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How to Improve Ad Viewability: A Quick Primer for Publishers

Did you know that an average publisher’s viewability rate is 57.3%? This means that the remaining 42.7% of ads are never seen. Placing ads on a website doesn’t necessarily mean users will see them. There could be numerous reasons that can obstruct users from viewing the ads. So, how to improve ad viewability to ensure your ads are actually seen.

Over the years, Google has raised the bar on evaluating ad performance; viewability being one of the most relied upon metrics now. Publishers should realize that viewability has a direct impact on ad revenue and start acting on it seriously.

The topic of ad viewability has been around for a while, but most publishers are still not aware of its importance. In this post, we will explain the most effective methods that publishers can use in order to improve ad viewability. Let’s get started!

Understanding Ad Viewability

Viewability defines whether an ad (web ad or mobile ad) had the chance to be seen by a user or not. For instance, an ad placed at the bottom of a webpage may not be deemed viewable if a user does not scroll down far enough to reach that ad.

Publishers with a high viewability score are often regarded to have high-value inventory. Buyers are open to making relatively higher bids for such inventory since they know that their ads will have a high chance of being viewed.

As with anything else, measuring ad viewability is the first step to improving it.

So how do you measure ad viewability? As per Google, display ads that are 50% in view for at least one second are counted as viewable. Similarly, video ads that are 50% in view playing for at least two seconds are viewable. Google calls viewable impressions “Active Views”.

Publishers should keep a tab on their viewability score. The purpose is not confined to just achieving an impressive viewability score, it is to improve value for advertisers by maximizing the ROI on their ad spend.

How To Improve Ad Viewability

  1. Test Ad Positions, Sizes, and Layouts

    The most viewable ad position is not when placed anywhere on top of the webpage but right above the fold. Placing the right ad size in the right position makes it even more effective. Certain ad sizes like 728×90, 300×250, and 300×600, along with vertical sizes like 120×140, 240×400, 160×160, and 120×600 are considered the most viewable.
    Vertical ad units are known to be more viewable as the length of these ads keeps them in the viewport even as users scroll through the page. Ad formats like Sticky ads and Docked ads also help in achieving better viewability by sticking to the user’s screen; these ads are desktop compatible.
    Moreover, A/B testing different ad layout variants (=combinations of certain ad sizes and positions) helps make a data-backed decision about which layout works best and which does not. The winning layout is the one which keeps users engaged for longer without hampering their experience with the website.

  2. Fix Page Load Speed

    Poor page load time is one of several reasons why most ad efforts fail. If the page doesn’t load in time and the users bounce off the page, that means a decline in viewability score. But thankfully, there are ways to optimize resource loading and improve viewability. Here they are:
    Lazy loading renders content and ads only when they are in the user’s viewport. This helps increase viewability by decreasing the number of impressions served out of the view.
    Asynchronous loading using Google Publisher Tag (GPT) API and AdSense tags make ads load independently of other page resources, this reduces bottlenecks during page load.
    Minimizing passbacks means reducing the number of ad calls made from one server to another via passbacks. Fewer ad calls mean faster loading and hence better viewability.

  3. Analyze Devices and Channels

    Different publishing channels and devices score uniquely on viewability based on factors like traffic volume on that channel, level of user engagement, number and frequency of ads, among others. For example, viewability for display ads may be best on a mobile responsive blog.
    Similarly, video ads may get the best viewability score as YouTube ads compared to web or app-based ads. Analyzing the channel-wise viewability and comparing this data to create ad layouts can be a smart method to focus on the channel and device that get you the best results. 

  4. Optimize for Mobile

    With the rising share of mobile traffic, it is more important than ever to optimize ads for mobile. To begin with, here are some small tweaks that can help improve viewability for mobile ads:
    Replace 320×50 ad units with 320×100 unit size. This size is the large banner for mobile devices and works best when placed just above the fold. Optimizing placements as per different screen sizes prove to be an add-on for improving viewability. Your Google Analytics can show you the most used device by your users.
    Add a 300×250 ad unit to the mobile website. This size is generally a fit for all mobile screens. Placing this ad unit just below the fold is known to meet viewability criteria often. Moreover, this ad size gets high fill rates as most advertisers/buyers prefer to include this size.
    Prevent accidental clicks by adding space between content and ads. Doing this will help improve user experience, alongside optimizing viewability. Moving the ads 150 pixels away from the content elements of your webpage should be a good start to test how it works. 

Final Thoughts

Working on improving ad viewability is crucial to gradually improve inventory quality and ad revenue. The levers of ad viewability are testing on the ad unit level, fixing page-level issues or lags that cause latency, and finally optimizing the site by A/B testing or a complete design overhaul.

In order to streamline effort, the viewability cycle can be segmented into three stages:

  1. Measuring一find the number of Active Views you are getting against the total number of impressions you served during a given period.
  2. Analyzing and planning一create a blueprint of methods you can use to improve viewability and their respective steps that you need to execute.
  3. Executing一once you have a plan in place, start executing the plan and wait until you have substantial data to help you decide your next steps.  

It is important for publishers to understand that viewability is not an engagement or revenue generation tactic. It is about technical rendering and delivery of ads on the website to ensure that publishers are making full use of their inventory.


1. What Does Ad Viewability Mean?

Defining ad viewability, the IAB defines viewable ads as those with at least 50% of their pixels in the user’s view for longer than one second. Google and other digital advertising actors support this definition. The viewability rate is the percentage of viewable ads.

2. What causes low viewability?

The primary reason for low ad viewability is that pages can load before ads. The user sees a white space, and scrolls past it. After the ad loads, it registers an impression, but the user never sees it.

3. How do you calculate viewability?

By calculating the viewability rate, you can determine how many people saw your ads. This will allow you to identify partners and ad formats that will help you reach your campaign goals. By dividing the viewable ads by the measured ads, you can calculate the viewability rate.


  1. This is a well-written article about ad viewability. I thought for once this is not very popular among publishers but then just discovered how important it is for publishers to take their viewability seriously. Some of the factors mentioned and discussed here are very important and could help increase viewability rate of publishers. Use it for your advantage publishers.

    • Peerielmedia9ja Reply

      Wow…. Thanks for this great content… Am very much satisfied with what am searching for… I will Surely do as you said.. Thanks

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