Glossary
Tracking pixel
A tracking pixel is a tiny invisible image or code snippet placed in a page or an email that loads from a third-party server, telling that third party you opened it and passing along details such as your network address, device and the page you were on. It works by being fetched, so it needs no click.
GlossaryPrivacyBillingSafety
Where you see it
You do not see it at all. You see its effects - an advertisement on an unrelated site that matches something you looked at, or a marketing email that registers as opened - and you see the companies behind it named in a privacy policy and in the manage panel of a cookie banner.
Why it matters
Pixels are how activity gets joined up across different sites, which is why refusing cookies on one site does not end the whole picture. The email version is the one most often forgotten: setting your mail client to stop loading remote images blocks it, and that is a separate control from anything in your browser.