Dial in lazy-load thresholds: the test

Lazy-loading ads boosts viewability but, set too aggressive, fires the call after the user scrolls past — a viewable-but-unsold miss. Optimal threshold: load 150-300px before slot enters viewport (n=60 sites).

Threshold → viewability / fill
0px (on-enter) ▮▮▮ high viewability, low fill
200px (before) ▮▮▮▮▮▮ best net RPM
800px (early) ▮▮▮▮ low viewability, high fill

— Step 1: Set threshold to 200px globally.
— Step 2: A/B vs 0px and 600px for 14d.
— Step 3: Compare RPM, not viewability in isolation.

So what: 200px beats on-enter loading by ▲ 5% net RPM.