How to prevent a user from having multiple instances of the Same Web application

Question

I\'m wondering if it is possible to determine if a user already has a web browser open to the web application I\'m working on. It seems that they can open several instances

Answer 1

You can stop the page functionality when user opened another tab or another window or even another browser

  $(window).blur(function(){

// code to stop functioning or close the page  

});