A Cookie („cookie“) is usually a small text file containing information that can be set by a website. Exactly this site can also read the cookie again. Cookies are defined in RFC 2965.
One can roughly distinguish two types of cookies:
- Session Cookies
- Persistent Cookies
Session Cookies
Session Cookies exist only in memory and are lost when the browser is closed. In particular, they are not written to disk, and are therefore no longer available at a later session. The main task is storing login and authorization data, and similar information that is needed only in one session.
Persistent Cookies
Persistent Cookies, however, are stored to be available in later sessions. They are usually equipped with a lifetime, after that the browser shall remove them. The main task is the storage of login data across sessions, as well as the filing of personalization information by the user on the machine of the user. Examples include selected colors, layout, fonts, etc.
Cookies are not critical in principle. However, large provider with access to a huge number of sites can use cookies to get an overview of the pages visited by a user. An example here are ad networks that can set and read their cookies on all sites that use the ads.
More restrictive cookie settings prohibit this. In addition, you can clear cookies, or disable cookies, which could lead to problems on some pages.
