AppNexus has launched a viewable ad marketplace, enabling buyers to transact only on viewable impressions.

The marketplace uses technology from Alenty, which AppNexus acquired last year, to determine whether ads meet the IABs viewability standards, For the majority of display ads, that means at least 50 per cent of pixels must be visible for at least one continuous second for an impression to count as viewable.

The marketplace operates in real time and provides automated clearing and reconciliation for advertisers.

“The AppNexus viewable marketplace renders digital advertising more accountable and verifiable than all other forms of advertising,” said CEO Brian O’Kelley. “Buyers can use our platform to transact only on viewable impressions, backed by a powerful technology suite that substantiates viewability and automates clearing and reconciliation. The traditional knock against digital advertising was that you never really knew if a human being saw your ad. Now you know – something you can’t say about broadcast, out-of-home or print advertising.”

Want to learn more about viewability? Read our guide to the topic here.