The average viewability of video ads across the Web -- not including YouTube -- is 54%, and on YouTube it is 91%. It's no surprise that video ads are significantly more viewable on mobile and tablet than on the desktop, but it highlights the shocking fact that 46% of video ads across the Web are never seen, and 76% of non-viewable ads never had a chance to be seen because they are hidden by another page or tab.

Out of the billions of digital video ad impressions measured each year, about one in four are presented below the fold, muted or stuffed inside of display banners. This represents millions of dollars of waste across the industry. On the plus side, there are tools available to detect and eliminate much of this waste.