How ad tracking actually follows you — and where to cut it

Four layers, four cuts. (1) On the site: pixels and SDKs from ad platforms watch what you view and buy, tied to cookies or your login. Cut: reject non-essential cookies (see the banner rules), and browsers/extensions that block third-party trackers. (2) The identity graph: your email and phone number, hashed, stitch your behaviour across devices — this is how a shop purchase follows you into an app. Cut: alias emails per service, and the “off-platform activity” dashboards big platforms must offer — review and disconnect. (3) The auction: real-time bidding broadcasts your profile (site, location, interests) to hundreds of bidders in milliseconds — the part regulators keep hammering (the IAB consent-framework rulings, DPA fines on ad-tech intermediaries). You control little here directly — which is why layers 1–2 matter. (4) Data brokers: enrichment firms merge offline and online traces and sell segments. Cut: access and erasure requests work on brokers too — see Who has my data?. The honest summary: you cannot opt out of the ecosystem once, but the four cuts above remove most of the tail — and every DSA ad-repository and consent ruling shrinks the industry’s room further. Current fights: What’s changing.