Antoine Mercier

Antoine joined Criteo in early 2017, the year the European retargeting business was running out of third-party-cookie runway and nobody at the conference circuit was willing to say it out loud. He started on the demand side — bidstream economics, retargeting curves, the supply-path math that determined which exchange Criteo paid to win the same user back — and within two years was on the team writing the company's internal answer to "what do we do when ITP 2.1 ships." The answer involved a lot of bidstream metadata that wasn't documented anywhere, and a lot of meetings where the legal team told the product team to remove sentences from the documentation.

In 2021 he crossed the table to Smart AdServer (the Paris-HQ SSP, since rebranded Equativ under Bridgepoint), where he spent three years on the supply side — header-bidding deployment for tier-1 French and DACH publishers, first-price auction migration, bid-shading audits, the Sharethrough merger announcement of June 2024 from a closer vantage point than he wanted. What he learned across both sides isn't in any whitepaper. It's in the gap between what header-bidding setups claim to optimise (advertiser yield) and what they actually optimise (the SSP's win-rate on its preferred deal-ID, regardless of CPM). It's in the auction-dynamics math behind first-price vs second-price bid shading, which most demand-side platforms still mis-implement in subtle ways three years after the format changed. It's in the difference between "viewability" as the IAB MRC defines it (50% pixels / 1s display) and "viewability" as a tier-1 French publisher measures it on a property that runs lazy-loaded sticky ads above the fold.

He left Equativ in May 2024 after the third reorg in eighteen months. The writing started as auction-log post-mortems he was sharing with two ex-colleagues, became a private Slack he ran for six months, and is now this site. He still consults — usually on header-bidding migrations and on bid-shading audits for advertisers who suspect their DSP is leaking money. He still reads the Prebid.js commit history every Sunday because that's how he keeps current and because he genuinely enjoys it.