Viewableimpression

Viewable impression is a digital advertising metric indicating that an impression had a reasonable chance to be seen by a user. It represents a subset of all served impressions, filtered by a standard for what counts as “in view.” The concept is used to assess how much of an ad actually appeared on a user’s screen long enough to be noticed, rather than merely being loaded.

Industry standards for viewability are defined by the IAB Tech Lab in collaboration with the Media Rating Council (MRC) and measurement vendors. For display ads, an impression is considered viewable when at least 50% of the ad’s pixels are in view on the user’s screen for a minimum duration (typically 1 second). For video ads, viewability generally requires at least 50% of the video’s pixels in view and the video to have played for a minimum period (commonly 2 seconds). These thresholds are implemented by third-party measurement services that use signals such as screen visibility and time in view.

In practice, viewable impressions are used to price and optimize campaigns, with metrics such as viewable CPM (vCPM) guiding buying decisions. Advertisers rely on viewability data to compare placements, assess quality, and report performance to stakeholders. However, viewability does not measure engagement or effectiveness beyond visibility, and counts can vary by device, format, and measurement provider due to differences in how viewability is tracked and verified.