DSP (demand-side platform)

A demand-side platform is software that buys advertising impressions on behalf of advertisers by receiving bid requests from exchanges and supply-side platforms, deciding whether and how much to bid in real time, and managing budgets, targeting, creatives and reporting across many sources of supply.

In OpenRTB terms the DSP is the "bidder": the party that receives a bid request and returns a bid response within the exchange's tmax (OpenRTB 2.6). The UK Competition and Markets Authority's market study describes DSPs as the intermediaries advertisers and agencies use to buy inventory across exchanges and SSPs, and found the intermediation chain opaque enough to merit intervention (CMA, Online platforms and digital advertising market study, July 2020).

A DSP's engineering problem is throughput: it must evaluate hundreds of thousands of requests a second, apply a bidding model, enforce pacing and frequency rules, and answer within tens of milliseconds. Its commercial problem is fees. The ANA's benchmarks, as reported by ExchangeWire, found that 43.9% of a dollar entering a DSP reached the consumer in 2024 and 45.1% in Q2 2026 (ExchangeWire, 16 September 2026). DSPs come as rented platforms, white-label platforms, "bidder as a service" and self-hosted stacks; the differences are set out in DSP vs SSP: the difference.

Example: a retailer's offsite program runs through a DSP seat that receives a bid request for a news site impression, matches the user to a loyalty-derived segment via a clean-room ID in user.eids, bids $4.20 CPM, and wins at the first-price clearing value.

Related: SSP, ad exchange, bid request, QPS, working media.

Source: IAB Tech Lab, OpenRTB 2.6 (bidder role); UK CMA market study final report (1 July 2020).

1. OpenRTB 2.6
2. CMA, Online platforms and digital advertising market study, July 2020
3. ExchangeWire, 16 September 2026