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RTB and programmatic media buying: a guide for advertisers
RTB (real-time bidding) is an auction mechanism in which every single ad impression is sold in real time, within tens of milliseconds as a page loads. Programmatic is the broader term: automated media buying through technological infrastructure, both auction-based and guaranteed. For an advertiser it means precision and scale, but without oversight it also means fees nobody mentions.
Daniel Votruba · 6 July 2026 · 4 min read
How the ecosystem works
On the advertiser side sits the DSP (demand-side platform), the tool that sets targeting, budgets and bids. On the publisher side the SSP (supply-side platform), which offers their inventory into the auction. Between them the ad exchange, the marketplace where supply meets demand. Buying comes in three modes: open auction (public auction, maximum reach, minimum control), PMP deals (private marketplace, an invitation auction of selected publishers on agreed terms) and programmatic guaranteed (fixed volume at a fixed price, merely executed programmatically). The more premium the brand and the more sensitive the context, the more it pays to move buying from open auction toward deals.
Why it all came about: classic direct buy meant ordering a bundle of impressions from one publisher and hoping your audience was hidden inside it. Programmatic inverts the logic. You are not buying a medium, you are buying a specific impression in front of a specific audience, wherever that audience happens to be. Hence the precision and the scale, and hence also the complexity of a chain that has to be actively managed.
DOOH: programmatic stepped off the computer screen
Digital outdoor surfaces, meaning screens in shopping centres, at stops, in airports and on facades, are increasingly bought programmatically. You are not buying a panel for a month but slots by time, weather, rush hour or the estimated composition of the audience nearby, and the creative can change dynamically. DOOH thus combines the credibility and unmissability of outdoor with the flexibility of online buying. An honest note: measurement remains estimated (impression multipliers, mobile data), so comparing DOOH with display one-to-one on CPM is a methodological error.
Brand safety and viewability: what to watch
The auction itself does not distinguish quality. Without safeguards a brand appears next to disinformation or on MFA sites (made for advertising), pages built purely to harvest programmatic budgets; a 2023 ANA study showed a worrying share of open web spend flowing to them. Basic hygiene: inclusion lists (buying explicitly permitted domains by name, not merely blocking banned ones), third-party verification tools (IAS, DoubleVerify, Adloox) and consistent tracking of viewability. The MRC standard counts a display impression as viewable when at least half the area is on screen for at least a second, which is a threshold, not an ambition. Paying for impressions nobody could have seen is the quietest form of waste in all of marketing.
The ad-tech tax: how much money actually reaches media
Between your invoice and the publisher stands a chain of intermediaries: DSP, SSP, data suppliers, verification, agency. And each takes a slice. An ISBA/PwC study (2020) on real campaign data found that on average roughly half the investment reached publishers and 15% of costs could not be traced at all (the unknown delta). Transparency has improved since then, but the principle holds: if you do not know how much you are paying to whom, you are probably paying too much. Contractually require a fee breakdown and access to log-level data; a serious supplier has no problem with that.
When to leave programmatic alone
Programmatic is not a universal answer. It makes no sense on very small budgets, where fixed setup costs swallow the effect; with extremely narrow B2B audiences, where the addressable group is smaller than statistical noise; and where a premium direct buy will secure a better position, format and context for comparable money. And a checklist of questions for your supplier: What is the complete fee breakdown? Do I get log-level data? Whose seat is it in the DSP, mine or yours? Who verifies brand safety and viewability? Are we buying through inclusion lists? How are PMP deals reported against open auction? Anyone who dodges the first question will dodge the invoice too.
Want programmatic with open cards, meaning your own seat, log-level data and no black box? This is how we buy media, or write to us directly. The first opinion is free.
Key takeaways (TL;DR)
- Programmatic does not buy a medium but a specific impression in front of a specific audience; the more premium the brand, the more it pays to move from open auction toward PMP deals and programmatic guaranteed.
- The auction does not distinguish quality: without inclusion lists, third-party verification and viewability checks, budgets flow to MFA sites and impressions nobody could have seen.
- The ad-tech tax is real: according to ISBA/PwC, on average roughly half the investment reached publishers and 15% could not be traced at all. Require a fee breakdown and log-level data.
- Programmatic is not universal: on small budgets, extremely narrow B2B audiences and premium contexts, direct buy can secure more for comparable money.
FAQ
What is the difference between an open auction and a PMP deal?
An open auction is public: the widest reach, the least control over inventory quality. A PMP is an invitation auction of selected publishers on agreed terms: higher price, guaranteed context. Programmatic guaranteed goes further still, a fixed volume at a fixed price, merely executed through programmatic infrastructure.
What is the ad-tech tax and how much of the budget actually reaches media?
The sum of fees charged by technological intermediaries between advertiser and publisher. An ISBA/PwC study (2020) found roughly half the investment reached publishers on average and 15% of costs could not be traced. A transparent setup with log-level data is therefore a condition, not a bonus.
What is programmatic DOOH?
Buying digital outdoor surfaces through programmatic infrastructure: targeting by time, weather or nearby audience, with dynamic creative. Outdoor gains the flexibility of online campaigns, albeit with estimated rather than individual measurement.
Sources: ISBA & PwC, Programmatic Supply Chain Transparency Study (2020) · ANA, Programmatic Media Supply Chain Transparency Study (2023) · Media Rating Council, viewability standards · our own practice across 750+ projects.