Viewability best practices

Improving ad viewability on the site- 

Best practices to improve viewability of ad units on the site have been discussed below with a logical reasoning and/or available data.

IAB, MRC, Google, Integral Ad Science, and couple of other players in the digital ad industry have released primers, guidelines, and best practices, some backed by data, others by logical thought and intuition, I have tried to combine most of these here but I would highly recommend anyone reading this to not just blindly follow these as they aren’t rules but suggestions and take a data driven approach instead.

Obviously, if the ads are going to be more viewable, it means that the likelihood of a user coming across one would increase, hence, you wouldn’t want to just shove an ad down the viewers throat, cause at the end “User is the King!”, so data driven approach to viewability doesn’t mean looking at the viewability numbers in isolation but also measuring visitor behavior on the site (increase in adblock user % or feedback regarding ads). The end goal is to make ads work for everyone.

Measurement is at the center of the ad viewability improvement process as improvement of measurement rates (measurability) and ad latency directly affects viewability. Benchmarking, Analysis, Planning, Execution & Iteration are milestones on the road to viewability improvement.

Now let’s discuss the basic factors that influence ad viewability in greater detail-


4 factors affecting viewability

Engaging Content

Content is at the soul of the site and it’s fairly obvious that quality content drives better viewability.


Site Re-Design

  • Ad Size

Vertical ad units tend to perform better on the viewability scale because returning users are familiar with the site layout and often scroll directly to the content on the page, easily skipping the horizontal ad units. Double MRecs perform the best, followed by Skyscrapers and larger rising star units (Billboard>Portrait)

  • Ad Position

Position plays a very important role and if done right, can help boost viewability and revenue numbers considerably. However, these ad position changes should be in accordance with the best practices like avoiding accidental clicks and bad user ad experience.

Look beyond the conventional ad placements you see on most sites and focus on areas of the site where your user has the maximum dwell time.

Running contextually relevant ads wrapped around content ensures higher ad viewability and engagement. Advertisers are usually averse to booking ad positions at the bottom of the page, publishers can ensure that engaging content on their website is well distributed all over the page, including at the bottom(sign up, call to action or access to similar content) to improve bottom ad viewability.

As discussed above, vertical ad units are more viewable while horizontal sizes tend to be easily skippable unless placed properly. Try placing Horizontal ad units just above the fold where they tend to have the highest viewability just above the fold.

  • Responsive

Responsive site layouts can be used to optimally display site content and ad units on different types of devices which helps the audiences to engage more and as a result viewability rates go up. Responsive ad unit strategy should take in account active viewport changes due to browser resizing or orientation changes.

  • Refresh

Page refreshes should be avoided unless absolutely necessary. If there’s some content on the page that can be updated without refreshing the entire page, that’s the best. If you need to refresh ad units, in cases when the user spends a lot of time on your page, you can choose to refresh ad unit alone, only when it is in-view. This drives higher viewability and value for the advertisers and a better experience for the user. Ad unit refresh time should be a data driven decision as a quick refresh often results bad user experience and can also adversely affect your viewability score.

  • Page Scrolling

Depending upon the amount of ancillary content and the importance of displaying that during video playback we can

  1. Only play back video in full screen mode
  2. Lock the video player window into the viewable screen area and only scroll the ancillary content, not the video player.
  • Out of focus tabs/windows

We all multi-task and have at least a dozen tabs on our browser at any point of time, due to which viewability rates suffer, hence it is best not to refresh ads when the ad unit is not in the active viewable area on in-focus tab/window. In the case of video, pausing the video playback helps solve the problem.


  • Ad latency

Viewability measurements start once the ad has been fully rendered, hence latency pertaining to the ad render time has a direct impact on the viewability of an ad.

Ad latency can be reduced by simplifying partner stack and establishing an ad timeout for the RTB partners. Ad Latency can also be avoided by instituting asynchronous ad call setup and using your most profitable partner as your ad serving platform to maximize the potential of your inventory.

  • Page latency

Page latency is a grave issue, especially on mobile, and affects digital publishing and advertising directly. Ads should be loaded asynchronously to improve user experience and reduce page load time.

Also, a large number of ads and additional tags on the page, slow down page load – leading to a user abandoning the website, installing ad block and poor viewability. Removing ads with poor viewability rates will not only help you improve the user experience on your site but also reduce ad clutter rates (an advertiser KPI).


Ad Tech/Ops strategy & policies

  • Lazy loading

This is a content retrieval method that only loads content and ads on the BTF page section when they are in view, or that are about to be viewed. When implemented correctly, it results in faster page loads and better viewability of below-the-fold ad units. These changes directly affect the user experience and hence should be implemented carefully after beta testing on certain sections of the site.

  • Iframes

An Iframe is an HTML document embedded inside another HTML document. Ad tags within some iFrames, such as cross-domain iFrames, can’t be measured by any viewability solution so we should avoid these hostile frames and use friendly ones instead.

  • Ad Formats

Rich Media/Video driven ads usually have heavier creative assets which lead to ad latency. You need to evaluate the opportunity and formulate an implementation plan based on factors like CPM lift, the device (formats available for desktop, tablet and mobile), user experience and viewability.

The sticky unit is a commonly used ad format across desktop, mobile and video. It scrolls with the user for a few seconds to ensure high viewability for this unit. Potentially intrusive, this unit should be implemented with care to avoid accidental clicks and a bad overall user experience.

  •  Creative size and Timeout limit

We should establish creative size and timeout limits for all RTB as well as direct partners, especially for the ones with higher viewability demand.

  • Minimizing Passbacks

Ads load more slowly when ad calls are passed from one ad server to another via passbacks. Fewer passbacks would mean faster ad loads and higher viewability rates.


It is crucial to better understand your site’s inventory to improve upon these metrics and package inventory more effectively to appeal to the advertisers looking at brand exposure as well as viewability.

Want to know more? Check out my other article, which covers the basics of viewability.

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