Viewability Management

“Just because an ad is served, does not mean the impression could actually be seen” – Google


Decisive assessment of advertising performance in digital media has long been a challenge; Google reported in December 2014 that 56 percent of all display ad impressions were never in view of the users.

Impression Viewability

Viewability indicates whether or not an impression had a chance to be seen; Viewability metrics quantify the value of digital media by differentiating viewable impressions from the impressions served. Consistent and reliable measurement of viewable impressions contributes to greater AdTech ecosystem transparency and helps build trust across the supply chain.

Viewability Standards

Collective industry standards, developed by the Interactive Advertising Bureau (IAB) in collaboration with the Media Rating Council (MRC), define display ad Viewability Threshold as 50% of the ad in-view for at least one second (30% for large display ads of 242,500 pixels or more, and two seconds for video ads).

BidCore Viewability Measurement

Measuring Viewability verifies ad exposure and provides feedback on the quality of impressions for assessing supply inventory, optimizing selection, and maximizing the return on Ad Spend. Viewability metrics provide input for probability modeling, predictive analytics, and outcome-driven optimization strategies in digital ad campaigns.

  • Viewability Measurement is presently available only for display (banner) ads.

Viewability Tags

Viewability is verified using small snippets of JavaScript code — Viewability Tags — imbedded in creatives as they are served to Supply Partners; the code executes in the user’s browser as it loads the page with the ad.

  • Viewability Tags work with all mainstream, JavaScript-enabled browsers; for the very few users who disable or lack JavaScript support, Viewability is not measured.

Viewability Events

Tags capture and report two distinct, successive impression-level events, as they take place in the user’s browser:

  • Measurable Impressions are reported as soon as the browser loads the Tag, verifying that the Creative was displayed.

  • Viewable Impressions are reported only once the industry-standard Viewability Threshold is met, verifying that the impression was in-view and the ad had a chance to be seen.

Viewability Data

Tags report Viewability events through HTTP requests back to BidCore, where raw Viewability data is compressed and transformed into aggregates for reporting and analytics.

Viewability Metrics

  • Measurable Impressions — the number of impressions loaded in user devices

  • Viewable Impressions — the number of impressions that were in-view

  • Viewability Rate — rate of Viewable Impressions to Measurable Impressions

u-Slicer Reporting

Viewability metrics are available in u-Slicer Reporting Tool by selecting Viewability Vendor filter for Traffic.

Measurement Process

  1. Viewability macros are included in the Creative Asset’s HTML code

  2. As the Creative is served, BidCore replaces these macros with relevant Viewability Tags

  3. As the page with Creative is loaded, Tags activate in the user’s browser and report a Measurable Impression

  4. Once the viewability threshold is reached, Tags report a Viewable Impression

Viewability Macros

Viewability macros are inserted in the Creative Asset’s HTML code along with other pixels and tags, as described in the Creative Management; two macros are required, one for each Viewability event:

#Viewability Macro to report Measurable Impressions
#Viewability Macro to report Viewable Impressions
#Sample Creative HTML with Viewability Macros
<a href="${CLICK_URL}${CLICK_THROUGH_URL_ESC}" target="_blank">
<img style="border: 0;" border="0" width="${WIDTH}" height="${HEIGHT}" src=""/>
<script type="text/javascript">
var vmjs = new vmjs.VMJS({
eventTrackers: {