If you don’t already know what DC (Duplicate Content) is, please go Google it. Short described, the problem is that pages can be accessed from several URL’s, and the Search Engines don’t know which page is the original. This is a big problem for several reasons:
- Your “linkjuice” / PageRank-flow is spreading to different pages.
- The Search engines will treat each page as individual and index them as different pages
- In worst case scenario you will get punished and get lower rankings
Duplicate content can be of many variations. Here is a couple of examples:
- www.domain.com and domain.com(could be ANY subdomain like server2.domain.com)
- domain.com/page1 and domain.com/page1/(The trailing slash in the end WILL be seen as different page)
- domain.com/index.php and domain.com/
Luckily for developers, there is many easy ways to fix this. Lately my favourite has been using canonical tags, but you have to be careful with those. 301 redirection is in many cases the best option, and is a MUST if you already have DC problems.
By implementing canonical tag with the full url (fx “http://domain.com/page1”), Google knows that it is the original page, and will stop thinking /page1/ or /page1/?x=y is different pages. But be careful: just a couple of weeks ago, I pushed an update to a site with large amounts of dynamic content. I didn’t notice that I forgot “http://” in my canonical tags, and suddenly I had over 30.000 404 errors in Webmaster Tools, because Google couldn’t find “http://domain.com/domain.com/url”.
Now when shit happens, like in the case above, 301 Redirects is the absolute best way to go. This will pass pagerank on to the original page and redirect both visitors and the crawlers.
So to sum up about Duplicate Content: avoid it. Before it goes wrong. Make sure that all subdomains 301 redirect to your original (or www-version if you use that) – or that you at least have canonical tags implemented. Also make sure to decide if your URL’s should be shown as /content, /content/, /content.html or whatever you prefer. If you do not implement these things your site will most likely get punished. If your competitor is of “evil mind”, and see that you show the same content on all subdomains without canonical tags (common mistake) he can linkbuild to your different URL’s and get your site punished for DC.
(suddenly you might see “looser.domain.com”, “imanass.domain.com” and whatever ranking instead of your original page – that wouldn’t be fun, would it? And worst case scenario, get de-ranking and even de-indexed as punishment for Duplicate Content)
What is your experience with Duplicate Content as a web developer? Do you implement and use 301 Redirects & canonical tags in your projects right from the start? Be sure to leave a comment, and feel free to come with more tips and corrections.
This is part 1 of 5 in my series of Must-Know SEO for Developers. You can find all the parts here.
