NEW YORK: The viewability debate remains unresolved, but in the meantime a number of fixes are becoming available to those advertisers who want to move away from simply paying for ads served, whether visible or not.

AppNexus, the ad tech giant in which holding company WPP made a strategic investment last year, is letting advertisers set their own criteria for what they consider viewable and then pay only for those ads meeting the required standards.

The flip side of that development is that those viewable impressions are likely to cost more, Advertising Age reported.

"You can buy viewable impressions for the same as non-viewable today," said CEO Brian O'Kelley, adding: "I think at some point, when more [advertisers] transact on a viewable currency, you'll see more price competition for viewed impressions."

He acknowledged that not every buyer might want to do that. "According to a [certain] standard, they're not viewed, but there might be some ads that do influence people that don't meet that standard," O'Kelley said.

"If you want to go around buying 40% of an ad seen for one second and make a margin, you can."

Measurement firm Integral Ad Science, meanwhile, has launched a tool that it says will streamline the ability of advertisers and publishers to transact on viewable, non-fraudulent impressions by eliminating discrepancies of up to 20% between buy-side and sell-side measurement: "Pub Expert unifies both sides of a campaign into a single metric of record."

Computer technology business Lenovo has tested the tool and Gary Milner, director of global digital marketing, welcomed the transparency it brought to proceedings, so "strengthening our relationship [with publisher partners] and operational efficiency".

The participation of publishers is of course essential to the success of such ventures. "A publisher does have to agree," said O'Kelley. "So far, we've not had any publisher opt out."

He added that the roster of publishers available through AppNexus – which includes Microsoft, Hearst, Shazam and a local media consortium with members like Cox, Chicago Sun Times and The Boston Globe – acted as a differentiator for the platform.

Another recent development has been the Media Ratings Council's approval of Moat Inc, a third party measurement firm, to track mobile ad viewability, a step which may encourage more spending in this channel.

Data sourced from Advertising Age, Advertising Week, Wall Street Journal; additional content by Warc staff