Our network classifies impressions into three main categories as defined by the MRC Viewable Ad Impression Measurement Guidelines produced by the IAB.
Any impression not identified as "visible" is still reported, however, it will not cost the advertiser nor earn revenue for publishers. This includes any vCPM placements or any clicks on a CPC campaign tied to a non-viewable impression.
Display - When an ad is served on the page, it is considered viewable if 50% or more of the pixels are visible for one second or more.
Content - Currently, content recommendation has no concept of a viewable impression and will be categorized as undetermined.
Video - When a video is played in-article or as pre-roll to other content, we will count it as viewable after it has been watched for 5 seconds.
Note: The concept of a “viewable/visible” impression was not live until April 12th, 2016. Any impressions prior to that date are considered “Undetermined” or “Unmeasurable”.
A non-viewable impression means that our system had the capability to track if the creative was seen or not, but received no indication that it was. For example, a creative could be rendered in the footer of a website but never viewed by the reader.
Due to technical limitations (i.e., ads loading in an iFrame or third-party ad server), we may be unable to track if a creative is visible or not. Our system will optimize for placements that are consistently untraceable and will prevent the delivery of vCPM campaigns to them. CPC campaigns however will still cost advertisers and earn revenue for publishers even if the visibility is unmeasurable.