Ad Server Verification – Understanding Viewable Impressions

the Gaze

the Gaze

Viewable impressions

The most commonly discussed verification metric among Agencies and Advertisers is Viewability. Viewability describes how much of the ad is in view for the end user and viewability is measured on viewable impressions. Viewable impressions at a minimum are impressions served above “the fold” of page as it is viewed in the users the browser. The design of most web pages contains content which fills the active browser window and trails off below the bottom fold: hidden from view. Scrolling down the browser using the scroll bar, reveals the hidden content and content disappears at the top of the browser. Strictly speaking each of the sides of the browser window are ‘folds’ as the content can disappear behind any of them if the page is designed to scroll in those directions.


The viewable impression count is triggered by a JavaScript embedded in the ad code which checks how much of the ad is in view and for how long (the same technology can be used to reveal if the ad is served into the active window or tab). Some Publishers offer their inventory classified by whether the placement appears above or below the fold, and price the inventory accordingly. Increasingly in the digital marketing space, viewable impression complexity is causing advancement the capabilities of the verification measurement technologies.


As the IAB develop a fixed standard for viewable impressions; Advertisers are seeking the ability to have a flexible definition of “viewable impressions”. These definitions consist of a percentage of the surface of the ad exposed to the user, for a set duration of time. User impressions that match a definition such as 90% of an ad seen for 5 seconds and above, fall into this categorization of viewable impressions. This is called a “viewability threshold”.

Ad server reporting reveals the total number of viewable impressions against each placement and when combined with media cost data, can show the Advertiser how much media spend they are wasting on ads not in view. Some Publishers will have contractual agreements with major Advertisers and big Agencies where the media cost for a viewable impression inventory reflects a standardised definition between the two parties or the definition set by the IAB. The third party ad server enables a customised threshold to be set by the trafficker at the Advertiser or Campaign levels and the data is collected and presented based on the definition.


Viewable impressions are under high demand from an industry that believes that this new metric will challenge the usual definition of standard impressions in the future. Some believe that since ads that are not being seen (according to the viewable definition) they should be dis-associated from post impression conversions and subsequent attribution. This presents interesting questions for rich media content where audio is automatically enabled; ads that are heard and not seen are still a grey area for digital measurement. In addition to the ad servers providing a record of viewable impressions, point solutions are also available for measuring viewable impressions such as Alenty; who bring to the table a more “dynamic threshold” methodology (where the threshold does not need to be set before the campaign begins, but the trafficker can choose the definition when the report is pulled).


Viewability is harder to measure than content categorization because it requires JavaScript which means it is more complex to execute on Instream and Mobile ads. Viewability is also much harder for the Publisher to control and many Publishers are well aware that a fair amount of their inventory may never be seen but won’t be aware of it until the ad is served. Such Publishers might argue that their pricing for the inventory is adjusted to reflect the possibility of wastage from viewability which is a conundrum for the Advertiser unless viewability can be guaranteed in the IO. To assist in eradicating this wastage some technologies are being developed that only make a request to the ad server once the placement is coming into view, rather than loading the ad tag when the whole page loads.

To find out more about viewability and verification get a copy of: Ad Serving Technology – Understand the Marketing revelation that commercialized the Internet – available now from..

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