In the digital world, an impression means only that the ad was served and loaded on a webpage, not that it was necessarily viewed - or viewable. If the ad is served below the fold and the user does not scroll down to bring the ad into view, or if the user minimizes their browser, opens a new tab, or in any other way obstructs the ad, then it is never seen. The Interactive Advertising Bureau (IAB) considers a banner ad viewable if 50% of its pixels are on-screen for just 1 second. For video, 2 seconds. And for large display units, only 30% of the pixels must be in view. Some might consider that bar to be pretty low. The minimum requirement for viewability is not necessarily the minimum requirement for a consumer to actually digest and understand the advertisers’ message. But advertisers are only ever paying for the opportunity for their ad to be consumed. We can’t guarantee that all paid digital impressions are properly digested any more than we can guarantee radio listeners aren’t turning down the dials during commercial breaks, or TV watchers aren’t leaving the room. The least that we can do, now, is measure how many of our paid impressions have 50% of their pixels on-screen for a full second.

Sort of. And herein lies another topic within the subject of viewability: the methodology and accuracy of the technology being used to measure it.  There are differing confidence levels about the accuracy of what is being reported by the tools currently available, and notable inconsistencies between measurement vendors. Outside of variances in the reporting, significant challenges exist for custom ad placements, namely high impact units like page takeovers. But wherever possible, advertisers are keeping a watchful eye on the viewability of our campaigns, and the technologies will only improve. So what should we expect and what should we pay for?

One obvious way to circumvent low-viewability issues is for advertisers to start paying for viewable impressions only. Advertisers and vendors agree on a CPVM (cost-per-viewable-impression) rather than a CPM, and non-viewable impressions no longer matter. The IAB offers an alternative solution in their 2015 Transaction Principles, which recommend that advertisers and vendors continue to use the CPM metric for billing purposes, but vendors guarantee a viewability threshold of 70% and any shortfall be made good (much like TV stations run under-delivery for ratings deficiencies).  The CPVM pricing structure and the CPM with guaranteed viewability percentages are two potential solutions right now, and at least one publisher, Financial Times, is testing a third. They recently introduced the “cost-per-hour,” a time-based currency. This structure ensures that an ad is 100% viewable for five seconds or more. The currency is driven by the idea that the more time a user is exposed to a brand, the more valuable the impression. It’s an interesting concept, but whether it becomes more widely utilized, only ‘time’ will tell.