October 21, 2026 · CTREX Team
Smart Lazy Loading: Why Ad Banners Shouldn’t All Load at Once
Not every ad unit needs to load at the exact same moment as the page itself.
When a user opens a website, the browser begins processing text, images, styles, scripts, and ad requests. If all ad units load simultaneously, they can compete with the main content for network and processing resources.
The result is potentially slower page load times, delays in user interactions, and poorer performance metrics, including those from Google PageSpeed Insights.
The solution is Smart Lazy Loading, or deferred loading of ad units.
How does Smart Lazy Loading work?
Instead of loading all ads at once, the system loads each ad unit as it approaches the visible area of the screen.
For example, a banner can begin loading when the user is about 100 pixels away from it. By the time the user reaches the ad slot, the content may already be ready to display.
This approach helps avoid wasting resources on ad units located far beyond the current screen and distributes the load more efficiently.
However, the 100-pixel distance is not a universal rule. The optimal threshold depends on connection speed, device, ad block placement, and the time required to fetch the ad. For some placements, it makes sense to start loading earlier.
Why is this important for publishers?
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Less load at startup. The browser can focus on critical content rather than loading all ad elements at once.
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More efficient use of resources. If a visitor doesn’t scroll down to the lower ad units, some unnecessary early requests can be avoided.
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Potentially better performance metrics. Reduced competition for resources can positively impact load speed and user experience. However, the result depends on implementation and other site factors.
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A balance between speed and monetization. Properly configured lazy loading allows ads to be ready by the time they enter the user’s viewport, without loading the entire ad inventory at once.
How do you find the right loading point?
It’s not enough to simply defer all requests. If a banner starts loading too late, the user may see an empty ad slot or not see the ad at all.
Therefore, it’s important to test the loading threshold and monitor page speed, viewability, fill rate, and ad revenue.
Smart Lazy Loading isn’t about sacrificing ads for the sake of speed. It’s about managing when ads load so that the website uses resources more efficiently while maintaining a comfortable user experience.