How the internet gets paid

You read the news for free. You watch cricket highlights, play a puzzle game on the bus and check the weather, and nobody asks for your card. Servers, journalists, game designers and video rights all cost real money, so somebody is paying. Most of the time that somebody is an advertiser, and the machinery that connects their money to your screen is called ad tech.

Think of a free local newspaper handed out at a train station in Mumbai or Tokyo. The paper costs money to print, but you get it free because shops pay to put their ads on its pages. The internet works the same way, except the "pages" are billions of screens, and the shops choose where to appear in a fraction of a second.

The three basic characters

Every ad story has the same three characters. A publisher owns something people pay attention to: a news site like Le Monde, a recipe blog, a mobile game, a streaming channel. An advertiser wants that attention: a car brand, a shoe shop, a bank launching a credit card in Brazil. And you, the audience, whose eyeballs are what is being bought and sold.

The publisher sets aside spaces for ads, called an ad slot. The total supply of those spaces over time is the publisher's ad inventory. Each time an ad actually loads in a slot and is shown to a person, that counts as one impression. The impression is the basic unit of the whole industry, the way a litre is the basic unit of milk.

What happens when a page loads

1. You open a pageYour browser or app asks the publisher's server for the article, and the page arrives with a few empty boxes reserved for ads.
2. The page asks for adsCode in each box calls an ad server, a system that decides which ad should fill that box right now.
3. A decision is madeThe ad server looks at deals the publisher has already signed and, often, runs a live auction among many buyers.
4. The ad appearsThe winning ad's image or video is delivered to your screen, and the impression is counted by both sides.
5. Money moves laterAt the end of the month the advertiser (or its agency) is invoiced for the impressions and the publisher is paid its share.

All of this happens before you finish reading the headline. When the choosing is done by software instead of a person negotiating on the phone, the industry calls it programmatic advertising. You will learn how that works in detail in the next track.

Two kinds of internet: gardens and the open web

Not all ad money flows the same way. Some companies own both the audience and the ad-selling machinery: Google Search and YouTube, Meta's Facebook and Instagram, Amazon, TikTok. These are called a walled garden because everything happens inside their walls. The advertiser buys through their tools, measures with their numbers, and never touches the wider market.

Everything outside the gardens is the open web: independent news sites, blogs, most apps, many streaming channels. Here, thousands of publishers and buyers meet through shared marketplaces run by many independent companies. The open web is where most of the "middle" companies you will meet in this track live, and it is also where most of the confusion, hidden fees and fraud happen, because so many hands touch each impression.

How big is this?

Advertising is one of the main business models of the entire internet. In the United States alone, the benchmark industry report from the Interactive Advertising Bureau and PwC counts close to three hundred billion dollars a year, and the number has grown almost every year since the mid-1990s.

Other large markets follow the same pattern. In India, mobile-first news and video apps survive mostly on ads because few people pay for subscriptions. In Japan and Brazil, big media groups mix subscriptions with advertising. Almost everywhere, ads are what keep the "free" in free internet.

Why ad tech exists at all

If there were only ten websites and ten advertisers, they could just email each other. Instead there are millions of sites and apps and millions of advertisers, in every language and currency. No human sales team can match them all. Ad tech is the set of tools that makes this giant matchmaking possible: deciding which ad goes where, counting what happened, checking it was real, and moving the money.

That usefulness comes with a cost. Each tool in the chain takes a fee, and each handoff is a place where things can be faked. Bots can pretend to be people, cheap sites can pretend to be famous ones, and money can quietly disappear between hops. Understanding the basic plumbing is the first step to seeing where that happens.