What is an Ad Impression?

An ad impression, also sometimes called a view or ad view, is widely known as the point when an ad is viewed once by a visitor.  However, the actual definition of an impression is when the ad server is called regardless of whether a visitor has seen the ad or not.  An impression is the most common measurement unit in the digital advertising space and one of the most common ways that digital advertising is bought and sold.

Ad impressions shouldn’t be confused with page impressions.  A page impression when the webpage itself loads.  A webpage could have multiple ads displayed so if a visitor views a webpage with five ads, it would be 1 page impression and 5 ad impressions.

Impressions are typically measured by CPM (cost per mille).  If an ad has a CPM of $10, the owner receives $10 every time the ad is displayed 1000 times.  However, advertisers will pay more for ads that gain clicks and conversions since those actions are more valuable.