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February 20, 2026Ad ServerNew Feature
UNIFIED AUCTION FLOW
YOUR SELLERS
▶
TOPSORT
AUCTION
UNIFIED POOL
◀
CRITEO
▼
HIGHEST BID WINS
Global A$1.55
Why We Built ThisMarketplaces shouldn’t have to choose between demand sources. Demand mediation lets third-party bids compete directly against Topsort demand in a unified auction — more competition means higher fill rates and more revenue per impression.

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The Problem

Topsort auctions previously only accepted bids from Topsort sources — vendors within a marketplace or via Toppie. If no Topsort demand existed for a placement, that ad slot went unfilled. Marketplaces with existing relationships with platforms like Criteo had no way to bring that demand into the same auction.

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The Solution

Demand mediation extends the auctions API to accept bids from external demand sources. The marketplace fetches bids from a third-party platform and passes them into the Topsort auction via a new demandSources parameter. Topsort compares all bids — internal and external — and the highest bid wins. Unified auction. Topsort and third-party bids compete in the same auction. No separate waterfall logic needed. Higher fill rates. When Topsort demand is low, external bids can fill the gap. More revenue. When both sources have demand, competition drives bids up. Criteo first. The first integrated source is Criteo, with support for additional demand sources via the same demandSources parameter.

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How It Works

1

Fetch external bids

On page load, the marketplace fetches bids from Criteo (or another demand source) for the placement.
2

Pass bids to Topsort

Include the external bids in the auction request using the new demandSources field.
3

Topsort runs the auction

All bids compete. The response indicates the winning source — "topsort" or "criteo" — for each slot.
4

Report events

For external winners, report events to both Topsort and the external platform.

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Who Should Use This

Large US marketplaces. Major brands bid on retail media via tools like Pacvue and Skai, which bid on Criteo inventory — this unlocks that spend without direct brand integrations. Large LATAM marketplaces. Criteo has significant presence in Latin America, making this a natural fit. Any marketplace with existing Criteo relationships. If you already have a Criteo account, adding demand mediation is straightforward.

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API Changes

The auctions endpoint now accepts a demandSources array with external bids (up to 100 per request). The response includes a demandSource field on each winner indicating whether it came from Topsort or an external source. For full implementation details, API examples, and error handling, see the Demand Mediation documentation.
Available now for eligible marketplaces. Contact your Topsort account manager to enable demand mediation for your account.