Overview

When a client (e.g. a browser tab) makes HTTP requests to a server, the server does not know if the requests came from the same client. This makes it difficult to maintain state information (e.g. the users identity).

A solution which is transparent to the client involves the server sending a cookie to the client. Once the cookie is sent the client will automatically add the cookie to any subsequent request it makes to the server (assuming cookies are enabled). By checking the cookie the server can know which client has sent the request.