What is In-View ? and What is viewable impression ?

Display viewable impression

• At least 50% or more of the pixels were in an in-focus tab on the viewable space on the browser page for at least one continuous second, post ad renders
• For large sized display ads: 30% or more of the pixels
• For expandable rich media: it can be based on pixel count of smaller initial tag format or larger, expandable format (needs to be disclosed to the user)

Preroll Video viewable impression
A video ad is deemed viewable if 50% of the ad is visible on a user’s screen for at least two consecutive seconds

MRC accredited viewable impression vendors:
http://www.mediaratingcouncil.org/Digital%20Landscape.pdf

Viewable Display:
AdYapper, Alenty, Chartbeat, comScore vCE Validation, GLAM Media, Google Active View, DoubleVerify (ViewAssure), Integral Ad Science, Moat, RealVu, Sizmek, Spider. I, WebSpectator for Publishers, Yahoo! APT 

Viewable Video:
Moat, Telemetry, Videology 

Components of In View:

The measurement of a viewable impressions considers:

• Quality of affiliate
• Quality of URL
• Tile (placement of ad on page)
• User behavior

MRC Viewable Ad Impression Measurement Guidelines
To provide guidance for the measurement of viewable impressions that supplements existing IAB Measurement Guidelines for display advertising and digital video advertising.

Also By MRC guideline below are the detailed regarding viewable impressions and when not.
http://www.mediaratingcouncil.org/063014%20Viewable%20Ad%20Impression%20Guideline_Final.pdf

• Ad Centric: Relies on counts generated from an ad server’s systems. !!!
• Site Centric: Relies on counts generated from a web property’s systems.
• User Centric: Relies on counts derived in some fashion based on the activity of internet users.
• http://www.mediaratingcouncil.org/Digital%20Landscape.pdf

Source :IAB,MRC