What is a viewable ad impression?
Impressions are considered viewable when they appear in the browser’s view and have been seen by a user. Industry standards for viewable ads are as follows: 50% of the ad has to be visible on the screen for at least 1 continuous second. For video ads, the viewability standard is that the ad must have at least had 50% visibility on screen, and must have been viewed for at least 2 seconds.