Details about the cookie system

Previous page - An introduction to cookies

Some sites store a lot of information about you within the cookie itself, but most use it only as an identifier. Usually the big file containing your data is at the site server end, and all the cookie does is make sure the correct data file is used.

Everything you do on the site can be logged in that data file - the pages you visit, how long you stay on them, which preceding page you arrived from, which adverts you click through, and what you buy. If you use the site a lot, the file will finish up bigger than your medical records. (See - What every site can find out about you.)

The content of the data file is used to adjust what you see on screen. For example, if you're in a book site and you spend most of your time in the cookery section, you'll find that the adverts you see - even in other parts of the site - will relate to cookery books. You'll get cookery book special offers on the front page, and maybe even some of the links will change so it's easier for you to find specialist cookery sections.

Unless you give the site your personal details, the data file remains anonymous. It contains your surfing habits, but doesn't know who you are as an individual.

This changes the moment you give the site any personal details. If you enter your email address, maybe to sign up for a newsletter, or give your credit card details to buy something, the data file is now tied to you as a person, and may include your name or at least your email address.

If you register for a site and have a username (often just your email address) and a password, your data file is matched to your username. Sometimes this is used alongside a cookie system and sometimes it's used as a replacement for cookies.

Most shopping sites ask you to register before you can buy anything. This is partly a security measure and partly a marketing ploy. When you come back, the site may automatically come up with your username and ask you to sign in. That means it's recognised you through its cookie system.

Introduction to cookies

Inspect

Control

Disallow

Delete