A user connects to my web application,I grab some sort of device ID through W3C standard protocols,The user logs in,I can then identify this specific unique device owned by the user (not just iPad - I'm looking for iPad3_2C38TY43058 or even just John's iPad).This would let me design my web application to treat logins from this device in a specific way, know which of John's 5 devices he's logged in from, etc. Is there such a protocol? Is there any method of identify a specific device as described?
Is there a protocol for identifying a users's device?
web applications
Web browsers do not send any identifier that is specific to a device. They send the User-Agent header which will generally tell you the name of the browser, version of the browser, and often the type of device.You can set a cookie the first time that you see a visitor with a unique device ID in it.   The user will send that cookie back on every subsequent page visit.   Cookies sound exactly like what you want here.   They are generally not shared between devices.