Viewability metrics
Viewability metrics are frequently found on the best DSP's, where by default, the DSP is measuring the viewability of all impressions bought. If the DSP does not measure the viewability, you will be able to integrate a third party provider to measure the viewability, like IAS or Meetrics.
According to Appnexus, "Viewability measurement is achieved using javascript embedded within each creative, which is then called for each individual ad impression. The script launches automatically as the page loads and immediately starts measuring if and when the creative is viewable based on a variety of measures. These may include whether a web or browser tab is in focus, whether a particular ad is in view of a user based on where on the page the user has scrolled to, how long an ad was visible based on these metrics, and other factors." Now more here about the viewability standards.
Here the frequent metrics:
Measurable Impressions
The number of impressions that were measurable for viewability. An ad is measurable when the tag is able to capture viewability data about the impression.
Viewable Impressions
The number of impressions on the site that were viewable out of all measurable impressions.
Here the less frequent available metrics:
Eligible Impressions
The number of impressions that were eligible to measure viewability. An impression is eligible if the ad unit has a supported creative format and tag type.
Impressions Visible 10 Seconds
Video impressions visible for 10 seconds.
Average Viewable Time
The average time, in seconds, the ad appeared on screen. Some DSP's can have a cap on the measurable lenght.
Impressions Audible and Visible at Start
Number of impressions audible (audio was at 10% or higher) and viewable on start of the video.
Impressions Audible and Visible at First Quartile
Number of impressions audible (audio was at 10% or higher) on 25% of the video.
Impressions Audible and Visible at Midpoint
Number of impressions audible (audio was at 10% or higher) on 50% of the video.
Impressions Audible and Visible at Third Quartile
Number of impressions audible (audio was at 10% or higher) on 75% of the video.
Impressions Audible and Visible at Completion
Number of impressions audible (audio was at 10% or higher) on 100% of the video.
Impressions Audible and Visible at Completion
Number of impressions audible (audio was at 10% or higher) on 100% of the video.
Full-Screen
Number of impressions that were put in full-screen mode at any time during play.
Play Time Audible
Average time, in seconds, the ad appeared in screen and was audible (audio was at 10% or higher).