Programmatic · also called auction duplication, duplicate bid requests
Bid duplication
Bid duplication happens when the same ad impression reaches a buyer through several SSPs or resellers at once, so the buyer may bid against itself and waste processing and budget.
With header bidding, a publisher sends each impression to many SSPs simultaneously, and resellers may pass it on further. A single DSP can therefore receive five, ten or more bid requests for the same impression, each looking slightly different.
This causes several problems. The DSP may bid through several paths and effectively compete against itself, pushing up the price. Infrastructure costs soar for everyone. Reports inflate the apparent size of available supply. And because every path claims to sell the same premium inventory, it is harder to spot fake paths hiding among real ones, which domain spoofing exploits.
The main remedy is supply path optimization: DSPs identify duplicates (for example through transaction IDs defined in OpenRTB and Prebid) and bid through only the best path. Sell-side demand path optimization and pruning reseller lines in ads.txt help too.
Think of it like this
Bid duplication is like the same house being listed by six estate agents, so one buyer ends up making several offers against themselves.
An example
A DSP receives 7 bid requests carrying the same transaction ID from one news page view; its SPO logic bids only through the direct SSP path.
Related terms
Supply path optimization (SPO)
Supply path optimization (SPO) is a buyer's practice of choosing the most direct, cheapest and most trustworthy routes to the same inventory, and cutting unnecessary resellers and duplicate paths.
Header bidding
Header bidding is a technique where a publisher offers each ad impression to many SSPs and exchanges simultaneously before calling its ad server, so all buyers compete at once.
Bid request
A bid request is the message an SSP or exchange sends to potential buyers describing an available ad impression, inviting them to bid on it in a real-time auction.
Reseller
A reseller is a company authorised to sell a publisher's ad inventory through an ad system account that it controls, rather than the publisher's own account, and labelled RESELLER in ads.txt.
Demand path optimization
Demand path optimization (DPO) is a publisher's or SSP's practice of prioritising the buyers and routes that deliver the most value, and cutting those that add cost without adding demand.