An “Impression” (JS Tag only) is counted based on different criteria, depending on the format:
Banner/Rich Media (Display Ad Impressions)
An impression is counted at a minimum on begin-to-render. Within all modern browsers supporting the
An impression is counted after the ad has completed buffering and the video has started playing.
A “Tracked Ad” is counted when the impression is rendered, the JS Tag is incompletely executed, the ad unit was not found, or when clients are using the pixel instead of JS Tag. This should be the metric client should use to count the total number of requests.