Fill rate is the percentage of ad opportunities (impressions requested) that the ad stack manages to fill with a real, paying ad. An unfilled slot is lost revenue - and a bad viewer experience if it leaves a gap or shows a slate - so fill rate is a key health metric of the monetization stack.
It depends on demand: how many advertisers want this audience, how well the platform is connected to demand sources (direct deals plus programmatic exchanges), and floor pricing. There is a constant tension between fill rate and CPM - lowering the price floor fills more slots but at lower value - so optimizing ad revenue means balancing the two, often with fallback waterfalls or header-bidding-style auctions.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
Fill rate measures how many ad slots get a paying ad, and an empty slot loses revenue and leaves viewers staring at a slate. The seven volumes cover the video stack; for fill rate start with Volume 3 on players and the economics of streaming, then Volume 2 on manifests and ad markers, with encoding in Volume 1. Written by Nikolay Sapunov, CEO at Fora Soft.
Ad slots going unfilled and revenue lagging behind views?
We will audit your ad stack and player behavior and send a plan to raise fill rate with the expected revenue impact. 250+ video products shipped since 2005.
