How they track you (I): what Google Analytics and the Meta Pixel really collect

Mechanism profile

Google Analytics 4 (GA4) and the Meta Pixel are two tracking tags that a website’s owner embeds in its pages so that every visit or action sends a message to Google’s or Meta’s servers.

• GA4 records, by default, the first visit, session start, language, location, page title, referring page, screen resolution, and two identifiers (client and session); then, through “enhanced measurement,” it also tracks page views, scrolling, outbound clicks, downloads, internal search, embedded video playback, and form start/submission. It distinguishes visitors with two cookies, _ga and _ga_<id>, which expire by default after 2 years.
• Meta Pixel collects what typically travels in HTTP headers (IP address, browser, page, referrer), the Pixel’s identifier, Facebook cookies, clicked buttons, and form field names. The values of those fields (email, phone…) are only captured if the website enables them through Advanced Matching, and they travel “hashed” with SHA-256 — a one-way conversion that nonetheless still allows the same person to be recognised.

Relationship with the «Vínculu dixital» hub

First piece in a four-part series on commercial digital surveillance. Same editorial hub as PISA 2025 and AI: knowing how much or for what isn’t enough: both pieces argue, from different cases (tracking surveillance / critical use of AI in the classroom), for a healthy digital bond grounded in data and evidence, not adjectives.