2.1 From Click to Database

You click a link. It takes less than a second. In that moment, dozens of systems record the event, exchange information about you, and log the interaction in servers you will never see. This lesson traces that invisible journey.

The moment of the click

When you visit a webpage, your browser sends a request to the site's web server. The server responds with the page's HTML — but that document typically contains instructions to load resources from many other servers: fonts, images, analytics scripts, and advertising code. A single page visit can trigger requests to 30, 60, even 100 different domains (Englehardt & Narayanan, 2016, Princeton Web Transparency & Accountability Project).

Each of those requests tells the external server: your IP address, your browser type and version, the page you are visiting, the time, and any cookies that domain has previously set on your device. The external server already knows you — or can link you to a prior visit.

Third-party scripts: the infrastructure layer

Third-party scripts are small programs included in websites by the site owner, written and controlled by external companies. Common examples include:

• Analytics scripts (e.g. Google Analytics) — record which pages you visit, how long you stay, what you click
• Advertising pixels (e.g. Meta Pixel, Google Ads tags) — confirm that you visited a page, enabling retargeting
• Session recorders (e.g. Hotjar, FullStory) — capture mouse movements, scroll depth, even keystrokes on forms

The site owner pays for or benefits from these scripts. You may never know they are running.

Cookies: the memory mechanism

A cookie is a small text file placed on your device by a website. First-party cookies are set by the site you are visiting — they remember your login, shopping cart, or preferences. Third-party cookies are set by external scripts embedded in the page; their purpose is tracking across sites. If the same ad network has scripts on thousands of websites, it can observe your browsing across all of them.

From browser to database

The data collected — your click, the page URL, your device profile, a timestamp — flows to multiple destinations simultaneously. An analytics platform logs it for the site owner. An advertising exchange receives a bid request encoding your audience segments. A Content Delivery Network (CDN) logs the request for performance purposes. Your interaction becomes a row in a database, joined to prior rows, building a behavioural record over time.

Your takeaway

No web visit is a private exchange between you and one site. It is a many-party transaction in which your behaviour is observed, packaged, and passed along in milliseconds. Knowing this is the first step toward making more informed choices about the sites you visit and the tools you use.