What is meant by this?

In WDF*IDF, the abbreviation WDF stands for "Within document frequency", while IDF stands for "Inverse document frequency". The WDF IDF value is a formula that checks and evaluates textual content for its relevance in relation to content from other websites.

Here, the WDF stands for the analysis of the frequency of a keyword in relation to all other keywords within a document and classifies them according to their weighting. From this, the relevance of the content is determined.


WDFi= log2(Freqi,j+ 1) / log2(L)

i = keyword

j = document

L= number of words in the document

Freq (i,j)= Frequency of the keyword i in the document j

The IDF is used to calculate the frequency of a keyword in the content in relation to the frequency of keywords within other documents. In other words, the keyword density.


IDFt= log (1 + ND/ ft)

ND = Number of all documents checked

ft = number of checked documents containing the term t.

If you then multiply both factors, this gives you the weighting of the term in relation to all other possible documents that use the same keyword.


While people used to check the text for keyword density, i.e. the frequency of the keyword in relation to the overall text, they have moved on to using this analysis formula. It provides much more information about the value of a content in the overall context.

What is its importance for search engine optimization?

Search engines like Google rate a relevant and for the customers written text very high. As part of the OnPage optimization in the SEO with the help of this formula you are better able to create a semantically good and unique content, which has a very positive effect on the ranking in the search engines. With WDF*IDF analysis you can significantly increase the web presence of your own textual content.

What are the disadvantages?

This formula is not the beginning nor the end of an optimized text. You should not create your content according to the formula's word curve, because it is only a purely mathematical formula that does not take into account some things like synonyms or the distribution of terms that are related to semantics of the whole text. Likewise, it does not take into account targeting and readability, which is enormously important in terms of user-friendliness.

It is important to consider this formula only as an aid to content creation.

WDF*IDF and online stores?

For online stores, it is not recommended to use this formula, because in online stores the descriptions of the individual products are in the foreground. The use of this formula makes little sense here, because the WDF*IDF takes into account the content of the entire page. What is the use of a content manager who writes a product description of a bicycle saddle and gets suggestions for optimization, which has a reference to oil for bicycle chains.

What analysis SEO tools are available?

Here are recommended:

  • Semrush
  • Xovi
  • Seobility
  • Ryte
  • Searchmetrix
  • Sistrix

As content and SEO Agency in Munich we understand how to create excellent and optimized content.

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