Case: lazy-loading ads on a 40-page recipe site

Case: lazy-loading ads on a 40-page recipe site

What it did: deferred all below-fold ad calls until the unit was 600px from viewport, native IntersectionObserver, no plugin.

— Setup effort: 2/5 (one GPT field + observer script)
— RPM lift seen: page RPM up from $11.40 to $13.20 (+15.7%) over 21 days, 38k sessions/day
— Why: viewability on the second in-content unit jumped 51% → 79%, so the unit cleared more bids

Pros: free, killed ~140KB of upfront ad JS, LCP improved 0.4s.
Cons: scroll-fast users sometimes saw a blank slot for ~300ms; we added a min-height placeholder to stop CLS.

Lift: ★★★★☆ — Risk: ★★☆☆☆
Verdict: do it, but only below the fold and always reserve height. Best for: content sites with deep scroll. Skip if your traffic bounces above fold.