Viewability
01 Definition
Viewability meaning: A measure of whether an ad actually appeared on screen where a person could see it.
Viewability tracks the share of ad impressions that had a real chance to be seen. The common MRC standard counts a display ad as viewable when at least 50% of its pixels show for one second, or two seconds for video. It measures opportunity to see, not actual attention.
Why it matters
How Viewability fits the work
Viewability separates impressions that could be seen from those served below the fold or off screen, which improves how you judge ad spend quality.
In context
Of 100,000 display impressions, 68,000 met the 50% pixels for one second standard, giving a viewability rate of 68%.
Practical note
Viewable does not mean noticed. Some impressions cannot be measured at all, so reported viewability covers only measurable inventory, not every ad served.