Demystifying Digital Media: Demand Side Platforms

A demand-side platform exists to solve one problem: buying inventory across dozens of exchanges and SSPs shouldn’t require dozens of separate relationships and interfaces. What’s changed recently is how directly some DSPs are trying to bypass the supply side altogether, and what that’s actually cost them.

A demand-side platform is the buy-side counterpart to an SSP: one interface an advertiser or agency uses to bid on inventory across many exchanges and supply sources simultaneously, rather than negotiating and managing separate relationships with each one directly. The core function hasn’t changed much since the category matured. What’s changed is how some DSPs are trying to route around the supply side entirely.

What a DSP actually does

In practical terms, a DSP receives a bid request, evaluates it against the advertiser’s targeting criteria and budget in real time, submits a bid, and manages the resulting campaign reporting, all within milliseconds, at the scale of billions of auctions a day. The value proposition is aggregation: one login, one reporting dashboard, one set of targeting tools, standing between an advertiser and a fragmented landscape of exchanges that would otherwise each require separate management.

Most advertisers never interact with a DSP directly, an agency or trading desk typically operates it on their behalf, which is worth knowing when evaluating a media partner’s stack. Asking which DSP an agency actually runs campaigns through, and why that platform specifically was chosen over the alternatives, is a reasonable and underused question, since DSP choice genuinely affects available inventory, targeting capability and reporting transparency in ways that aren’t always visible from the campaign brief alone.

The standard path, and the shortcut some DSPs are building

The traditional path runs DSP to SSP to publisher, with the SSP handling curation, supply path optimisation and, often, brand safety screening on the way. Some DSPs have built direct publisher connections that skip the SSP layer, on the promise of lower costs and cleaner reporting once the intermediary’s fee and opacity are removed. The Trade Desk’s OpenPath is the highest-profile example, growing to reportedly around 10% of the company’s revenue by Q3 FY2025, with major CTV publishers connected directly.

What the shortcut has actually cost, in one case

In February 2026, Adweek reported that both Dentsu and WPP had quietly exited OpenPath, citing a lack of transparency into where spend actually landed and undisclosed fees, the same complaint direct connections were supposed to eliminate by removing the SSP. The full breakdown of what that means for how supply paths should be evaluated is covered in Disputing the “Dumb Pipes” Theory. The relevant takeaway for choosing a DSP specifically: a platform’s direct-connection product deserves the same scrutiny as any SSP relationship, not an assumption of automatic transparency just because an intermediary was removed from the chain.

What actually differentiates one DSP from another

Beyond the basic auction mechanics, which are largely standardised across the category, the real differentiators are supply path transparency (how clearly the platform discloses fee structures and where spend actually lands), targeting and measurement capability (first-party data integration, identity resolution options, incrementality testing tools), and inventory access quality (curated deal availability, brand safety screening depth, and genuine reach across CTV, display, audio and other formats rather than concentration in one). Auction speed and basic bidding logic are largely commoditised at this point. Transparency and measurement quality are where the real differences still live.