Definition
Real-time bidding (RTB) is the mechanism by which most programmatic display, video and native inventory is bought and sold: each time a page loads an ad slot, an auction is held in the milliseconds before render, ad exchanges pass a bid request describing the impression (site, placement, user signals, format) to many potential buyers, and the highest bidder's ad is served. The whole exchange happens per impression, in real time.
RTB lets a buyer value each impression individually rather than buying a placement in bulk. A demand-side platform (DSP) receives the bid requests, applies the buyer's targeting and bidding logic, and responds with a price for the impressions worth buying.
This granularity is powerful but comes with the transparency and quality problems of the open programmatic supply chain: made-for-advertising sites, domain spoofing, and layers of intermediaries taking a cut.
In context
For iGaming, RTB/programmatic is used mainly in regulated markets where a licensed operator can run compliant display and video at scale through a DSP, applying brand-safety controls, allow-lists of vetted publishers, and third-party verification to avoid the worst of open inventory. It is less relevant to grey affiliate media buying, which concentrates on push, pop, native networks and paid social where entry is easier and inventory is cheaper.
Key concepts around RTB that a buyer should understand: the bid request and the signals it carries; first-price versus second-price auction dynamics (most exchanges moved to first-price, so bid shading and careful bid strategy matter); private marketplaces and programmatic guaranteed deals, which trade some of RTB's openness for vetted inventory and priority; and the supply-path optimisation problem of choosing the shortest, cleanest route to an impression to reduce fees and fraud. For an operator, a well-run programmatic setup with strict allow-lists and verification can be an efficient Tier-1 acquisition and retargeting channel; a lazy one funds ad fraud.
Worked example
A licensed operator runs programmatic display and video through a DSP in three regulated markets, with an allow-list of 400 vetted publishers, third-party viewability and fraud verification, and supply-path optimisation to the cleanest exchanges. It uses this for prospecting and retargeting at a cost per FTD competitive with paid social, and audits the supply path quarterly.
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