How you are tracked online
Computer Science · Key Stage 3 · The School
What a cookie actually is
A COOKIE is a small piece of text a website stores in your browser. It can remember that you are logged in, or what is in your shopping basket. Some cookies are set by the site you are visiting. Others, THIRD-PARTY cookies, are set by advertising companies whose code sits quietly on many different sites at once.
Building a profile from many small clues
A third-party cookie can see you visit a shoe website, then a travel site, then a news site — because its code sits on all three. Over time this builds a PROFILE: your interests, your habits, sometimes your location. No single click reveals much. Thousands of small clues, joined together, reveal a lot.
Why the adverts feel so accurate
Advertisers do not guess what you want. They buy access to a profile built from real tracked behaviour, then show an advert matched to it. That is why a search for one product can be followed by adverts for it on completely different sites for days afterwards. It is not a coincidence. It is the same tracked profile, followed from site to site.
A few real, simple habits cut down tracking without breaking the internet for you. Rejecting non-essential cookies on a consent banner, rather than accepting everything, blocks most third-party tracking on that visit. Browser settings can block third-party cookies by default. Private or "incognito" browsing does not hide you from the websites themselves — it only stops your OWN computer keeping a local history. None of this makes you invisible. Each step removes one more source of the small clues a profile is built from.