Optimization glossary

Viewable impression

What is a viewable impression?

A viewable impression is a standard measure of ad viewability defined by the International Advertising Bureau (IAB) to be an ad, which appears at least 50% on screen for more than one second. Viewable impressions are the metric that advertisers use to quantify the percentage of ads that are actually viewed by real people.

Why viewable impressions are important

While online advertising has been slow to adopt technology that ensures that an impression is actually an impression – that a real live human user has viewed the creative – this is finally beginning to change.

The problem with counting impressions without taking viewability into account is that the advertiser is often paying for inventory, which isn’t actually being seen by people. Viewable impressions provide a superior metric that better captures how many ads are being seen.

Knowing that the ad is being seen allows advertisers to more precisely measure ad performance. The shift from impressions served to impressions viewed means that ad placement and ad performance are important metrics for publishers to keep track of in order to maximize their ad revenue.

Reasons for impressions to not be considered viewable

There are a number of potential reasons why an ad impression may be served, but the ad may not be viewable.

  • The user leaves the page before one second is up
  • The user doesn’t scroll down far enough to see the ad
  • The user has ad-blocking software enabled
  • The page is being opened by a proxy server, crawler or spider (not a real person)
  • The user’s computer is missing a necessary plug-in to display interactive media
  • The user tries to open the page on a device that isn’t enabled

How to increase viewable impressions

Publishers can increase the number of viewable impressions on their pages by designing their pages to be optimized for viewability.

For example, they can design their pages with all ad units above the fold, or shorten the length of their pages.

Alternately, they can offer a ‘sticky’ ad unit that remains locked in a specific location even when the user scrolls down on the page.

Publishers can also make their sites mobile-friendly by using responsive templates that resize ads according to the device where it is being viewed. Avoiding technologies such as Flash, which are not compatible with many mobile devices, can also increase viewable impressions.

Finally, improving the load time of the site and of the ads can also improve ad viewability, since ads that take too long to load are often not seen.

Using A/B testing to improve viewable impressions

It is becoming increasingly common to align website optimization testing with the measurement of viewability and attention metrics.

A/B testing with a platform like Optimizely can help publishers improve their viewable impressions because Optimizely integrates seamlessly with Moat, one of the leading analytics platforms for viewability.

Publishers using Optimizely for their A/B testing can set up a series of tests to assess page layouts to ensure the highest levels of viewability, performance and ROI for their ad placements.