Why Viewability Matters


What is Viewability?

Viewability is the measurement used to determine whether an ad was viewable to the digital consumer. Viewability tools will enable you to maximise the impact of your digital marketing investment by focusing on impressions that will provide the consumer an opportunity to see the ad.

A viewable ad constitutes a measurement of an ad in-view. That is once the ad hits the area on a web page within the user’s in-focus range, in the visible area of the browser window, for one or two consecutive seconds. Then, and only then, does the consumer have the opportunity to see the ad displayed.

There are industry standard guidelines for measuring viewability. Widely recognised in the industry to be led by the Media Rating Council (MRC) in conjunction with Internet Advertising Bureau (IAB). These guidelines help with regulation so that media buyers and vendors can sing off the same hymn sheet.

Viewability guidelines pending the medium and ad unit size:

  • Desktop Standard Display Ad unit = 50% of ad unit’s pixels are in-view for one consecutive second constitutes the ad being viewable
  • Desktop Video Pre-roll = 50% of ad unit’s pixels are in-view for two consecutive seconds constitutes the ad being viewable
  • Desktop Larger Display Ad unit = 30% of ad unit’s pixels are in-view for one consecutive second constitutes the ad being viewable

Why Viewability Exists

With the arrival of the World Wide Web in the nineties, websites became easily monetiseable. Regardless of whether the content was good enough to keep the user engaged. Irrespective of whether the consumer had the opportunity to see the ad, subsequently classifying the ad as ‘in-view’ at some stage. And here is where the problem lies. Whether content is good or bad, whether ads are seen or not, the media seller would get paid mainly from impressions served, ads clicked or videos played. Whilst ad servers measured these transactional currencies, the measurement of success against marketer’s key objective – to provide consumers with the opportunity to see their ad – was missing. This provided a gaping hole of opportunity to rogue sellers and traffic fraudsters.

Fast forward to the single digits of the noughties, programmatic advertising materialised. Impressions, clicks, video plays are still monetised. However, now with the backing of a 3rd party tool to verify the ad that you, the buyer, are paying for has actually been seen. Viewability makes digital advertising accountable.

Even with the level of sophistication that exists within next generation Demand-Side Platforms (DSPs), up to 60% of ad impressions served can still go unseen, as outlined e-Marketers Ad Viewability report. This is why it is essential to ensure the ad verification tool or service used to measure viewability is independent to the buying platform and media being bought. This way there is no conflict of interest in determining whether the ads are measured in–view.

Standardised Viewability Measurement

It is important to work with media-buying vendors / Demand-Side Platforms that comply with IAB’s standard for measuring viewability. Not having a consistent measurement across your media buys make management of transactions for the viewability measurement extremely difficult.

In 2015, in the IAB’s State of Viewability Transaction article, they concurred that 100% viewability on traded media was ‘unreasonable’. This came down to the fact that not all media is even measureable. There are some viewability tools that have variance between 30-40% in the measurability of a viewable ad impression. Whilst this does not mean the ad is not viewable, not being able to measure the viewability defeats the purpose of having the verification tool or service to begin with.

The interim solution, until technology permits all viewability vendors 100% measurement, is to use 70% as the viewability threshold for measured impressions. This requires the vendor or viewability service you are using to be able to differentiate between measurable and non-measureable viewable impressions. You can then apply a viewable CPM metric (vCPM) to maximise your validated views.

What is a vCPM?

A viewable CPM (vCPM) = CPM / viewability rate (% in-view).

See below campaign examples on how to maximise validated views on a video campaign:

Viewability Campaign Example-ReportPic


  • Vendor 1 performed the best despite having the highest CPM
    • 85% viewability rate (% in-view)
    • 9% increase in impressions viewed vs. Vendor 2, 20% vs. Vendor 3
    • 8% lower vCPM vs. Vendor 2, 17% lower vs. Vendor 3
  • Vendor 3 performed the worst despite having the lowest CPM

When deciding a vendor to partner with, particularly DSPs that will have viewability tools integrated within their platform, look to the viewability rate. This should be one of your key metrics to base your buying decisions on. As the table above shows, looking purely at how cost effective the CPM is could still leave massive room for wastage. The most cost effective CPM will deliver higher impression volumes, however the highest viewability rate will deliver the most viewed impressions and reduce your vCPM. And that’s the buying metric that counts.

Viewability Vendors

Here are my top five viewability vendors to get you started:


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