Search engines use keyword density to determine the relevance of a Web page to a key word search. Keyword density refers to the percentage of times keywords are used within the total indexable words on a Web page. For example, if a keyword occurs three times on a Web page with 100 words, then the keyword density is 3%.

While each search engine's preferred keyword density differs, it is best practice to make sure it is high enough for the keyword(s) to stand out as a major topic of the page. Use caution not to overuse a keyword(s) as overuse can sometimes be perceived as spamming.