Mobile is another story, though. And that’s where the MRC’s latest guidance report on mobile viewable impressions comes in. And so far there’s no way to officially, from MRC’s perspective, count viewable served ads in an app context. A crucial hangup is Flash, which iOS doesn’t support. Flash is used to help detect whether an ad is viewable. Another process, called geometric triangulation, can be used as a substitute, but that doesn’t work for cross-domain iframes for ads served by a third party. The served ad impression standards released last June apply to a desktop environment. Mobile complicates things because users can browse and see ads in the mobile web or view ads in an app environment. The full guidelines are available here. Until the MRC and other organizations such as the IAB, 4As and the ANA devise a standard measurement for a viewable ad on mobile, the MRC’s interim guidance report was released as a half-step measure. Unlike TV and radio—when you see or hear an ad, you know it’s been served—digital ads have been counted even when they’re not visible on the page. Over the last few years, the MRC developed minimum standards that needed to be met before a digital ad, on a page or in in a video, could be officially counted. Those standards were released last June. A new metric, called the Loaded Ad, can be counted in an app, but does not qualify as a viewable impression, according to the MRC. “We’re allowing that to be used while we develop the technology to measure ads,” says Ivie. “The loaded ad is a temporary term, just applicable to apps.” So far a little more than a dozen measurement vendors have been audited and accredited by the MRC to count those impressions. The Media Rating Council, an association that vets and accredits third-party measurement services across television, radio, print and digital platforms in order to ensure standard practices, has been working on an ambitious project. The group wants to develop a standard system of audience metrics across all of the media it represents. But there’s been a significant hurdle to that end goal: the served ad impression. For digital display ads, 50 percent of the pixels needed to be in the viewable portion of the browser window for at least one second. In video, it’s a least two seconds. “The way you measure viewability in those two environments is different,” says George Ivie, CEO and executive director of the MRC.