Decisive Visitors are Product Page Visitors who decide to Install (Direct Install) or leave (Direct Drop) without ever engaging with the page. In other words, these Visitors are only exposed to creatives that appear in the First Impression Frame (everything above the fold), and their first and only action is either tapping the install button or leaving the page altogether.
Before iOS 11, Decisive Visitors based their decision to drop or install with less information as App Preview Videos required engagement to view. With the new video autoplay mode in iOS 11, Decisive Visitors are exposed to much more content and can even watch an entire App Preview Video in autoplay before deciding to drop or install.
Decisive visitors represent 60% of all app store traffic.