That’s WDF * IDF

Those of you interested and working in SEO may have attempted to search for more information on the ‘new’ text quality calculator, WDF IDF … and come up short. There has been surprisingly little information posted on the internet, unless you speak German in which case fill your boots.

So, why is this?


(© Creativa –

Well firstly, the idea has been pushed out by German, Karl Kratz, and promoted around SEO conferences across Germany, prompting german audience members to go home and blog about it – leaving those in the UK and US slightly in the dark. Karl is open to point out that this isn’t an original idea, in fact it seems the formula has been knocking around since the 70’s.

OK, So what exactly is it?

The acronym is for Within Document Frequency by Inverse Document Frequency. In short, it’s an algorithm that determines how relevant your article is for the Keywords that you’re optimising. It compares the term count to other values derives from the document count.

Isn’t that the same as Keyword Density?

No, it is (in theory at least) far more intuitive. Rather than just search your keyword, or even multiple keywords, it calculates other related terms that are being used frequently on high ranking document sites, and then orders these terms by their popularity weighting. The related terms, the semantic space between them and the popularity of the sites are then all compared against each other to provide accurate user data.

So how do I use WDF * IDF?

WDF IDF plug-ins or tools provide you with a list of terms to include in your article that will push it high up the search engine rankings. The data shows the top 10 sites using your keyword, and the top ten frequented terms and clearly compares the data to your own site. Tests have proven that by using the WDF IDF method, you minimise the need for excessive linking and raise awareness of your site by adding qualitative data, not just number crunching through the popular key words.

To clarify, you can’t just fill your article with repeated keywords. Text quality is taking into account in this algorithm and your site is directly compared against the highest competition. Your text needs to remain relevant, well defined and logical in order to compare with the top leaguers. Fortunately, the data provided from the formula enables you to easily do just that.