Win rate

Win rate is the share of a bidder's bids that win the auction, calculated as impressions won divided by bids submitted, usually for a campaign, deal, exchange or supply path.

Win rate is a buyer's metric. The UK CMA notes that DSPs judge sell-side partners on two rates. Bid rate is how often they want to compete for an impression, and win rate is how often they win it (CMA, Appendix M, paragraph 214, 1 July 2020). When several SSPs sell the same inventory, comparing win rates shows which paths clear best, and DSPs move spend toward them.

A low win rate can mean bids are too low, targeting is too narrow, or another buyer holds priority, for example through a preferred deal. A very high win rate can mean the bidder pays more than it needs to. OpenRTB helps the bidder tell these cases apart. An exchange can call the bid's loss notice URL, lurl, with a loss reason code, and it can report the minimum price that would have won (IAB Tech Lab, OpenRTB 2.6).

Publishers track a mirror metric for deals: how often a deal's buyer bids and wins when offered an impression. A preferred deal with a low win rate is a sign that the price or the targeting is wrong.

Example: A DSP sends 2,000,000 bids to one SSP in a week and wins 260,000 impressions, a 13% win rate. Through a second SSP selling the same publisher it wins 18% of its bids at a lower average price, so it shifts budget to the second path.

Related terms: bid-landscape data, bid shading, supply path optimization, loss notification, QPS.

Authoritative source: UK CMA, market study Appendix M, paragraph 214 (1 July 2020).