Anchor ad vs sticky sidebar: the same 300x250 in two homes

Anchor ad vs sticky sidebar: the same 300x250 in two homes

Benchmark drop. Revenue per slot, identical demand (n=85 sites):

— Mobile anchor (bottom) $▮▮▮▮▮▮▮ highest viewability 91%
— Sticky sidebar (desktop) $▮▮▮▮▮ viewability 74%
— In-content static $▮▮▮ viewability 58%

Anchor units print the best viewable RPM but eat into Core Web Vitals if not reserved with min-height. Sticky sidebar only works above 1024px and competes with your own content for attention.

The sneaky cost: anchor + sticky sidebar together trip some advertisers' brand-safety density caps, suppressing premium bids. Run one anchor, not stacked stickies.

So what: Single mobile anchor vs stacked stickies — premium fill ▲ 9%, CLS penalty ▼.