San Mateo, Calif.—Advertising technology company Adap.tv Inc. has introduced a service that verifies the viewability of video ads in real time and blocks impressions that do not appear to the viewer.

The company's Certified Viewability tool monitors where video ads appear, authenticating the size of the video player and its position within the browser window. It then enables advertisers to specify whether they want to target viewable-only impressions (for example, those video ads that appear only “above the fold”) before the first ad request is sent, the company said in a statement.

Adap.tv said Certified Viewability is an industry first. It is being offered free to agencies, publishers and ad networks.