<b>Second-price still lives inside your first-price world — and it leaks money</b>

<b>Second-price still lives inside your first-price world — and it leaks money</b>

The open exchange went first-price, but second-price pricing survives in pockets, and the mismatch between the two creates a quiet leak.

Where both coexist today:
— Many Private Marketplaces (PMPs) and some SSP server-side auctions still resolve as second-price internally.
— Header bidding wrappers may run a first-price auction in the browser, then pass the winner into an ad server that itself resolves another auction with different rules.
— The result is a chain where your bid is treated as first-price in one stage and second-price in another.

The leak: if you apply uniform first-price shading everywhere, you under-bid in the second-price pockets. In a true second-price auction the optimal strategy is to bid your full value — shading there just lowers your win-rate without lowering your average price paid, since you'd only ever pay the runner-up's bid anyway.

Diagnostic: tag each supply path by its actual pricing rule (ask the SSP; verify by checking whether your price-paid ever equals your bid exactly, the fingerprint of first-price). Then split your shading logic: aggressive on first-price paths, near-zero on confirmed second-price ones.

Why it matters: shading is correct medicine for first-price and a self-inflicted wound in second-price. One global setting across mixed auction rules guarantees you're wrong somewhere.