The keyword density checker tool helps with the measurement in percentage of the number of times a keyword or phrase appears compared to the total number of words on a web page. It can be used in the search engine optimization process to determine the relevance of a web page for a keyword or key phrase. It is important in terms of the position of a website in search results.
The optimal value of keyword density should be between 1-3%. It's even better if the URL, title, meta-description and HTML head tags contain that targeted keyword. For better rankings in search engines.