Sometimes when browsing a website, information relevant to that session can be useful if the user returns to the same website later on. Instead of going through processes such as authentication again, it can be quicker for both parties if the data in question can be stored and retrieved instead. A cookie is a file which stores information about the session on the user’s computer. When the user returns to the website later on, the cookie is sent to the server, which allows the server to identify the user from their earlier session.
Cookies are a big issue in privacy, since they can be used to identify users browsing habits across the web. If websites share information about their visitors and their associated cookies with each other, they are able to form a much more powerful understanding of their visitors, based on their browsing habits across other websites.
Last updated: 8 March 2018