RealVu is NOT after-the-fact verification or historical targeting.
Only buy ad units that are in view. RealVu’s proprietary Content Rendering Control (CRC) technology checks every ad unit for viewability in real time before you bid, delivering the highest view rates in the industry.
Other viewablity pre-bid solutions (such as IAS) use the historic viewability performance of a website to “target” websites that are more “likely” to be viewable. The websites are rated based on their past viewability performance. You still buy impressions and hope yours is viewable.