Report on performance

How Active View measures viewability

MRC Viewable Ad Impression guidelines specify that viewability vendors should measure the ad itself instead of its containing iframe. Active View uses the following techniques to implement this policy:

  1. During rendering: A <div> with id=GoogleActiveViewElement is injected around the creative element to identify its precise location within the ad response.
  2. During viewability measurement: Active View will locate this <div> and measure the exposure of the wrapped creative element instead of the containing ad iframe.

Active View will start measurement as soon as it determines that the wrapped creative element has loaded. In most cases, Active View will use the Intersection Observer API to measure viewability, while relying on other techniques on older browsers.

Sometimes, the creative <div> collapses to zero size and cannot be used directly for measurement. There are two main causes:

  • Use of style attributes that prevent the <div> from capturing the correct geometry (for example, position=absolute).
    • Active View will search for an image, frame, or iframe element within the <div> that is larger than the minimum size of 30 pixels. If found, Active View will measure the exposure of that element directly.
    • If multiple candidates exist within the same creative <div>, Active View will measure the largest element.
  • Custom JavaScript executed as the creative payload that inserts the actual content somewhere else within the ad iframe, but outside of the creative <div>.
    • Active View will search for a second <div> with the class attribute GoogleActiveViewInnerContainer. This <div> expands to the size of the ad container, but allows the container size to be measured from within the ad iframe.


Why would an ad slot have unexpectedly low visibility and be classified as "unviewed"?

The most common cause is header bidding, in which the ad creative is either never inserted into the page or is inserted somewhere outside the creative <div>.

Are custom creatives or out-of-page creatives measurable?

Any creative-rendering behavior that prevents the size of the creative content from being captured by a <div> is not supported and cannot be guaranteed to work with Active View measurement.

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