On Google Chrome, with adblock on, without my Google account signed in, in a new incognito tab with no extensions, I have the experience of it being invisible.

On Google Chrome, with adblock on, without my Google account signed in, in a new incognito tab with no extensions, I have the experience of it being invisible. When I go back to the same site on Firefox, logged onto my Google account, no adblock on, no privacy options on, I have to identify dozens of photos. As far as I can tell, it just checks to see if your browser is Google Chrome to give you your score.