When a user visits the e-commerce site for the first time, the website will return a cookie number, which is stored on the user’s host, managed by the browser. The cookie number is present in cookie header and is generated by the server of the e-commerce website, and the number is unique for every customer. The client receives the response along with the header and the number with a line appended to a special cookie file. The file contains the server name and the user’s associated ID number.
In the subsequent request to the same server the client includes a cookie header which consists of a header line which specifies the id number for that server. During each visit or purchase from the e-commerce website, the browser sends the cookie number back to the website server. This cookie number is used to identify the user (or browser) who is visiting the site.