Why Ad Viewability Is Important For Programmatic Success


Ad Viewability is a metric used to measure how many impressions are actually seen by users. According to the IAB (Interactive Advertising Bureau) standards, at least 50% of the banner or creative must display on screen for one second or more to be considered a viewable impression. For video ads, that increases to two seconds.


Put simply, ads that are not viewed have no value to advertisers. Viewability metrics are used by demand partners to make decisions on CPM and target specific inventory that matches certain view rate criteria. Generally, the higher the viewability score, the higher the CPM will be, although that’s not the case 100% of the time.

Let’s put it this way: 1000 impressions at 50% viewability means that 500 of those ads have actually been seen by a user (or at least should have been). That doesn’t say anything about their quality, it just measures how many were delivered to actual people. Let’s imagine you’re bidding a CPM of 1$ for those same impressions. You would basically be paying $1 for 500 ad views instead of 1000. At 70% view rate that would be 700 impressions and so on. So, higher the viewability is, the more real ad views advertisers get for their money.

However, with high scores competition increases as well, which drives prices way up. That doesn’t always make financial sense for advertisers, which means that viewability and performance don’t automatically go hand in hand. It really comes down to how valuable that inventory is in the first place, with view rate being basically a modifier to that price tag.

The good news is that some campaigns, such as brand awareness ones, can actually use viewability as their key KPI. This means that view frequency does quite often lead to high competition and respectively better yield. Monitoring for and identifying such campaigns is critical to maximizing your ad income via viewability.

In the end, marketers’ goals are to drive some sort of action from their ads, be that clicks, sales or form submissions etc. Viewability is only one piece of that puzzle, albeit an important one.


There is a slight difference between how viewability is measured on the buy-side and the sell-side. For publishers, however, the most common option by far is the Active View report in Google Ad Manager. It’s a free and transparent tool accredited by the Media Rating Council (MRC) that’s readily available on the platform. Active View tracks and measures the viewability of display and video impressions across the web and in-app served. Not every impression can be measured, but overall the report is pretty accurate and gives you information on how many impressions out of all eligible have been viewed, as well as for how long.


Ad viewability can be affected by many decisions a publisher may make, as well as user behaviours.

Good site design is integral to shaping the strategy and performance of digital advertising. Page design and length should help decide ad layout, size and position. For instance, ATF ads are usually more viewable than BTF ones, with the most viewable spot on average being right on the BTF break line. Generally speaking, view frequency scales down the longer the vertical distribution of content is. Shorter content pages tend to have higher overall viewability rates because of this. However, longer pages that drive good retention and scroll depth will likely see less of a difference between ATF and BTF viewability too.

Ad size also plays a role in viewability, but ironically the actual size doesn’t matter that much. Instead, what’s important is the ad’s aspect ratio. With 50% of a banner required to be on screen, it really comes down to the ad’s midpoint and its placement to define viewability.

Certain sizes and aspect ratios offer more flexibility in terms of positioning, which specifies their performance. For example, horizontal ads are more frequently placed in ATF sections, hence why they show better viewability on average. On the other hand, vertical placements are the most popular choice for sidebar implementation and stickies, which is why their time on screen is longer across the board.

Another important factor that plays into viewability is site and ad speed. A page crowded with ad formats and heavy setups will have a poor load speed and result in ads not being displayed within the time a user is engaged. If they scroll away before the ad has loaded, then the viewability rating will be lower. 

Last but not least, there are some popular ad delivery functions that also have an impact on view rate such as auto-refresh and lazy loading. This category of scripts and products is quite diverse, and so are the possible outcomes in terms on viewability. It comes down to how the tool you use exactly works, so make sure you have an in-depth understanding of anything that’s added to your ad delivery before it goes live.


Viewability is an integral cog in the programmatic ad trading machine, which is why we build our Smart View and Smart React products, giving publishers superior control over their front end. Smart View takes automatic ad injection and lazy loading to the next level, creating true 100% viewable inventory dynamically, responsing to user engagement and keeping a clean UI. Smart React on the other hand is a new type of ad refreshing technology, that investigates user behaviour to only reload ad units when they have been seen for an absolute amount of time.

Get in touch with us to find out more about our Smart product range and book a demo.