Cookies are small files that are stored on a computer. Cookies are designed to store a modest amount of data that is specific to a particular client and website. Cookies can be accessed through either the computer or the web server. This enables the server to supply a page tailored to a particular user. The page itself can also contain some script which is alert of the data in the cookie and thus is so able to carry information from one website to the next.

Each cookie must be read by the code on the web server or the computer so that the data can be reached and used to modify the web page applicably. Each cookie also has its own lookup table that contains pairs of values. The lookup table is usually rather small.

Cookies are created when a new web page is loaded. Writing data to a cookie is usually done after a ‘submit’ button is pressed.