Ad viewability is a highly impactful RPM optimization. You as the publisher should always consider it when making layouts and placing ads.

A display ad is considered viewable if 50% of it appears on screen for at least 1 second. A 2014 Google study revealed that 56.1% of measured impressions at that time had failed to meet that criteria. As you can imagine, advertisers didn’t appreciate that statistic and pivoted towards using ad viewability as a key performance indicator (KPI).

Since then, CPM display/video tracking technology has evolved to better accommodate the metric. For instance, Google now offers broad viewability targeting, as well as the option to only bid on viewable impressions.

An ever increasing amount of advertisers are filtering you out if your ad viewability is sub-standard. The good news is this is entirely in your control. Viewability goes up and down mainly based on your ad configuration and changes you make to your layout.

Refresh only when the ad is viewable

We recommend that you only automatically refresh ad slots if they’ll re-qualify as a viewable impression. If the ad isn’t on screen, wait to refresh until it is.

Lazy load off-screen ads

You should wait to load any ads on the page that aren’t on-screen. Load the ad when the user scrolls down and you’re confident the ad will soon be visible.

Watch out for Cumulative Layout Shift (CLS) when lazy loading ads. It’s a bad user experience if your content moves around as the user interacts with it (e.g. element that was 0px height suddenly has a 250px tall ad).

Avoid putting ads at the very top / bottom of your site

On your typical content-based layout, ads that are near the top of the page show markedly worse viewability than ads placed just above the fold. This discrepancy can be explained by users who scroll down past ads that haven’t finished loading.

Additionally, we see low viewability and very low engagement for ads put near the bottom of pages, even with lazy loading.

Use sticky ads in places that fit in your layout

Sticky positioned ads can be a good balance of keeping user experience impact low and hitting higher viewability benchmarks. Above all, sticky ads can be refreshed more reliably which increases the amount of viewable impressions your site produces.

Improve your page speed

The various assets that make up your page could be hurting your revenue in ways you haven’t fully considered. It’s a hit to your viewability if users scroll by ads that haven’t finished loading. You can’t control the speed and latency of your user’s internet connection, but you can take steps to make your page as optimized as possible for them.

Start by seeing how your site gets assessed by Google’s PageSpeed Insights. This tool provides diagnostics and direction on areas of improvement. After you’ve made optimizations, open DevTools (hit F12). Click the network tab and select “Fast 3G” throttling if Chrome or “Good 3G” if Firefox. This will allow you to emulate a slow internet connection while you browse your site to look for additional areas of improvement.

Don’t forget about mobile

All of the advice on this page applies on mobile. Nowadays, more than half of the people landing on your site are on a mobile device. Your design should be responsive, and your ad placements should be curated for mobile layouts.

How we help our publishers with their viewability

We regularly audit our publishers’ websites looking for opportunities to improve viewability. Having an experienced team in your corner takes the guess work out and saves you time. In addition to advice that is unique to your website layout, we offer several pre-built high viewability formats;

• “Sticky Stack” (try it). This unit loads new ads along a track as the user scrolls, and when they collide the older one is seamlessly pushed out of view.
• “Anchor” (try it). We highly recommend using this placement on mobile. Unlike sticky ads, these are fixed position on screen and always viewable.
• “Sticky Side Rail” (try it). This format makes it easy to run an ad in empty space along the left and/or right sides of the screen.