Digital ad buyers and sellers have undergone a sometimes painful but necessary transition toward using viewable impressions as currency.
The shift from a served impression to a viewable impression is yet another step to greater accountability in digital media. Viewability is a big issue in display advertising. Publishers willing to be held to this standard will also need to demonstrate that their viewable inventory has been undervalued because its effectiveness has been systematically understated by the non-viewable ads.

In March of 2015, comScore released a report showing that display ad viewability rates did not budge between 2013 and 2014, remaining at 46 percent thoughout.

Quite simmilar situation is in Europe. The percentage of ads that are technically viewable in Europe — 50 percent viewed for longer than a second — has fallen from 63 percent in the third quarter to 58 percent in the fourth quarter of 2015, according to ad verification company Meetrics. Split out by country, Austria slipped the most, from 70 percent viewable ads to 65 percent in the quarter. In the U.K., the picture is bleaker. In the final quarter of 2015, only 50 percent of its display ads were viewable by the IAB and the Media Rating Council (MRC) standards.

In its “State of Viewability Transaction 2015” statement, the Interactive Advertising Bureau (IAB) says that the achievement of 100 percent viewability is “unreasonable”. Longer-loading HTML5 ads means fewer are being seen as users scroll down before the ad loads. Instead an ad campaign should reach a 70 percent viewability threshold, while the industry transitions to buying and selling ads on a viewable impression basis. 

The industry standard requires that for desktop display ads to be considered viewable, 50 percent of their pixels must be in view for a minimum of one second. For desktop video the standard is 50 percent for 2 seconds. In addition, the standard stipulates that for larger desktop ad units, 30% of pixels in view for 1 second constitutes a Viewable ad. Custom ad units and important elements of sponsorships are not consistently measurable today. The measurement standard and the technology are still evolving.