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Viewable impression
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<p>In the <a href="/facts/Online_advertising/Ncsv0GRz">online advertising</a> industry, a viewable impression is a measure of whether a given advert was actually seen by a human being, as opposed to being out of view or served as the result of automated activity. The viewable impression guidelines are administered by the <a href="/facts/Media_Rating_Council/V13DfuNx">Media Rating Council</a> and require that a minimum of 50% of the pixels in the advertisement be in an in-focus tab on the viewable space of the browser page for at least one continuous second. </p><p>The measurement of ad visibility was first introduced in 2008 by Alenty, and was the first system to deliver reports based on a viewable impression metric for standard IAB (<a href="/facts/Interactive_Advertising_Bureau/aHMHXotJ">Interactive Advertising Bureau</a>) Display ad units, called RealV were developed by Rich Media Worldwide and accredited by the <a href="/facts/Media_Rating_Council/V13DfuNx">Media Rating Council</a> on March 9, 2010. Other companies to offer viewable impressions include DMA-Institute OnScroll, C3 Metrics, Comscore, and AdYapper, while MSNBC utilizes ServeView, a proprietary system in use since 2010. </p><p>The definition of a viewable impression may depend on the type of ad units and the reporting system. For example, a viewable impression for ads of pre-defined size delivered to pre-defined space on the content page is registered by RealVu when the <a href="/facts/Advertising/Hgz271hW">ad content</a> is loaded, rendered, and at least 60% of the ad <a href="/facts/Surface_area/WNowzFCw">surface area</a> is within the visible area of a viewer's <a href="/facts/Web_browser/2pfyymLs">browser window</a> on an in focus <a href="/facts/Web_page/5JK7xQLe">web page</a> for at least one second. <a href="/facts/Click-through/RV3fQ0UC">Click-through</a> is enabled at the moment of the "viewable impression". </p><p>Viewable impressions were developed as an improvement of the <a href="/facts/Impression_(online_media)/yUphonvo">online impression</a> metrics measured by the first <a href="/facts/Ad_serving/wymWeEu9">ad servers</a> developed in the mid-1990s, which analyze HTTP requests in a server log and cannot provide information on events fired by a viewer’s browser; thus, they cannot measure whether ad content was actually visible to a viewer. </p>