At a recent event a developer working for one of the top US mobile operators told me that “an HTML5 Web app can obtain unique device identification information on any Android device it runs in.” The comment was about Web-native apps in cell phones, not HTML5 running inside a WebView in a Java app.
How can this be done? Unfortunately, I don’t have access to the developer to ask.
At a minimum, I would consider any of the following to be uniquely identifying the device: ANDROID_ID, phone number and IMEI for GSM or MEID/ESN for CDMA. There may be other types of identifiers I’m not familiar with.
You can’t get those details from the browser. I’d be concerned if you could!
You could use cookies to uniquely identify a user, but there’s no way to personally identify them. Even then cookies can be cleared.