What is Real-Time Bidding (RTB) — the auction that sells your data in 100ms

The invisible auction that happens every time you load a page

You open a webpage. Before the content even finishes loading, something extraordinary has already happened: your browsing profile has been packaged, broadcast to hundreds of potential advertisers, auctioned, and sold. An ad has been selected specifically for you. All in less time than it takes to blink.

This is Real-Time Bidding (RTB) — the technical mechanism that underlies most of the digital advertising industry. Understanding how it works is essential to understanding why your browsing data has value, and who benefits from it.

The anatomy of an RTB auction

When you visit a website with ad inventory, here's exactly what happens:

1. Page load trigger (0ms): Your browser begins loading the page. The publisher's ad server detects an available ad slot.
2. Bid request broadcast (10–20ms): The publisher sends a bid request to an ad exchange (Google Ad Manager, AppNexus, etc.). This request contains your profile: location, device type, browser, time of day, inferred interests, previous site visits, and a pseudonymous user ID linked to your behavioral history.
3. Demand-side platforms bid (20–80ms): Advertisers' DSPs (Demand-Side Platforms) receive the bid request, evaluate your profile against their targeting criteria, calculate a bid price, and respond. Hundreds of DSPs can bid simultaneously.
4. Auction resolution (80–100ms): The exchange selects the winning bid. Typically the highest bidder wins but pays the second-highest price (second-price auction).
5. Ad delivery (100ms+): The winning ad is delivered to your browser. The entire auction has concluded before most of the page's content has loaded.

What's in the bid request?

The bid request is the document that contains your data. The IAB's OpenRTB specification (the industry standard) defines hundreds of possible fields. A typical bid request might include:

• Your pseudonymous user ID (often linked to a long-term behavioral profile)
• Geographic coordinates or city/region
• Device type, operating system, browser version
• The URL of the page you're visiting
• Audience segments you've been placed in (e.g., "in-market for a car," "frequent traveler," "health-conscious consumer")
• Time of day and day of week
• Connection type (WiFi, mobile data)
• Previously visited sites (via cookie matching or identity resolution)

This information is shared with every DSP that receives the bid request — not just the winner. According to research by Dr. Johnny Ryan (Irish Council for Civil Liberties), a single page load can send this data to hundreds of companies. Across a typical day of browsing, your data may be broadcast to thousands of companies you've never heard of.

The data leak problem

RTB has a fundamental privacy problem that goes beyond what most people realize. Because bid requests are broadcast to all potential bidders — not just the winner — your data is shared with hundreds of companies for every single ad impression. These companies receive your data regardless of whether they win the auction. There is no technical mechanism preventing them from storing, analyzing, or further sharing this data.

The IAB's own data shows that RTB generates 8.4 trillion bid requests per day globally. Each one contains personal data. This represents arguably the largest data sharing operation in history — running continuously, in real time, across the entire web.

How Data Mirror detects RTB activity

RTB traffic is visible in network requests. Data Mirror monitors all outgoing network calls from your browser and identifies requests to known ad exchanges, DSPs, and bidding infrastructure. When it sees a call to DoubleClick (Google's ad exchange), AppNexus, Pubmatic, Rubicon, or other RTB platforms, it flags it, estimates the data value of that event, and adds it to your running total.

The "This visit" panel shows you the estimated value generated from the RTB activity detected on the current page. The 30-day earn bar aggregates this across all your browsing.