Overview: Cannibalization occurs when the content on different pages of a website targets the same keyword within a search engine optimization campaign. The cannibalized keyword may not be the focus of a given page, but its prominence on other pages, however accidental, may cause confusion for the search engine in determining which page is most about the given keyword.
How it works: To best understand this concept, imagine you are working with an e-commerce site selling car parts. On the homepage, you might target the keywords car parts, buy car parts, and/or some slightly more long-tail keyword, such as European car parts. You might also include in the title tag of the homepage, as well as in some of the homepage’s copy, information about parts for different makes (and ultimately the corresponding keywords) such as BMW parts and Honda parts. If your site is well organized, you likely have pages dedicated to these particular makes, and for their corresponding keywords (BMW parts, Audi Parts).
Now, if you have one page that is dedicated to targeting the keyword [BMW Parts], and you have enough content about “BMW parts” on your homepage, you are cannibalizing the keyword “BMW parts” because you have confused the search engine as to which page is the best result for someone searching [BMW parts.]
Solution: The only real solution is to keep each page focused on one particular keyword. Remember, search traffic will enter your site through many pages other than the homepage. Keep the homepage focused only on the most general keyword(s) and have an appropriate information hierarchy that matches your website’s information with the site’s architecture. If necessary, add new landing pages!