Google Webmaster Tools announced on October 31, that webmasters will be alerted to the existence of duplicate content across domains via messages in their accounts. Dupe content can happen many ways, and these days, it’s SEO Smart to have a handle on it, especially when it occurs on two or more sites that you own.
Image by Frederick Md Publicity via Flickr
For example, you may have the same site in various languages. You know what they say about honey badger, right? Google’s rather like him in that Google doesn’t give a sh*t. Their algorithm will see the dupe content, in whatever language you want to present it, tag it dupe and nix it from the index. They will show only ONE page and serve the one that seems to fit the query best, unless you specify which page you want to be shown as the canonical page.
Or, if you have content that you no longer use on one domain that you’ve moved to another, be sure to use a 301 redirect to let Google know that the content has been moved. This can be for whole websites or just for single pages.
For example, when moving your website to a new domain, it’s important to use Webmaster tools to alert Google of the change and then, to 301 redirect your old site to your new one. Otherwise, traffic and ranking juice could very well still be going to the old site instead of the new and it will be shown rather than the site you intend. Google is smart, but like honey badger, it operates on instinct.
A canonical tag is like this, and you would add it to the <head> section of all non-canonical pages (those that are duplicate and that you don’t want indexed):
<link rel=”canonical” href=”http://www.domain.com/page1.html” />
The tag tells Google that you want http://www.domain.com/page1.html indexed and not http://domain.com/page2.html, where the duplicate content lives. This link should be placed on page2.
Anyway, where this is really important is when you are selling products on an ecommerce site, for example. If you have the same product and description in multiple categories, use rel=”canonical” on the pages that don’t matter as much. Just choose one page to be shown, and the others should have the tag added. Otherwise, having duplicate content on your website could really cause problems with where you show up in search.
