Google Analytics + Typekit: how do tehy identify you?

Hello,

I’m very curious to understand how sites such as G Analytics and Typekit know your website is yours. I mean, since they’re using only js to accomplish their respective tasks, my guess is it could be very easy to pretend you’re someone else to those services. Is JS doing some koind of Oauth? What are the principles behind web services reached through JS and authentication?

:slight_smile: