What a DSP is, and whether you need one

A demand-side platform sits on the buyer's side of an automated marketplace. When an impression becomes available — a page loading, a stream starting — the platform decides in roughly a hundred milliseconds whether to bid on it and how much, based on the audience, the placement and the rules you set. Multiply that by billions of decisions and you have programmatic buying.

The value proposition is aggregation. Rather than negotiating with fifty publishers, you set an audience and a budget once and the platform sources inventory across all of them. That is genuinely useful, and it is why programmatic took the share of digital advertising that it did.

What it is not is a source of inventory. A DSP owns nothing. It buys from supply-side platforms and exchanges, which is the fact that explains the fee structure underneath it.

The platform fee is the number a DSP will quote you, and the range is wide. The Trade Desk's take rate was about 20.3% in 2024 on published analysis, with one to two points negotiable at $500,000 to $750,000 spend thresholds. DV360 sits around 10% to 15%. The generic tier runs 5% to 15%. All of those are desk research dated 3 August 2026, and take rates move.

Underneath that sit the fees nobody quotes. The supply-side platform takes roughly 10% to 15%, and an exchange layer a further 5% to 10%. Research on the cumulative supply chain has found publishers receiving as little as 40 to 50 pence of each advertiser pound once every intermediary has taken a share.

This is why the single most useful question to ask any buying platform is not its rate but its working-media percentage: how much of what you hand over actually buys advertising. A platform that cannot answer that is telling you something.

A DSP interface is built for a trader. It assumes somebody who understands bid strategies, inventory quality, supply paths and pacing, and who will look at it daily. That person is the actual cost of a DSP seat, and they cost considerably more than the platform fee at most volumes.

The common failure is a seat bought on the promise of control and then operated by somebody with four other jobs. An unattended DSP does not fail loudly; it quietly buys cheap inventory against a broad audience and reports impressions, which looks like activity and is not.

If you have that person, or an agency providing them, a DSP is likely the right tool and this guide is not arguing otherwise. If you do not, the honest options are a managed service, a lighter layer, or buying directly from the two or three sellers that matter to you.

Cinema and addressable television do not transact programmatically in the UK. Cinema is sold quote-based through two sales houses as packages against films whose performance is unknown until they open; addressable television is booked as paperwork against household attributes. Neither has a self-serve API, and no DSP covers them.

This matters if your plan is genuinely multi-channel, because it means a DSP is a partial answer by construction — you will be running the awkward half of the plan somewhere else regardless.

It is also worth knowing when reading a proposal. A platform describing cinema or UK addressable television as programmatic inventory is either mistaken or reselling somebody else's paperwork with a margin on top.