Glossary keyword - Impression





Served vs. Viewable Impression



The term impression, which is used in the context of online advertising, refers to when an ad is taken from its source and can be counted. But when the ad is clicked on, this is not taken into account. This means that when an ad is fetched, this is considered to be one impression. 

To lower the chances of click fraud, activities that seem robotic are excluded and filtered out. For accounting purposes, a more technical definition is given by the IAB, which is a watchdog and standards group. According to them, an Impression is a measurement of responses coming from a web server to a page request. This comes from the user browser and is filtered from any error codes and robotic activities. All of these actions are recorded at a point which is close as it can be to be seen by the user of the page. 

Purpose of Impression

The purpose of Impression is to pay and account for most of the Web advertising. The cost of the service is quoted in CPIs (cost per Impression) or CPMs (cost per thousand impressions). Contrast CPC, on the other hand, is the cost per click and is not Impression based.


A new move is pushing developers to abandon the current standard of served impressions. The new standard is being called viewable impressions. The Association of National Advertisers, American Association of Advertising Agencies (the 4 A’s), and the Interactive Advertising Bureau (IAB) are joining together to better define display media’s value. 

  • Served Impressions are the standards of today. This standard is recorded by ad servers to see if the advertisement is fully loaded and visible to the viewer. 

  • Viewable impressions, on the other hand, are seen as ads that are at least 50 percent visible to the viewer for at least one second. 

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