RTB (real-time bidding)

RTB (real-time bidding) is an automated auction in which buyers bid for an ad opportunity just before it plays, and the highest bid wins. It is one of the ways programmatic advertising is bought.

How does it work?

On the web, the auction runs for each page view. On digital out-of-home (DOOH) screens, in streets, malls and stations, it runs for upcoming plays, or short blocks of plays, in a screen’s loop. The steps are the same:

• Announce. The screen owner’s platform, the SSP, describes an opportunity: which screen, where, when, and the estimated audience.
• Evaluate. Buyers’ platforms, the DSPs, check it against their campaigns’ rules and budgets.
• Bid. Each interested DSP sends a price, usually as a CPM.
• Pick. The SSP compares the bids with the floor price and selects the winner.
• Play. The winning creative is scheduled on the screen.

Because a single play on a public screen can reach several people at once, the price of one play is derived from the CPM and the audience estimate for that play. The same bid can buy a very expensive play or a very cheap one.

Example

Illustrative example: a screen outside a station has a slot coming up at 8:00 on a Monday, with an estimated 40 people in front of it. Two DSPs bid CPMs of €10 and €15, and the floor is €6. The bid at €15 wins. For 40 estimated viewers, that play costs €0.60. At 23:00, with 4 people estimated, the same CPM would put the play at €0.06.

Why it matters when you plan a DOOH campaign

RTB gives you flexibility: you pay the market price, only for plays that match your rules, and you can change course during the campaign. The flip side is that nothing is guaranteed. If another buyer bids more on your key screens at your key hours, your ad simply does not play there.

Yet people remember what they see again and again in the same spot, and an auction cannot promise that. For that core presence, guaranteed deals or direct buying are safer. Auctions work well on top, to add reach where timing is flexible.