A small amount of text data given to a web browser by a web server. The data is stored and returned to the specific web server each time the browser requests a page from that server. The main purpose of is to pass a unique identifier to the website so that the website can keep track of the user as they step through a website. For example, a protected site may store a temporary identifier in a/an after you successfully log in, indicating that you are an authorized user. The name derives from UNIX objects called magic . These are tokens that are attached to a user or program and change depending on the areas entered by the user or program. are also sometimes called persistent because they typically stay in the browser for long periods of time.