Glossary
What is Waterfall?
Also called: daisy chain, waterfalling
A waterfall offers each impression to demand partners one at a time, in a fixed order based on past prices, until one accepts.
हिंदी में पढ़ेंIn a waterfall, the ad server ranks demand partners by their past average prices and calls them one by one. The first partner willing to pay at or above its floor takes the impression, and the rest are never asked. Each passback to the next partner adds waiting time.
The flaw is that yesterday’s averages decide today’s sale. A partner further down the list may value this impression more, but never gets the chance. Header bidding fixed this on the web by asking all partners at once, before the ad server decides, so the partner willing to pay most today can win.
The same idea survives in apps. Mediation waterfalls call ad sources one by one based on the eCPM you set, while bidding sources compete in a single real-time auction, and one mediation setup can use both. If your partners sit in a ranked list with fixed prices, you are running a waterfall.
Example
Partner A is first with a $2.00 floor and accepts at $2.10, so the waterfall stops. Partner C would have paid $3.00. That is $0.90 less CPM; across 100,000 impressions it would be $90 (100,000 × $0.90 ÷ 1,000).
Why it matters to publishers
A waterfall can leave money on the table and slow pages. Spotting one in your setup is the first step towards real-time competition.