Viewability Explained: How to Approach the Concept of Viewable Ads

Illustrative graphic of an eye looking at an ad

Viewability is a buzzword that surfaces continuously in the ad tech industry, and with so many different players in the space, it can be a convoluted topic to discuss. Even the IAB’s viewability definition leaves marketers in disagreement, with more than 4 in 10 respondents admitting the industry could do better in explaining what it is. There is definitely still room for improvement.

If you are not familiar with IAB’s definition of viewability, we have broken it down. An ad is viewable if:

  • At least 50% of the display ad is in view for 1 second.
  • At least 50% of the video ad is in view for 2 consecutive seconds.

For video, it’s important to differentiate between viewability and video viewing. Viewability by this definition means the video ad is shown, however does not necessarily mean the video was watched from beginning to end. A video might be viewable by the IAB’s standards, but the user does not actually watch the entire ad, if at all.

In conjunction with the IAB, The Media Ratings Council (MRC) has compiled a list of viewable impression ad measurement guidelines to help advertisers decipher viewability for themselves.

What is Viewable Inventory

Taking the time to read the guidelines for viewability measurement and examine how it is translated into your digital campaigns can benefit you when pitching a campaign, or explaining results to your client.

Unfortunately, grasping the concept of viewable ads, figuring out how to capture viewable impressions, and measure the results is becoming an increasingly daunting task for advertisers, as more players enter the space. Don’t worry, the onus is not only on you!

DSPs, Exchanges and 3rd-party data providers are also accountable to provide information where possible. The task you need to focus on is finding out how each partner defines viewable inventory, and how much of it is available to you.

For example, one partner might identify 60% of all inventory as viewable impressions. If this is the case, then 40% of inventory is either unmeasurable or unclassified. Understanding how your advertising partner defines viewability and measures it will ensure you are capturing the impressions that you are looking for.

What is a Viewable Impression

Just because a partner says an impression is viewable, does not mean that all other impressions are never going to be seen by a viewer. As mentioned, some impressions are simply unmeasurable or unclassified. That said, if you only want to bid on the 60% that is explicitly deemed viewable, you can set up your campaign to bid only on these impressions. As always, this comes with some constraints, including higher costs, lessened reach and limited scale.

In many cases, you will need to employ a 3rd-party segment or tracking tool to bid on impressions that are identified as viewable. This increases the probability that your ads are being viewed by the user, but also comes with an added fee. The additional cost to your campaigns is often comparable to the amount required to bid on Private Marketplace deals.

It’s a delicate balancing act between achieving a reasonable viewability percentage, maintaining your reach, and staying in budget.

Finding the Right Balance

Now you’re equipped with the knowledge of what viewability is and how focusing on viewable impressions can affect your campaigns. Here’s the fun part! You can make strategic decisions to overcome the difficulty with viewability in programmatic. Here are some examples:

1. Consider Your Native, Display, and Video, Ad Placements

If you can carefully select your ad placements, you can increase your chances of bidding on viewable impressions, without the extra cost.

  • Native Ads: Although native ads face similar challenges to display ads when it comes to viewability on desktop and mobile web, in-app native ads are often viewable, as the impressions should only load when in-view. Although this is immensely appealing, this format has tracking limitations. Since the ad containers in which in-app ads are rendered are unique to each app, external measurement is difficult.
  • Display Ads: Include 300×600, 160×600 display ad sizes in your campaigns. The length of the creative sizes with 600 position them as a strong contender to stay in-view, as a user scrolls through the content they are reading. Ads that are 728×90 also work well on desktop because they are often displayed at the top of the page, making it load as soon as the user arrives to the desktop site.
  • Video Ads: Try native outstream because the placement loads and plays only when in-view, and eliminates the need to use a 3rd-party verifier, and usually results in a higher rate of video completion. That said, bidding only on inventory classified as in-view, does not always mean you will reach the video completion levels you seek, due to the limited amount of inventory.

2. Buy Impression Based on Bid Performance

Buying impressions on performance-based models, such as CPC/CPCV will help to mitigate the fear of purchasing non-viewable impressions. After all, a user must see an ad in order to click it, so it’s the best of two worlds: you can have scale and guaranteed results.

3. Leverage Private Deals

This is a great way to increase your propensity to buy viewable inventory, as publishers will specifically package viewable ad placements. Keep in mind, these will come at much higher CPMs.

If viewability remains a concern, you can always check with your DSP to see what measures are in place to track viewability. Some platforms will have partnerships or will allow you to integrate trackers to evaluate the campaigns you set up. It’s important to keep in mind that measuring viewability is not possible for all inventory sources, and it’s a work in progress for the industry as a whole.

How StackAdapt Can Help

Our latest feature leverages machine learning to enable you to set a Viewability Goal for your display and video campaigns.

StackAdapt also helps advertisers leverage deals through StackAdapt Deals—our packaged, customizable deals, which include those focused on high viewability across native, display, and video.

Want to reach your viewability goals? Request a demo to learn more about StackAdapt.

Eli Bardikoff
Eli Bardikoff

VP of Sales


A veteran member of the Sales team, Eli oversees one of the core sales teams who focuses on helping existing clients and new prospects get the most out of their investment from StackAdapt—not to mention run high-performing campaigns.