Impression

An impression is the fundamental unit of measurement in digital advertising, representing a single instance of an advertisement being displayed to an audience. In online advertising, one impression equals one ad being loaded in a browser or app. In out-of-home and retail media advertising, the definition is more nuanced — an impression typically represents one person having the opportunity to see an advertisement on a screen.

For digital out-of-home and retail media, impressions are calculated using audience measurement data rather than device-level tracking. A screen displaying an advertisement to 50 people simultaneously generates 50 impressions. Impression counts are derived from footfall data, attention analytics, or Bluetooth sensor data that estimates the number of people in front of a screen during a given play.

Impressions are the basis for CPM (cost per thousand impressions) pricing in programmatic advertising. The quality of impression data significantly affects the value of retail media inventory — verified impressions backed by audience measurement data command higher CPMs than estimated impressions based on general footfall averages. The Adflux Attention Analytics module provides verified impression counts for every screen in a network, enabling retailers to sell premium, audience-verified inventory to programmatic buyers.