- A cookie (more formally known as an HTTP cookie) is a small piece of data that a server sends to a user's web browser. - The browser may store it and send it back with the next request to the same server. - Cookies are used to remember stateful information (such as items added in the shopping cart in an online store) or to record the user's browsing activity (including clicking particular buttons, logging in, or recording which pages were visited in the past).