While this problem persists advertisers will be paying to serve ads that will never be viewable to users.

To shed some light on this issue, Kellogg’s and BrightRoll ran a study that evaluated how different companies tracked the viewability of different ad units.

For more on this topic, read our guide to viewability in online advertising and this post on why measures of digital marketing ROI are meaningless unless ads are viewable.

The methodology

Each viewability measurement company (VMC) was asked to provide the following measurement for every video impression:

The VMCs involved in the study were narrowed down to those that offer solutions based on the IAB VPAID standard, are compatible with programmatic buying, and were independent measurement company with no media buying capabilities.

Kellogg’s then ran 40 different tests that varied based on different scrolling behaviours, browser type and the presence of iframes.

This table shows the accuracy with which each of the VMCs was able to measure the viewability of the different ad scenarios.

Some clearly performed better than others, but none of them achieved 100% accuracy across the board.

The results show that the consistency associated with display viewability measurement does not hold true in video viewability measurement.

The accuracy of various measurement partners varied primarily based on user behaviour (whether the user scrolled during playback) and based on browser/iframe combinations.