The document aims to provide guidance amid new privacy regulations and the growth of cross-media measurement.
The ongoing need for transparency has resulted in some renewed efforts to hold digital giants to account.
This is the first significant update to the guidelines since 2012.
Few marketers are completely satisfied with current viewability metrics, but video spend is still set to rise.
In Canada 61% of online ads qualify as seen, compared with the global average of 54%, according to Google research on ad viewability.