yea it simulates keypresses somehow, like how autohotkey or xdotool does. i should probably throw out a disclaimer before i hype it up too much though :p

it used to work a lot better back when most sites had both the username and password input box on the same page. sites like google have started putting them on different pages now which confuses things. the sequence of keys it sends is {USERNAME}{TAB}{PASSWORD}{ENTER} so it doesnt really have awareness of the actual input box elements the way a browser extension would

the quick fix for this is to just use the separate hotkeys ctrl+1 to autotype the username and then ctrl+2 for the password