Programmatic
Bid shading
Bid shading is a technique DSPs use in first-price auctions to lower a bid automatically toward the price actually needed to win, so advertisers do not overpay.
When exchanges switched to first-price auctions, buyers lost the automatic discount of second-price rules. If a DSP bid its full value, it would overpay every time. Bid shading is the fix: an algorithm predicts, for each impression, the lowest bid likely to win (using historical clearing prices, win rate data and the bid landscape) and "shades" the bid down toward it.
For example, if the advertiser values an impression at US$5 but similar impressions typically clear around US$3.20, the DSP might bid US$3.40. Some SSPs and exchanges also offer their own shading, and some share minimum-bid-to-win data after auctions to help buyers calibrate.
Bid shading is legitimate, but it matters who controls it and how transparent it is. Buyers should know whether their DSP is shading and how savings are shared; publishers watch whether aggressive shading erodes their revenue and respond with smarter floors.
Think of it like this
Bid shading is like offering a little under the asking price on a house because you know from recent sales what it will probably go for.
An example
A DSP's maximum is US$6 CPM; its model predicts a 90% chance of winning at US$4.10, so it bids US$4.10 and saves the advertiser US$1.90 per thousand.
Related terms
First-price auction
A first-price auction is an auction in which the highest bidder wins and pays exactly what they bid, which is now the standard model in programmatic advertising.
Second-price auction
A second-price auction is one in which the highest bidder wins but pays just above the second-highest bid (or the floor), which was the original standard in real-time bidding.
Win rate
Win rate is the percentage of bids a buyer submits that actually win the auction, calculated as auctions won divided by bids placed, multiplied by 100.
Bid landscape
A bid landscape is an estimate of how many impressions a buyer could win, and at what cost, at different bid prices for a given audience or inventory.
Auction dynamics
Auction dynamics are the rules and behaviours that decide who wins programmatic ad auctions and at what price, including auction type, floors, fees, bid shading and bid order.