05/22 By Dave Marquard

AdExchanger: With Two Sides To The Viewability Equation, Discrepancies Persist

Now that the MRC has defined that for a digital display ad to be viewable, half of the creative must be in view for at least one second, advertisers want to transact their media buys on the metric. Consumers, they argue, won’t convert if they never see an ad.

Publishers are also interested in transacting based on viewability. Advertisers now demand it, and many publishers hope advertisers will pay more for impressions that are in view.

Yet many wonder why discrepancies occur when the MRC definition seems so straightforward. Different vendors for advertisers and publishers often report different viewability rates. There are also time and location components to viewability: Advertisers are more effective at measuring the time aspect, while publishers are better suited to measuring the location of an ad. 

Discrepancies occur because viewability is often measured from one of two places: the advertiser’s ad server or the publisher’s ad server. Each implementation confronts limitations that affect measurement, which in turn, affect the reported viewability and measurement rates.

When viewability is measured on the buy side, the viewability solution sits with the advertiser’s ad server. Since the ad server is responsible for serving each and every creative, it’s very easy to know exactly when to start the viewability clock and determine when the creative is rendered for at least one full second.

But due to ad environment challenges, like unfriendly, cross-domain iFrames, advertisers can’t measure every ad unit in every environment, which means some percentage of ad impressions is simply unmeasurable. If a vendor reports that 60% of the ads were in view, with a 70% measured rate, what value do the remaining 30% have? The 70% rate must be extrapolated for the entire campaign, which can lead to confusion for both sides. 

Meanwhile, the publisher’s viewability solution is also integrated with its ad server. Since publishers are measuring fully owned inventory and not dealing with foreign ad environments, they have no difficulty determining whether the location of an ad unit is in view. Put another way, publishers can reliably determine the location of all ad units throughout their web properties virtually 100% of the time. 

What they can’t do, however, is measure the time an ad creative loads with the same level of certainty of advertiser-side technologies. Publishers know the exact moment an ad container loads, but that’s not the same as the actual creative, where rich media and video ads often take a longer time to render or start to play. I’ve seen discrepancies between times reach up to 20%. While 200 milliseconds may seem insignificant, when the goal is merely one second in view, it’s a huge difference, and one that will certainly have an impact on the overall viewability count.

Clearly, the current dual system of measuring viewability leaves too much room for disagreement and opens the door to mistrust. What’s needed is a measurement number that both sides can trust, and until that happens, transacting on viewability will be fraught with contention.