What is keyword density? Keyword density is expressed as a percentage. It is based on the amount of times your keyword or keyword phrase appears on the page in proportion to the other words on the page. Each of the major search engines have built in the importance of keyword density in their search algorithm. However, the importance and ranking of the algorithm is different with each search engine. Also, each engine has its own policy as to when to penalize for too high a keyword density rating. At this point, you’re considered a spammer.