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Ad Viewability: What It Is and How Publishers Can Improve It

Publishers need to track various metrics and data points to ensure that their ads are performing well. One of these is ad viewability, and it’s arguably one of the more critical factors you need to monitor. Not to be confused with impressions, which measures how often an ad is shown, viewability tracks how much of your ads are seen by your audience.

In this article, we’ll explain:

  • What viewability is and how it’s measured.
  • Why publishers should care about ad viewability.
  • Why ads lose viewability.
  • How to optimize your ads to maximize your score.

What Is Ad Viewability?

Some refer to ad viewability as an “actual number of impressions” or viewable impressions, but that’s just a part of what this metric measures. In short, ad viewability tracks two factors:

  • How much of the ad is visible.
  • How long the visible part of the ad is viewable.

Source: Think With Google

Ad viewability only became an issue in 2013, after a report by comScore revealed that 54% of delivered display ads weren’t seen by an audience. The ensuring debates eventually led to the Media Rating Council (MRC) and the Interactive Advertising Bureau (IAB) developing a standard in 2014. According to that, an ad is only considered “viewed” if:

  • 50% of a display ad is in view for one second.
  • 50% of a video ad is in view and watched for two seconds.

Source: Think With Google

Unfortunately, these standards aren’t widely adopted throughout the industry yet. Some advertisers, exchanges, and networks may have different viewability standards, which means that publishers need to pay close attention to the requirements of each platform they work with.

Why Should Publishers Care?

Why do publishers monetize their content? Why do advertisers pay for ad space? The answer is the same for both: to generate revenue. If your ad space has a high viewability score, it’s likely going to be more valuable to advertisers. In turn, you can charge a premium price for these spots.

Why Ads Lose Viewability

There are a few different factors that affect ad viewability. By understanding how ads lose “actual impressions,” publishers can find ways to combat the loss and boost their score. Below, we mention four of the most common causes of viewability issues.

Too High Above- or Below-the-Fold (ATF and BTF)

One of the top reasons ads lose viewability is their location, particularly if you frequently use below-the-fold placements. Naturally, publishers would want to monetize the bottom half of their pages to generate more revenue. However, not all visitors get that far, so the ads are delivered without being seen.

Source: Marketing Tracer 

If you think you can compensate by putting ads at the top of your page, think again. Data suggests that users scroll down too quickly for these ads to generate the 1-second impression that counts as viewable. That’s why publishers need to evaluate the scores of their ad placements and make optimization decisions accordingly.

Ad Blockers

A significant number of people use ad blockers to avoid intrusive, annoying advertisements. Unfortunately, that impacts all publishers, including those that follow best practices and prioritize user experience. A blocker identifies and hides ads before a user can see them. While some networks still register the blocked ad as an impression, it isn’t actually viewed, which negatively impacts your viewability score.

Non-Human Traffic

Web crawlers, bots, link checkers, and other non-human technologies are designed to resemble normal browsing behavior as much as possible. When they visit your site, they may generate an impression. However, since an actual human didn’t view the ad, your score is affected.

Bounced Users

When a user visits your site but leaves before it’s fully loaded, it’s called a “bounce.” Typically, one in every four visitors will leave your page if it takes four seconds or more to load. Loading speed is just one of many factors that impact your bounce rate, but the consequence is the same. While an ad may be delivered and an impression registered, the ad won’t be viewed, dropping its viewability score.

Here’s How You Can Improve Ad Viewability

While there are several ways you can improve your ad viewability, we’ve mentioned a few of the common methods you can use below. We’ve found that these strategies usually have excellent results – if you implement them correctly.

Improve Ad Placements

For the best results, try to focus on placing your ads above the fold (ATF) but not so high that users quickly scroll past them. Also, keep in mind that ATF won’t necessarily be the same for all users since their device and screen size can affect the ad’s position.

Instead of arbitrarily choosing a spot on the page, use scroll depth to see where users spend the most time. Target those spots for your ad placements.

Optimize Ad Sizes

According to a data report by eMarketer, some ad sizes perform better on mobile, while others get better results on desktop. For mobile, the optimal dimensions are:

  • 120x240
  • 240x400
  • 234x60
  • 320x50

For desktop, use the following sizes:

  • 970x250
  • 300x600
  • 728x90
  • 300x250

While these dimensions are a good starting point, always evaluate the performance of your own ads to see what works and what doesn’t.

Reduce Your Bounce Rate

A high bounce rate is a symptom of many problems, including design, loading speed, content quality or relevance, and more. If you’ve determined that a high bounce rate is one of the problems affecting your usability score, you’ll need to figure out why users leave your page without interacting with it. Once you fix the problem, the rate should fall, and your ad viewability should rise.

Lazy Load Ads

Instead of loading an ad the moment a user lands on your page, consider using lazy loading. That way, the ad won’t be loaded until it’s in view on the screen. It’s a great way to improve your viewability score without too much effort.

Use Sticky Ads

A sticky ad will remain visible as a user moves through your website. For example, you can have an advertisement displayed in a sidebar beside your content. As a user scrolls down to read, the ad will move down with them, keeping it in view. Keep in mind that if they’re too large or if you use too many, they’ll start to annoy your users, and you risk alienating your audience. Always use sticky ads in moderation.

Only Use Ad Refresh on High-Viewability Ads

Publishers have been using ad refresh to increase their Session RPM, and it can be a very powerful, revenue-boosting tactic. However, using refresh on ads with low viewability can have a significant negative impact on your score. Ensure that your ads only refresh after they’ve met your network’s standard viewability criteria to improve your score.


Ad viewability isn’t just important; it’s a critical metric to which every publisher should be paying close attention. The advertising industry isn’t likely to change its stance on viewable impressions, and publishers who can show top viewability scores are more likely to get high-value bids and direct deals.

Filipe is a Senior Business Analyst focusing on Pricing & Yield at Softonic. As a Senior Business Analyst, Filipe is responsible for maximizing the revenue yielded from the traffic generated by all our properties, including rev•amp, Softonic’s new publisher monetization platform. Within rev•amp Filipe oversees the pricing strategy, as well as being on the constant lookout for opportunities to improve monetization capabilities.
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