organic viewing: landing page, and then apply a filter to get only the 20 pages you’re looking to analyze on the screen. Typically, it’s pretty easy to tell which page has the highest SEO value – it’s safe to assume the page with the higher organic visits has the most visibility on the search engines and therefore the highest value. Other things to consider are the bounce rate: Google looks to the bounce rate of a page as a factor in deciding relevance and ranking – don’t canonical to a product page with an astronomical bounce rate. If you’re tracking conversions, you may choose a page that is a high revenue driver or has a good conversion rate (keeping in mind that a 50% conversion rate doesn’t mean much if only 4 people have ever visited
Once you have decided which page to point your canonical to, insert this snippet of code into the header of your page:
link rel=”canonical” href=”http://www.example.com/page-you-want-all-credit-pointed-to.html”
Canonicals are hints which Google honors strongly – use this to your advantage and reduce red signals on your site by implementing this simple tactic in your strategy.
For more in-depth information, visit Google’s webmaster blog: http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html