MobileFuse counts impressions in three different ways, depending on the media type. MobileFuse does not currently require a creative to be viewable to count an impression (though we do monitor and optimize supply for viewability and brand safety!).

In all cases, MobileFuse will only ever count a single impression per bid request, so duplicate impressions are filtered out.

Display

For display creatives, MobileFuse appends an impression pixel (via an <img> tag) to the HTML ad markup. This causes the impression for display units (including rich media) to count directly after the creative starts to render.

Video

For video (VAST) creatives, MobileFuse includes an impression pixel URL (via an <Impression> element) to the VAST XML ad markup. This causes the impression to track whenever the video player invokes impressions. For most players (including the one bundled in the MobileFuse SDK), this happens as soon as the video starts playing (after the player assets have loaded the video has buffered).

DuoBid

For DuoBid, the experience is unique, because buyers are purchasing VAST, but the unit itself is in the form of a rich media display unit to the publisher. For this reason, MobileFuse tracks the impression when the video has buffered, and the publisher will typically track the impression as if it were a display unit. For this reason, higher than usual discrepancies between MobileFuse and publishers are typical when DuoBid is enabled (since the publisher will track as soon as the creative starts to render, and MF will track after most of the assets will loaded).