The MMA encourages all of our members to become familiar with these guidelines, as the changes included will promote improved digital advertising measurement and better align all digital impressions with the viewability standard. The revised guidelines will shift both mobile in-app and mobile web from a “count-on-download” to a “count-on-begin-to-render” ad impression measurement standard. References to “served” impressions have been removed from the proposed guidelines, substituting them with the concept of counting event-driven impressions that allow for the “opportunity-to-see.” The update also expands the definition of mobile web, making clear that it is available through use of a mobile browser, as well as through browsing in an embedded app on a smartphone or tablet.