I just wanted to ask what your preference is regarding if a person should be able to be logged in to an application from multiple devices / computers / browsers. In my authentication system, I’ve been more or less enforcing this through $_SERVER[‘HTTP_USER_AGENT’]. If a user is logged in from computer1, and then logs in from mobile_device1, computer1 will no longer be able to continue without signing back in. I know codeigniter by default drops the session data if the user agent changes, but that doesn’t prevent a user from successfully logging in from multiple devices, that simply makes sure the cookie data is coming from the same browser. What do you think? I’ve been thinking about allowing the application to be logged in from multiple devices at once, but don’t know if this is considered insecure by many.