How to Always Start Google Chrome in Private Browsing Mode
У вашего броузера проблема в совместимости с HTML5
To activate Google Chrome’s Incognito(Private browsing) mode by default, you must add a command line option to its shortcut.
For doing it in all the browsers visit: http://www.rybersoft.com/2017/06/how-to-set-private-browsing-as-default.html