Impact of lazy loading on performance

Lazy loading ads is a technique that lets you serve your users ads in the moment just before they are set to view them. As your user scrolls down your webpage and approaches the ad slot, an auction is triggered in the header and serves the winning ad only when the user reaches that ad unit on their device’s viewport.

Many websites are programmed to load the entire web page as soon as a user arrives, which means the site makes multiple HTTP calls/requests to the server to render all the elements on the web page. By trying to load all of the media at once, your page speed is impacted and it provides a poor user experience. 

Rather than loading all your ads at once, lazy loading allows you to decide what ads you would like to load on the initial page load, and which to load in real-time for the user as they scroll down the page. This reduces your page load time and improves the ad load speed and performance of your page. We suggest using lazy loading on units below the fold on your website, as you don't want to impact the performance of ad units above the fold. 

We worked with several publishers to increase their viewability by implementing lazy loading. We found a 63.56% increase in overall viewability and a subsequent correlation in the rise of CPM. Though you may see an increase in metrics such as viewability, you could see a slight decrease in impressions per session as users may leave prior to reaching the end of the page. But this can also help increase the value of the impressions, as demand partners are willing to pay higher CPMs for impressions that are more likely to be viewed by a user.

If you are interested in talking with a Freestar Ad Ops expert about how we can help you optimize your advertising revenue, please fill out a request for demo. We would be happy to chat with you. If you are an existing customer and need help optimizing viewability or implementing lazy loading, reach out to your Account Manager or email

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