I usually hit the right one on the first or second try. The hostname usually tells you what it does. Say the images of users on github.com are broken. I open u

I usually hit the right one on the first or second try. The hostname usually tells you what it does. Say the images of users on github.com are broken. I open umatrix and think 'Hmm.. which host could they load them from?'. I enable 'githubusercontent.com' and voila! The user images appear.