Guides
What is programmatic advertising? A plain-English explainer
Programmatic advertising is the automated buying and selling of digital ads, decided by software in an auction that runs in the time it takes a page to load, instead of by salespeople negotiating insertion orders. This is the short, honest version: who is involved, how one impression gets sold, and where the protocol underneath, OpenRTB, fits.
The core idea
Traditionally, a publisher's sales team sold ad space directly: a fixed number of impressions at a negotiated price, booked in advance. Programmatic replaces that manual step with automation. When a person opens a page or app, the ad slot is offered for sale and buyers compete for that single impression in real time. The whole transaction, offer, bids, winner, and served ad, happens in roughly the low tens of milliseconds, before the content finishes loading.
Who is involved
- Publishers and SSPs on the sell side, offering inventory.
- Advertisers and DSPs on the buy side, deciding what to bid.
- Ad exchanges in the middle, running the auction.
- Data and identity providers supplying the signals buyers reason over.
The full breakdown of the sell-side, buy-side, and marketplace roles is in SSP, DSP, and ad exchange.
How one impression gets sold
1. A person opens a page or app with an ad slot. 2. The publisher's SSP offers the impression to an exchange. 3. The exchange sends a bid request to many buyers at once. 4. Each buyer's DSP decides, in milliseconds, whether and how much to bid. 5. The exchange picks the highest eligible bid. 6. The winning ad is returned and rendered on the page.
Steps 3 through 5 are real-time bidding (RTB), the auction at the heart of programmatic. The messages in steps 3 and 4 are OpenRTB.
It is not all open auctions
"Programmatic" does not mean "open free-for-all." The same automated pipes carry several kinds of deal, from the fully open auction to committed, fixed-price buys that look like traditional direct sales executed through software:
- Open auction: any eligible buyer competes.
- Private marketplace (PMP): a closed auction among invited buyers.
- Preferred deal: a fixed price offered to one buyer with first look.
- Programmatic guaranteed: fixed price, fixed volume, committed.
How OpenRTB expresses each of these is covered in deals and PMP.
Where OpenRTB fits
None of this works without a shared language. If every exchange and every DSP spoke a different format, no buyer could bid across the market. OpenRTB is the IAB Tech Lab standard that lets thousands of exchanges and bidders interoperate: the common structure of the bid request an exchange sends and the bid response a buyer returns. It is the layer that makes "programmatic" a single market rather than a thousand incompatible ones. For the protocol itself, see what OpenRTB is.
Where validation fits
Because the whole market runs on those messages, a malformed bid request or response costs real money, in dropped bids and rejected inventory, without throwing an error anywhere. That is what a validator is for. Paste a bid request into the tester to see it checked against the spec, or start with how to validate a bid request.