What is clearing price?
The clearing price is what the winning bidder actually pays for an impression. In a first-price auction it equals the winning bid; in a second-price auction it is set just above the runner-up, or at the floor. The exchange reports it to the winner by substituting the ${AUCTION_PRICE} macro in the win or billing notice, in the bid's currency and CPM units.
Also called: auction clearing price, winning price, AUCTION_PRICE.
How it works
Bidders place ${AUCTION_PRICE} in Bid.nurl, Bid.burl, or the markup, and the exchange replaces it with the price before calling the URL or serving the ad. Since 2.6-202606 the spec defines that value as the price after any seller discount, with ${AUCTION_DISCOUNT_PCT} and ${AUCTION_DISCOUNT_CPM} describing the discount. ${AUCTION_MBR} reports a ratio instead, clearing price divided by bid price, which lets an exchange share proportions without exposing absolute prices.
Exchanges often encrypt the price when it travels through the browser, using a scheme agreed with the bidder and marked by a suffix on the macro name, such as :B64. An exchange may also replace the macro with an empty string when its policy forbids disclosure. Bidders must handle both cases and should never assume the expanded value is a plain number.
The exchange's clearing price is not always the final word. When Source.fd is 1, an upstream ad server or wrapper makes the last decision, so a bid that wins the exchange auction can still lose there. Count spend from billing notices rather than win notices, and log the price with ${AUCTION_CURRENCY} and the auction ID, or reconciliation across currencies breaks.
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Related terms
Every term is in the glossary.