JSESSIONID is a cookie generated by Servlet containers and used for session management in J2EE web applications for HTTP protocol. If a Web server is using a cookie for session management, it creates and sends JSESSIONID cookie to the client and then the client sends it back to the server in subsequent HTTP requests. JSESSIONID is a platform session cookie and is used by sites with JavaServer Pages (JSP). The cookie is used to maintain an anonymous user session by the server.