RTB in Action: From Page Load to Ad Display
Real-Time Bidding (RTB) happens in the blink of an eye — typically within 100 milliseconds of a user loading a webpage. Here is a step-by-step breakdown of exactly what happens during an RTB auction.
Step 1: User Visits a Website
A user navigates to a publisher's website. The page begins to load and the publisher's ad server detects that an ad slot is available (for example, a banner placement or a popunder).
Step 2: Bid Request is Sent
The publisher's Supply-Side Platform (SSP) or ad exchange — such as TwinRed — sends a bid request to connected Demand-Side Platforms (DSPs) and advertisers. This request includes:
- Ad slot specifications (size, format, position)
- Publisher domain and page URL
- User signals (device type, browser, operating system, geographic location)
- A unique auction ID and timestamp
Step 3: Advertisers Evaluate and Bid
Each DSP evaluates the bid request against its advertisers' campaign criteria. If the impression matches a campaign's targeting parameters (e.g., the user is in the right country, using the right device, visiting the right type of content), the DSP submits a bid response with:
- The CPM (cost per thousand impressions) price the advertiser is willing to pay
- The creative (ad) to display if they win
Step 4: The Auction Runs
The ad exchange collects all bid responses and runs the auction. In a standard first-price auction, the highest bid wins. In a second-price auction, the winner pays the second-highest bid price plus a small increment.
Step 5: The Winning Ad is Served
The winning advertiser's creative is returned to the user's browser and displayed in the ad slot — all before the page has finished loading. The entire process takes approximately 50–100 milliseconds.
Step 6: Reporting and Optimisation
After the impression is served, data is recorded: whether the ad was seen, clicked, or led to a conversion. Advertisers and DSPs use this data to refine their targeting and bidding strategies over time.
A Practical Example
Imagine a user in Germany opens a gaming website on their Android smartphone at 9pm. TwinRed's exchange detects an available ad slot and sends a bid request. An advertiser targeting male gamers in Germany on mobile devices bids €2.50 CPM. Another advertiser targeting all European mobile traffic bids €1.80 CPM. The first advertiser wins at €2.50 CPM, and their banner ad is displayed to the user — all in under 100 milliseconds.