What is win rate?
Win rate is the share of a bidder's bids that win their auctions, calculated as wins divided by bids submitted. It is the main feedback signal for buy-side pricing: too low and the bidder wastes compute and misses delivery, too high and it is probably overpaying. Some reports divide wins by bid requests received instead, so check which denominator a number uses before comparing it.
Also called: bid win rate, auction win rate.
How it works
A bidder learns of a win when the exchange calls Bid.nurl, the win notice, and learns that the impression became billable when the exchange calls Bid.burl. These are different events, so a win rate built on win notices runs higher than one built on billing notices; the gap is the share of wins that never rendered or never met the exchange's billing rule. Loss notices sent to Bid.lurl carry a reason code in ${AUCTION_LOSS}, and code 0 means the bid won, so a bidder can count every outcome from one pipeline.
Win rate only means something next to price. Under first price, a bidder can raise its win rate by bidding more and paying more on every impression, so shading models trade the two off using the clearing price and the ${AUCTION_MIN_TO_WIN} value the exchange returns. Under second price, a higher bid raises the win rate without changing what the bidder pays on auctions it would have won anyway.
Low win rates often have a non-price cause worth ruling out first. Bids that reference an Imp.id the request never offered, use a currency outside BidRequest.cur, or come from a seat excluded by BidRequest.wseat are discarded before ranking, yet they still count as bids in the denominator. Loss reason codes 1 to 10 and the 200 range separate these filtered bids from bids that simply lost on price, which is code 102.
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Related terms
Every term is in the glossary.