What is a publisher waterfall in CTV advertising?

A publisher waterfall is the priority order in which a CTV publisher's ad server considers different demand sources when filling an ad break slot. When a viewer reaches a break, the ad server does not simply run a single open auction — it checks demand sources in sequence, starting with the highest-priority commitments. A typical India CTV waterfall: (1) Programmatic Guaranteed deals — firm impression commitments with locked CPMs; (2) PMP deals — invited buyers bidding in a private auction above the floor; (3) Direct IO campaigns — managed delivery against contracted placements; (4) Open exchange bids from SSPs; (5) House ads — publisher's own promotional content if nothing else fills. The slot goes to the first demand source that produces a winning bid meeting the floor or reservation price.

PMP underdelivery in India CTV has four common causes: (1) Programmatic Guaranteed demand consumes slots before the PMP sees them — PG deals have higher waterfall priority than PMPs. If PG campaigns are active and well-paced, PMP inventory is genuinely limited. (2) The PMP floor CPM is higher than what the buyer is bidding — the deal passes bid requests but bids are consistently rejected because they fall below the floor. Check the deal's floor price and set line item CPM bids at or above it. (3) The PMP inventory package is smaller than estimated — the publisher's description of "premium sports CTV" may map to fewer eligible impressions than expected. (4) Line item targeting is too restrictive — the deal sends bid requests but they are excluded by the buyer's audience or geographic filters. Widen line item targeting and recheck delivery.

Traditional waterfall architecture is sequential — demand sources are checked one at a time in priority order. Header bidding runs parallel auctions across multiple demand sources simultaneously, letting the publisher choose the highest bid from all sources at once rather than stopping at the first one that clears the floor. In web advertising, JavaScript header bidding runs in the browser. In CTV, there is no browser — header bidding happens server-side (SSHB, server-side header bidding). PubMatic's OpenWrap and Magnite's header bidding product are used by some India CTV publishers to implement SSHB, increasing competition for each impression and potentially improving publisher yield. The impact for buyers: fairer access to inventory based on CPM rather than waterfall position, but higher effective CPMs as more buyers compete in a unified auction.