Pixel
A tracking pixel is a tiny, usually invisible image or script request loaded from a third-party server that reports the page view, the visitor's identifiers and events such as purchases to that third party.The original pixel was a 1 by 1 transparent image whose URL carried parameters: the page, a campaign identifier, the time. When the browser fetched it, the server logged the request, read its cookies and could set new ones. Modern pixels are JavaScript snippets (the Meta Pixel, the LinkedIn Insight Tag, the TikTok Pixel, Pinterest and Snap tags) that collect far more: button clicks, form fields, product views, purchase values and hashed emails for matching, and they set or read third-party cookies on the advertiser's domain. Email pixels do the same inside newsletters to report opens.
Pixels are squarely within the EU cookie rules. The EDPB's Guidelines 2/2023 on the technical scope of Article 5(3) of the ePrivacy Directive name tracking pixels and URL tracking among the techniques that constitute gaining access to information stored on the device, so prior consent is required unless the pixel is strictly necessary, which an advertising pixel never is. Under the CCPA, sending visitor data to an advertising platform through a pixel is sharing for cross-context behavioral advertising, which triggers the opt-out right; the Healthline settlement of 2025 ($1.55 million) concerned exactly that.
A consent tool handles pixels by not loading them until the marketing category is accepted, whether they sit in the HTML or are injected by a tag manager, and by passing the consent state to Google Consent Mode for Google's own tags. See the Meta Pixel setup.