How do 3rd party websites know which Twitter account I am logged in to?


I’ve just set up several Rebelmouse accounts for different Twitter accounts I manage. As a Twitter app developer myself, I don’t understand how Rebelmouse knows which Twitter account I am logged in to.

At first I thought it was cool and I might want to use this in one of my own apps.

But I have since found it to be extremely inconvenient that they do this, because I can no longer choose which accounts I can use at a given time. For example, it seems that if I am logged in to Twitter account “A” and wish to use Rebelmouse, I have no other choice but to log in to Rebelmouse account “A”, or use another browser. If I log out of Twitter account “A” Rebelmouse knows this and I am free to use or create another Rebelmouse account.

How do they do that and how can I circumvent it?