Impression (Internet)


An impression (or view) is “a single display of online content to a user’s web-enabled device.” It’s the number of times the ad is displayed, whether it is clicked on or not. Each display counts as a single impression.

“Many websites sell advertising space by the number of impressions displayed to users. An online advertisement impression is a single appearance of an advertisement on a web page. Each time an advertisement loads onto a user’s screen, the ad server may count that loading as one impression. However, the ad server may be programmed to exclude from the count certain non-qualifying activity such as a reload, internal user actions, and other events that the advertiser and ad serving company agreed to not count.”[1]

Because of the possibility of click fraud, robotic activity is usually filtered and excluded. Thus, a more technical definition is given for accounting purposes by the IAB, a standards and watchdog industry group: Impression is “a measurement of responses from a web server to a page request from the user browser, which is filtered from robotic activity and error codes, and is recorded at a point as close as possible to opportunity to see the page by the user.”[2]


Counting impressions is a method of estimating “opportunities to see” and the cost is quoted in cost per impression (CPI). (By contrast, cost per click is not impression-based).


The process of estimating reach and frequency begins with data that sum all of the impressions from different advertisements to arrive at total “gross” impressions.
Impressions (#) = Reach (#) x Average Frequency (#)

Served Impressions versus Viewable Impressions

A movement is underway to move from the current standard of served impressions, to a new standard of viewable impressions. The Interactive Advertising Bureau (IAB), Association of National Advertisers (ANA), and the American Association of Advertising Agencies (4A’s) have joined forces in an initiative called 3MS (Making Measurement Make Sense), with the purpose of better defining the value of display media.[3]

Served impressions are the current industry standard and “measure whether an ad had been served by an ad server, not if it is rendered on the screen fully enough and for a long enough time for consumers to see it.”[4]

The 3MS advocates a switch to viewable impressions. On March 31, 2014, The Media Rating Council lifted its advisory on viewable impressions and gave a “green light to the industry to begin transacting on the new metric for the first time.”[5]


  1. ^ IAB. IAB Interactive Advertising Wiki: Impression
  2. ^ IAB. Glossary of Interactive Advertising Terms v. 2.0. 
  3. ^ Mane, Sherill. Measuring Return From Interactive Advertising. MASB Summer Board Meeting and Summit, August 2012.
  4. ^ 3MS. Principles and Solutions: Defining Impressions.
  5. ^ 3MS. Press Release: Media Rating Council Lifts Advisory on Viewable Impressions for Display Ads.

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