Ad Viewability | What is It and How to Improve It?

Ad viewability

Last year in the US, ad viewability levels increased across all formats to almost 70%.

Both publishers and advertisers are striving to increase their ad viewability rate. In this article, you will learn what ad viewability is, why is it important, and how to improve it.

Table of Contents:

What is Ad Viewability?

Ad viewability is a metric used in digital advertising to measure how visible the ads are on the publisher’s website to users. According to the Interactive Advertising Bureau’s (IAB) standard, for an ad to count as ‘viewed’, 50% of it must be visible to a user for at least 1 second. For video ads, 50% of the ad must be visible for at least 2 seconds. Google refers to viewable impressions as ‘Active View‘. 

How to Measure Ad Viewability?

To measure ad viewability, you have to find the total viewable ad impressions served and divide by total ad impressions served.

Viewable impressions served– the number of times your ad impressions were considered viewable (you can see this metric in your GAM or any other ad server).

Viewable impressions allow publishers and advertisers to understand if the ad was displayed in a viewable position.

Why is Viewability Important?

If users don’t view more than half of the served ads, ad campaigns become ineffective, and the price is much less than for a viewable ad. So viewability directly affects the value and quality of the publisher’s ad inventory. Other additional metrics are also considered, such as viewable time, and user engagement adds an extra layer of clarity about the ad inventory’s value.

Currently, the programmatic industry focuses more on checking viewable impressions rather than served impressions. 

Here are few points that emphasize the importance of viewability:

  • Thanks to the IAB standard, ad viewability helps to ensure that advertisements are successfully delivered to the users. 
  • Ad viewability allows checking the performance of each ad placement.
ad viewability example
  • Publishers can better understand which ad placements perform the best in terms of viewability and have better revenue potential. Additionally, publishers can think of ways and techniques to improve ad inventory and optimize for better viewability.

What can cause a low ad viewability score?

  • Page length and quality of the content– according to Google, shorter content has higher viewability. Setting pages with a single fold allows users to get through content more easily. Also, if your content is not engaging enough, users might leave.
  • Slow load of ads– if your ads don’t load fast enough, users might scroll past them before they load, causing a drop in viewability.
  • Ad position– if the ads are placed below the fold, it can negatively affect the viewability.
  • Ad placements– some ad placements influence the viewability results, regardless of how fast they load or what banner format is used. For example, the top leaderboard would rarely have viewability above 50%.
  • User behavior on a website– if users don’t interact with your page long enough, it can create low engagement meaning that ads can be requested but aren’t served.
  • Internet speed– if the user’s internet speed is slow, ads might not load.


If the ad is placed at the end of a long article, we suggest publishers implement lazy-load mode. It will load the ad dynamically. The lazy-loaded ad will be displayed only when the user scrolls close to the ad placement at the bottom.

How to Improve Ad Viewability?

Consider the previously mentioned points and follow the tips below to improve the ad viewability rate.

  • Improve ad load speed

One of the most important factors that impact ad viewability is user behavior combined with the ad load speed.

This means that if your website is super fast, it actually might decrease the viewability. How? User behavior will change, and if the ads load slow, the viewability will drop. So, an actually fast website may not improve viewability; your ad loading speed is what matters.

How do you improve ad load speed?

1. Implement lazy loading. This will reduce overall page latency and improve viewability. Lazy loading allows delaying load for various page elements (images, ads, and iframes). The concept is simple–an ad request is triggered right when the user is most likely to see it. 

Google states: “If used properly, lazy loading can increase the overall viewability percentage. In cases where a user doesn’t scroll down, for example, the below-the-fold ad slots don’t load, and fewer ad requests are made. However, if the ad size is too large or loads too late, for example, when the user scrolls down faster than the ad loads, the user won’t be able to view the ad.”

2. Minimize passbacks. This will reduce the number of ad calls made from one server to another. Fewer ad calls will load your website faster and improve ad viewability. 

  • Implement ad refresh

Ad refresh allows reloading ads if they are in view for some time. This will guarantee that the new ad will be visible immediately after rendering it. Also, this will increase your ad placement’s viewability score in your ad server and get more ad impressions, thus increasing ad revenue. 

But don’t get carried away and let the ad show for at least 20 seconds, so the user can actually notice it and hopefully click on it. A high ad refresh rate will lower your CTR score. At Setupad, we have an ad refresh called Viewable Bid Optimization–this feature can take care of the optimal ad refreshes for your site.

  • Get more familiar with your audience behavior

When you understand on which pages users spend most of the time and engage with the content, you can decide how many ads you should serve. Usually, monetization companies, like Setupad, can help you and suggest the optimal number of ads on your page.

Related Article: How Many Ads Should I Put on My Website?

  • Choose best performing ad placements and sizes

Ad placements mainly influence ad viewability rate. According to a recent study by Google, above the fold (ATF) video ads, on average, have a 73% viewability score, compared to 45% for below the fold (BTF) ads. Based on these figures, the ideal viewability score you should be aiming for your page needs to be either the same as the industry average or slightly higher.

In one of the SEO office-hours hangouts, Google’s John Mueller explained that they want to see some content above the fold, meaning that a part of the publisher’s page should be visible when a user visits the site. This also means that ads shouldn’t exceed your content.

Final Thoughts

Publishers should continuously work on improving the loading speed of their webpage and user experience. The content of the website and the ads should both load at the same time but asynchronously. This will help to improve your ad inventory’s quality and increase ad revenue.

Viewability helps publishers to ensure that they can make full use of their inventory by serving ads.

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