How is viewability defined for an advertising impression?
Viewability defines an advertising impression as viewable when the ad meets set pixel and time thresholds, giving assurance of an opportunity to see it 1. Under the MRC guidelines, a display or video ad qualifies when at least 50% of the ad's pixels are in the viewable space of the browser for 1 or 2 continuous seconds respectively 1. Viewable impressions have become the currency for digital internet and mobile measurement, confirming the opportunity-to-see a digital advertisement beyond the fact that it was served 1.
What viewability does and does not establish
Viewability pertains to the availability of content, allowing the possibility of exposure 1. The definition should not be used to imply the presence of a user or that an ad has been viewed or seen, since viewable conditions can occur without a user present in digital auto-play, OTT and linear environments 1. IAB Europe describes an ad impression in the in-store context as the potential exposure of an individual to a particular advertising content play, understood as the opportunity to look at the screen 2.
Counting rules
- Each valid viewable impression originates from a valid impression, with a maximum one-to-one correspondence, so viewable impressions can never exceed rendered impressions on a campaign 1.
- An ad that qualifies is counted once within a user session, even if the user moves away and returns so it qualifies again 1.
- For out-of-home displays, the qualifying criteria are a functional display, presence in the display exposure zone, and a viewability condition existing 1.
A further refinement, LTS (Likelihood-To-See) impressions, applies an adjustment for the likelihood that individuals noticed the content or ad on the display 32.