Seeing is believing – the current state of mobile viewability

Soma Tóth

Data Scientist

We have written about the importance of viewability in digital advertising early last year. Ever since we have gathered a lot of experience and many things have changed in the industry, so we decided to dedicate a second overview to this topic.

The requirements of mobile viewability

First of all, lets refresh the meaning of mobile viewability. Basically it is a metric that is supposed to confirm that the displayed ad may have been perceivable by a real user. I use conditional tense because viewability only able to tell if the ad was at the right place of the screen for the right period of time, so there was a chance of reception (OTS – opportunity to see). Currently we are not able to tell if the reception has actually taken place (and the user didn’t look away from the screen at the moment).

Therefore, we talk about one viewable impression when the creative was loaded in a zone which was in the focus of the user’s screen for a certain time. The metric is usually given in percentage form and demonstrates the ratio of viewable impressions compared to all impressions (for example if 7 impressions were viewable from total 10, then it means 70% viewability rate).

In the summer of 2016 the first official, professional specification of mobile viewability was finally defined. Thus the MRC (Media Rating Council) guideline was made for the players of the American market on the first place and based on US market data, it is incredibly useful as the first professional guidance dedicated to mobile viewability.

The MRC guideline – in accordance with the practice followed so far – defines two main criteria to declare a mobile ad as viewable:

  • at least 50% of the ad’s pixels
  • at least for 1 (in case of video creatives 2) continuous second

are displayed in the viewable part of the user’s screen (in the active browser window or in the active application). The pixel requirement always has to be fulfilled before the time criterion is fulfilled (in other words the clock only starts when the pixel visibility has reached 50%).

The requirements of mobile viewability technically are the same as the cornerstone numbers used to define desktop viewability (50% and 1 second in both cases). Some experts have expressed their displeasure about that sameness. They argue while on desktop more ads may be displayed on one screen at the same time (and all of them will be considered viewable after 1 second), but due to the size of the screens on mobile only one, maximum two ads fit in at the same time. So either the definition of desktop viewability is to broad or the mobile’s is too strict compared to desktop, but the current status quo is definitely not consequent.

The most important (and positive) difference between the two platforms is that viewability measurement on mobile could only start after the ad is completely loaded. On desktop this requirement is not specified separately.

Obviously several further limitations should be used during applying mobile viewability correctly, but we will not discuss these in detail now.

The technological diversity and difficulties of measuring mobile viewability   

We work with Moat, one of the biggest international analyst company that operates in this business, and is one of the two companies doing mobile viewability accredited by MRC.

The definition underlines that ads appear in two environments:

  • in mobile web (browser), or
  • in applications

In case of mobile applications an SDK (Software Development Kit) must be built in the app to measure viewability. (By the way the MRAID (Mobile Rich Media Ad Interface Definition) protocol, developed by IAB is also usable for this purpose (as well), but this process is not accredited by MRC in its present form.) This method is a bit more complicated and time-consuming than putting a code-fragment into a website. Thus, despite the agency/advertiser would like to measure viewability of an ad running in apps, it’s not possible if there is no such dedicated software element in it and have to wait until a version is released in which the developers have built that component.

Due to the apps’ structural characteristics (predominantly all content is on one screen, so scrolling is not necessary) the 50%-pixel requirement mostly always fulfils, only the time factor is questionable. All in all, according to our measurements, viewability rate in apps is over 90%.

In mobile browsers measuring viewability is mostly conducted with javascript codes. Within mobile web impressions we can distinguish two different types: feed and non-feed sites. For instance, belongs into the first type: the content is endless and loaded automatically by scrolling. Some data shows that in feed environment less than 1 second is enough for the users to perceive the ad. MRC has not made a difference in this regard when defined viewability, although has created a separate category of the „sub-second ad impression”. It describes viewable impressions longer than 0,5 but shorter than 1 second. By definition these are not considered as full right viewable impressions, but the viewability companies are encouraged to mark these impressions separately, so the agencies/advertisers could decide on their own whether to count these feed impressions viewable or not.

Impressions purchased in programmatic systems rise further difficulties regarding viewability. In case of open RTB purchases millions of sites are available around the globe. Therefore, the advertiser is not able to check one by one if the settings of the ad zone/viewability code are correct and standardized. Thus, measuring viewability might differ significantly on each site. One of its reasons on the technical side for instance are inadequate usage of the popular HTML elements, the iframes. If the measuring code is invited into an iframe that has a different source than the website (content) itself, then because of the security settings the Moat code couldn’t measure outside the iframe.

Viewability has outstanding significance primarily in branding campaigns, where the purchase is based on impressions (CPM). In performance campaigns (where the base of purchase is conversion) this number is less important for the advertiser, because the payment doesn’t depends on it.

It’s clear that the birth of the first official viewability standard is a lot welcomed, but the technical background of the mobile platform is in need for standardizing and unifying (with collectively accepted protocols and standards) to gather correct and real viewability rates.

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