The Complete Guide to Ad Viewability For publishers

Built with the expertise of:

Myles Engler, VP of Yield Optimization

Do visitors see the ads placed on your site? This is the question your viewability rating answers.

Viewability is one of the primary metrics by which advertisers gauge the value of your ad inventory. It tracks impressions and grades the ad unit based on how often the ad was actually seen by site visitors.

It makes perfect sense why an advertiser would use viewability as an indicator. An ad that isn’t in view has no chance of ever being clicked on (the advertisers’ ultimate end goal), so viewability is a great leading indicator for the ability to get a click-through. 

If visitors see your digital ads more frequently than not, your rating will be high. If they don’t, it will be low.

Here’s an example of what is meant by “viewable” —

If an ad unit is located lower on the page and a user doesn’t scroll far enough to see it, that means it was not viewable during that session.

Viewability is measured in percentages, but that concept breaks down when you talk about a single ad impression. Either an ad is viewable or it isn’t — it can’t be 70% viewable. A viewability rating tracks the likelihood of that ad being viewed. 

So a 70% viewability rating means that, historically, an ad was viewable 70% of the time and nonviewable 30% of the time. Because viewability is so heavily dependent on user behavior, there’s no way for advertisers to know if the ad they place there will be in the 70% bucket or the 30% bucket. But the higher the percentage, the better their chances.

That’s why advertisers pay more for ad units with higher viewability ratings.

What is a Viewable Ad?

The Media Rating Council has an established set of viewability guidelines to help advertisers and publishers align on standard practices.

Here they are —

• An ad must be at least 50% visible for a minimum of 1 second
• Display ads larger than 242,500 pixels must be at least 30% visible for a minimum of 1 second
• Video ads must be at least 50% visible for a minimum of 2 seconds

If an impression meets the above criteria, it counts as a view and increases your viewability rating.

Viewability Definitions

There are a few different ways to think about viewability. Here are some terms to know —

• Ad calls/ad requests: Each time a new session begins, a website will send an ad call to an ad exchange to request an ad unit for potential viewing. Depending on your site’s refresh settings, an ad unit may or may not be displayed multiple times within a single visitor’s session.
• Viewable impression: This metric demonstrates the frequency at which your ads were viewable. 
• Viewability rate: This percentage summarizes how many of your impressions were viewable.

Because it’s important to advertisers. 

All advertisers have the same end goal: to reach the right audience at the right time with their ads. If your ad isn’t viewable, the chance of securing a click or video completion is zero.

So low viewability means a low chance of delivering positive results for advertisers. Would you buy a ticket to the ballet if there were only a 30% chance you’d be able to see the stage? Advertisers want to feel confident that they’ll get what they pay for. And viewability is a good way to establish that trust.

That’s why viewability is one of the primary metrics you should be reviewing to understand if and where there is the most value for advertisers to show ads on your site. The more viewable ads you have on your site, the higher the likelihood of a positive outcome for advertisers. Better outcomes for publishers mean a better chance quality media buyers and brands will continue to advertise on your site.

Plus, when advertisers crunch the numbers, higher visibility ratings will result in an increase in ad spend on your units.

So high viewability rating = a better fill rate and higher CPMs.

And higher CPMs = more $$$ in your pocket.

Although there is an increasing demand for 100% viewability, in general, you shouldn’t think about it in black and white. Ads are rarely 100% or 0% viewable. We recommend novice publishers aim to have an ad viewability rate of between 60% and 70%, but keep in mind your sweet spot for viewability will be highly dependent on the value advertisers place on the makeup of your audience as well.

However, improving ad viewability isn’t a simple process. It’s a strange concept to understand — since they are directly connected — but viewability and revenue can actually be considered opposite forces. Stay with us on this one.

In general, to increase viewability, you need to decrease impressions and requests. Reducing those will ultimately result in less immediate revenue. But it’s important to keep in mind that optimization often means finding a delicate balance between viewability and revenue. This balance is unique to each publisher. Sometimes, you may have to sacrifice viewability to earn revenue and vice versa.

Think of it like an auditorium: the more tickets you sell, the bigger your venue needs to be. But there’s a catch. The bigger the venue is, the less valuable your seats are, since so many of them will have a poor view of the stage.

It’s the same with ad units. The more you have on your page, the less valuable they become. And if you have too many ads, there could be long-term harm to your engagement and user experience, and as a result, your viewability.