Our scroll depth tracker measures the amount of the page a reader has seen, with the top of the page defined as 0% and the bottom of the article (not including footer) as 100%.
As a user scrolls down the page, multiple tracking events are fired at each 10% interval in order to capture the maximum depth viewed. These events automatically account for screen width and magnification.
For example, in the diagram below, the tracker would register a 50% scroll depth.
Our aggregate scroll depth data allows editors to understand how much of a page their readers typically see, and therefore provide a guide as to where to place a CTA or interactive sidebar.
Going forward, we hope to integrate scroll depth into our understanding of Engagement and augment our current metrics (like Engagement Time) with scroll behavior.