A waterfall is the traditional ad serving model: your ad server offers each impression to demand sources one at a time, in priority order. If the first demand source does not fill the impression, it passes to the second, then the third, and so on. The winner is whichever source in the queue first meets your floor price. The problem: this approach favours whoever is highest in the queue, not necessarily whoever would pay the most. A buyer prepared to bid ₹500 sitting in position 4 loses to a buyer bidding ₹200 in position 1.
A unified auction (the CTV equivalent of display header bidding) lets all eligible demand sources bid simultaneously. Every buyer sees the impression at the same time, submits their best bid, and the highest bid wins. This produces genuinely competitive dynamics and typically results in higher clearing prices than waterfall — particularly when multiple buyers want the same inventory.
In display, the industry moved from waterfall to header bidding (unified auction) over 2015–2020. CTV is following the same path but more slowly, because the technical implementation is different: CTV uses server-side ad insertion (SSAI), which makes simultaneous demand calls harder to manage than client-side display header bidding. Most mature CTV monetisation platforms have moved to unified auction frameworks, but India's mid-tier CTV publishers often still use waterfall-based configurations — partly because of infrastructure constraints and partly because SSP support is more limited.
If you are an India CTV publisher currently using waterfall architecture, the yield opportunity from moving to a unified auction structure is real — but only if you have sufficient demand competition to benefit from it. A unified auction with two bidders produces minimal uplift over a well-managed waterfall. Build demand breadth first.
Full guide
For a complete explanation, read: Unified auction vs waterfall in CTV ad serving: which earns more for India publishers?