Understanding Cross Device Measurement and the User-ID

A User-ID view contains only data hits in which the User-ID was set. Think of it as a filtered view.

One of the fundamental new features of Universal Analytics is user-centric measurement. This includes measurement across multiple devices – computers, smart phones, tablets, kiosks, etc. But this change introduces a number of new challenges for analysts and marketers. In order to do cross device measurement you need to understand some of the challenges and limitation. […]