Keyword not provided

What do you mean by “Keyword not provided?”

Google is more likely to show “keyword not provided” when the search is not driven towards a particular keyword or intended to protect the privacy of the particular searcher. 

What is its impact on SEO?

Simply, it means that organic traffic for the search is no longer available. The keyword data wouldn’t be availed in Google Analytics. Thus, it can make it difficult to optimise content based on the actual search behaviour, i.e., keywords. As keywords are eliminated from the efforts of ranking, SEO experts are more likely to concentrate on the performance of landing pages, the intent of the user and topic clusters. These determine the success of SEO efforts as businesses may also struggle eventually with the phrase being shown for significant searches.