What is TF-IDF?

TF-IDF (short for "term frequency — inverse document frequency") is used to to measure the importance of a given keyword on a page. Unlike keyword density, it doesn't just look at the number of times the term is used on the page; it also analyzes a larger set of pages and tries to determine how important this or that keyword is.

Say, in car repair, the term "tire repair" is likely more important than "turbocharged engine repair" — simply because every car has tires, and only a small number of cars have turbo engines. Because of that, the term "tire repair" is going to be used in a larger set of pages that speak about car repair. And this is exactly what the TF-IDF tool in WebSite Auditor will be able to catch! Looking at keyword usage stats of a large number of your competitors, the TF-IDF formula is going to show you:

1) Which keywords are the most important and relevant to your topic;

2) Which of them are used on your page properly (as much as search engines expect them to appear, since Google's known to use TF-IDF in indexing);

3) Which terms on your page are used too much or too little.