AdTech

Anyone who opens a news site will almost always see advertising there. This advertising is not chosen by a human, but by software. AdTech is the umbrella term for exactly this software: programs that sell ad space, match ads to users, and measure delivery. The name comes from English and is the short form of “Advertising Technology”. Between the click on a link and the fully loaded screen lies an automatic trade that the reader does not notice at all. It typically takes less than a tenth of a second.

Why so much money is tied to ad space

Advertising finances a large part of the free internet. News sites, video platforms, and free apps earn most of their money through ads. Worldwide, several hundred billion euros are generated through this every year. AdTech is the machinery that distributes this money.

For the big tech companies, this is the central source of revenue. At Alphabet, the parent company of Google, the vast majority of revenue comes from advertising. Meta, too, with Instagram and Facebook, lives almost exclusively off it. When business news mentions weak advertising revenue, it is usually about exactly these systems.

At the same time, the industry is under political pressure. To select suitable ads, the systems collect data on user behavior. Data protection authorities in Europe therefore regularly examine whether this collection is even permitted. This makes AdTech a topic that occupies not only engineers, but also lawyers and politicians.

The auction that starts when a page loads

The core of the system is a real-time auction, known in technical jargon as Real-Time Bidding. As soon as a page loads, the ad slot signals: there is space available here. This signal goes to an intermediary platform that bundles many ad slots together. From there, it is passed on to interested advertisers.

Advertisers are provided with a bit of information along with the signal: approximate location, device type, page visited, sometimes interests derived from earlier browsing behavior. Based on this, their software automatically submits a bid. The highest bidder gets to show their ad and usually pays just a few cents for it. The entire process ends before the page has finished loading.

You can picture this like stock market trading, except instead of shares, individual eye contacts are traded. The comparison has a limit, though: on the stock exchange, the price is public, but in the ad auction it is not. How much of an advertising euro actually reaches the site operator is often hard to trace. Studies estimate that a significant share gets stuck along the way with intermediaries.

Spotting AdTech in your own browser

The system becomes most noticeable when a product follows you around. Anyone who has once searched for sneakers will see them again on other sites for days. This technique is called retargeting and is a classic AdTech tool. The cookie banners that appear when a page loads also belong to this category: they ask for permission to use data for the ad auction.

In business news, the term usually comes up in disputes or acquisitions. One example is the EU Commission’s antitrust proceedings against Google, which concerned its dual role as seller and auctioneer. Another is Apple's decision to allow tracking across apps only with explicit consent. According to Meta’s own statements, this change cost the company around ten billion dollars in revenue in a single year.

A common misconception is that AdTech is the same as the phone supposedly listening in on conversations. There is no evidence for this, and the systems don’t need it either. Search history, location, and pages visited are enough for astonishingly accurate predictions. Newer systems increasingly rely on machine learning for this, meaning programs that derive patterns from large amounts of data.