I’ve heard a lot of discussion recently on whether there is indeed a duplicate content penalty within the search engines, particularly Google. The short answer for me is yes, under some circumstances.
Some critics have pointed out that the duplicate content penalty is merely a myth and that a search engine such as Google wouldn’t have the horse power or inclination to check every page in its index against every other page for duplications.
However, if you try out a free service like CopyScape.com you’ll certainly see that the technology exists to scan for duplicate content within the Google index. Also, if you’ve followed the search engines for the past several years you’ll know that the search engines have employed penalties for mirrored sites and redirects (outside of the 301 redirects), which in my mind shows that the inclination to penalize duplicate content pages is there.
What is more convincing to me, however is my own personal experience resurrecting several customer web pages from search engine rankings oblivion over the past year. Simply by changing the text on a single web page that I knew was duplicated elsewhere would be enough to see dramatic results within days. These web pages I knew to be duplicated elsewhere either from my own searches or from the customer.
Earlier I stated that this duplicate content penalty applies only in some circumstances. The circumstances I am referring to are two web pages that are nearly identical textually. What I do know is that, for instance, my own homepage for my website has been pilfered by someone else (see CopyScape) but because there is other text on this pilfered page besides the entirety of my homepage it doesn’t seem to affect my rankings. So, it seems that a certain percentage (that I haven’t come up with yet) of duplicate to non-duplicate text is the threshold for the penalty.
Anyway, my conclusion is that a duplicate content penalty does apply for identical or nearly identical pages. However, its anyone’s guess as to what the threshold percentage is for duplicate versus non-duplicate text in order to avoid a duplicate content penalty between web pages.
