Web Property Prefix
If you leave the Web Property Prefix blank, you'll see Activities data for the domain you are tracking with Google Analytics (e.g. example.com). If you also wish to see Activities data for properties such as your YouTube channel, enter your prefixes here; for example, youtube.com/example. Make your prefix as specific as possible (i.e. do not simply enter youtube.com). Activities data is only shown for properties from which your domain has received hits.
Please note that if you enter one or more prefixes (such as youtube.com/example), you must also enter your primary domains (e.g. example.com). Otherwise, Activities data for your primary web property will be filtered out.