The Private Window won't keep history, sessions, and cookies. To be able to use No Trace, a user needs to install an add-on that blocks various requests like: browsing behavior, cookie manipulation, HTTP requests, address, IP, etc, defined within the browser. It's all related to browsing behavior. Additionally, you need to configure the browser to inform the servers to remove trace from their requests. Install the No Trace add-on then you will have the possibility to block these queries.