Tracking cookies are a specialized type of cookie that can be shared by more than one website or service. They are commonly used for legitimate marketing and advertising purposes, but because they contain a history of the user's actions on multiple sites, they may be exploited or misused to track the user's behavior.
Marketing and advertising
When used for marketing, a website may share its tracking cookie with a third-party analytics service, which examines how visitors behave so they can improve the site's designs or offerings.
It is also common for a third-party advertising service to offer advertising content and a tracking cookie that can be shared between sites, so that whenever a visitor moves from one site to another, they can be shown new advertising instead of the same content they had previously seen.
Advertising and marketing services typically anonymize and collate data from thousands or even millions of users, making it highly unlikely that any individual's habits are closely examined. Many users however still express discomfort at the idea of their web browsing habits being tracked.
Most modern web browsers allow users to block websites from saving cookies onto their computers, or only allowing certain websites to do so. Alternatively, many privacy-conscious users just clear their browser cache after every session to remove any saved cookies, or use security software to do so.
Many websites do not function correctly if cookie use is disabled. For example, websites with password-protected areas and retail sites with shopping cart systems usually require cookies for certain features to work.
Examples of tracking cookies include: