“Visibility Score” is a summary metric that indicates your App’s overall discoverability inside App Store Search. It is the grand total of: Estimated volume of each keyword, multiplied by an accessibility factor corresponding to that keyword’s search rank.How do we compute “Accessibility” of a search rank position?
Accessibility is a weightage we apply to each search ranking in order to compute Visibility Score. The formula to compute the weightage is different depending on the screen size of a device:
For iPhone (iOS6), with 1 search result per page, we assume that each ranking position is only 90% as accessible as the position above it.
For iPad (iOS6), with 6 accessible Apps on every search results page, we assume that each search result page is only 90% as accessible as the search result page that preceded it.
For Android/Google Play, with 8 accessible Apps on every search results page, we assume that each search result page is only 95% as accessible as the search result page that preceded it.
It is possible that Visibility score does not change even if you change the keywords.
Visibility score is calculated based on volumes and accessibility (which is calculated by search ranking).