Cookies and web trackers: the basics
Session cookies, third-party cookies, trackers: how a site remembers you and follows you around the web, explained plainly.
What is a cookie?
A small text file a site stores in your browser, automatically sent back with every request to that same site — lets it remember a state (logged in, cart, preferences) between pages, since HTTP itself is stateless.
First-party vs. third-party cookies
| Type | Set by | Typical use |
|---|---|---|
| First-party | The site you're visiting itself | Session, login, preferences |
| Third-party | A different domain, embedded in the page (ads, social network) | Ad tracking across multiple sites |
Third-party cookies are increasingly blocked by default in modern browsers (Safari, Firefox) — Chrome is gradually following, pushing the ad industry toward other tracking techniques.
Beyond cookies: other tracking techniques
| Technique | Principle |
|---|---|
| Fingerprinting | Identifying a device through the unique combination of its traits (screen, fonts, browser…) |
| Local Storage | Browser-side storage, similar to cookies but not automatically sent to the server |
| Tracking pixel | An invisible 1×1 pixel image that signals a page load to a third party |
Consent banners
In Europe, the GDPR and the ePrivacy directive require explicit consent before setting non-essential cookies — hence the near-universal "Accept/Reject" banners, whose actual compliance varies a lot from one site to another.
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