What is viewability?

Viewability is a measure of how often an impression is actually seen by a user. For example, an ad that is served at the bottom of a page that requires a user to scroll to see it will likely have a lower viewability score than an ad that loads at the top of a page. The IAB defines an ad as viewable in the following ways:

For ads, 50% of the ad's pixels are visible in the browser window for a continuous one second.
For larger ads (those greater than 242,000 pixels), 30% of the ad's pixels are visible in the browser window.
For in-stream video ads, 50% of the ad's pixels must be visible in the browser window for a continuous two seconds.

How is it measured?

In order to calculate a viewability score, Index Exchange (Index) works with Integral Ad Science (IAS) to measure a sample of impressions that have transacted on our exchange. When an ad is rendered on a user's page, a pixel fires and it captures events that determine whether the ad was viewable in the user's web browser, mobile web, or mobile app.

After we've measured impressions and logged the results, we use the data to calculate the average viewability for traffic based on a unique combination of the following three dimensions:

Site ID
Top-level domain (for web) OR app bundle (mobile app)
Ad size (only used for display traffic)

We require at least 10 samples in order to calculate a score and use a lookback window to make sure that we are not including stale data.

How is a viewability value provided in a bid request?

DSPs receive viewability data in the imp.metric object of an OpenRTB bid request. In the following example, Index has measured the estimated viewability of this bid request to be viewable to a user at least 70% of the time.

{
	"id": "1928474302",
	"imp": [
		{
			"id": "1",
			"banner": { "w": 300, "h":250, "pos": 0},
			"metric": [
				{
					"type": "viewability",
					"value": 0.70,
					"vendor": "INDEXEXCHANGE"
				}
			],
		}
	]
}

What can you do with a viewability score?

Media Owners and Buyers

Media Owners and buyers can set up deals that target a minimum viewability score. This means that if a viewability score in an incoming bid request that is eligible to be a deal does not meet the minimum viewability targeting value set in the deal, then a deal will not be activated for this bid request. For more information, see Viewability targeting in deals.

Media Owners can also create reports that include viewability data to help them manage their viewability targeted deals and generally understand the viewability of their inventory on our exchange. For more information, see Create a custom report.

DSPs