Cookies, Tracking and Metadata
How websites recognize you again and what hidden information is stored inside photos and documents, explained in general terms.
Last updated: September 23, 2026
Cookies
What is a cookie
A small text file a website stores in your browser. On your next visit, the browser sends it back automatically, letting the website recognize you again without needing to log in again.
Session cookie
Gets deleted as soon as you close the browser. Typical for keeping you logged in during one visit.
Persistent cookie
Stays stored for days, months, or years, with a fixed expiration date. Often used for advertising purposes.
First party cookie
Set by the website you're actually visiting, for example to remember a shopping cart in an online store.
Third party cookie
Set by a third party, usually an ad network that's embedded on many different websites. This makes it possible to track your browsing across sites.
Cookie banner
The notice required by law to ask for consent before setting non essential cookies. "Reject all" is always legally allowed, even when some banners make it deliberately harder to find.
Tracking without cookies
A device can often be recognized again even without any cookies at all.
Tracking pixel
An invisible, one pixel sized image that confirms a page or email was opened when it loads, often together with the time and IP address.
Browser fingerprinting
Combines inconspicuous details like screen resolution, installed fonts and browser version into a kind of fingerprint that uniquely identifies a device even without cookies.
Local storage
A storage option in the browser similar to a cookie, but with more space and usable for longer, also sometimes used for tracking.
Metadata
Data about data, usually delivered invisibly alongside a file.
What is metadata
Extra information a file carries about itself, without it being visible in the actual content.
EXIF data in photos
Often includes the camera model, the time the photo was taken, and, if the smartphone had GPS enabled, the exact location coordinates of the shot.
Metadata in documents
Word and PDF files often store the author's name, editing timestamps, and sometimes even deleted text or comments from earlier versions.
Protecting yourself before sharing
Many operating systems offer a way to strip metadata before sending a file, for photos often called "remove location". Taking a screenshot of the content instead of sharing the original file also removes most metadata.
What happens to the collected data
Cookies, tracking and metadata together paint a picture of you that has value elsewhere.
Data brokers
Companies that specialize in combining data from many individual sources and reselling it as a ready made profile, usually without the affected person ever finding out.
What the data is used for
Mainly for personalized advertising, but also for credit checks, insurance rates, or political campaign ads targeted precisely at specific interest groups.
Is it legal
In the EU, the GDPR requires that personal data may only be processed with a legal basis, usually consent or legitimate interest. Trading data is generally allowed if these conditions are met, which in practice is often disputed and regularly ends up in court.
Your own rights
Under the GDPR, you have the right to ask any company what data it holds about you (right of access), and to request deletion (right to be forgotten).