Load ads instantly, or only when scrolled into view?

Load ads instantly, or only when scrolled into view?

Eager loading runs the auction for every ad slot the moment the page opens. Lazy loading waits until a slot is about to appear on screen.

— Eager: ads are ready instantly, but you auction slots the visitor may never scroll to, wasting requests and slowing the page.
— Lazy: lighter, faster page, and you only spend auctions on ads people actually see, which advertisers love.

Tiny example: a 10-ad article eager-loads all 10 at once. Lazy loading might only ever run 4 auctions if most readers leave early, saving the rest.

1. Eager-load the first ad.
2. Lazy-load the rest, triggering ~200px before view.

In plain English: load the top ad now, the lower ones only when they're nearly visible.