Keyword density is a percentage devised from a simple ratio: the number of times keywords or keyword phrases appear on the page compared to the total amount of words. There are no hard-and-fast rules for what an optimal keyword density percentage would be, but it shouldn’t be too low or too high. A keyword density of 50%, for example, could be disastrous because then the content would be spammy and unreadable, leading to a bad user experience. On the other hand, a webmaster should know that the website is ranking for keywords, which keywords they are, and the keyword density. They may wish to adjust the density and monitor the effects on rankings.