What counts as an impression in digital out-of-home advertising?
In digital out-of-home, an impression is the count of how many people are exposed to an advertisement play 1. Online, by contrast, an impression is a count of advertisement plays themselves 1. More broadly in out-of-home, an impression represents a single opportunity for an audience member to see the advertisement 2.
How the count is built
The actual impression count in in-store retail media is the total shoppers exposed to digital creative, calculated as Ad Plays multiplied by the media channel or device's Impression Multiplier 1. The Impression Multiplier ideally takes into account foot traffic, observational studies, shopper behaviour analytics and engagement metrics 1. Industry bodies such as Route apply validated research to produce realistic viewing figures for different locations 2.
Conditions an impression must meet
- Impressions should be counted only where the display is viewable within the Visual Exposure Zone, regardless of whether audio is present 1.
- Human presence in the exposure zone must be established through data or sensors 1.
- Dwell Time in the Display Exposure Zone must be considered, and an ad must run at least once during that dwell time 3.
- Gross Impressions are potential ad exposures over a period where presence exists in the exposure zone while the display is functional 3.
- More than one impression can be counted per individual where evidence shows the person transited in and out of the exposure zone on separate occasions 3.
Thresholds and reporting tiers
MRC guidance references IAB measurement principles requiring minimum exposure thresholds, such as 50% of pixels in view for at least 1 second for display ads, adapted for DOOH contexts 1. Reported metric types include Gross Impressions (Rendered), Viewable Impressions (OTS) and Likelihood-to-See Impressions (LTS) 1. All calculations must rest on validated, privacy-compliant exposure data 1.