Anonymous B joined in and replied with this 10 years ago, 10 minutes later[^][v]#725,489
machine learning and by virtue of running on google's server. if you solve a captcha on site 1, and dont clear cookies for google captcha, it will remember that and when you go to another site you also wont have to do a captcha. it also runs a ton of very complicated checks the moment the page load to determine if its running in an automated/bot environment. it also looks at the way the cursor moves.
Anonymous A (OP) replied with this 10 years ago, 4 minutes later, 14 minutes after the original post[^][v]#725,490
@previous (B)
wow that was a great answer, thanks.
Green !BEERiVqJJw joined in and replied with this 10 years ago, 12 hours later, 12 hours after the original post[^][v]#725,579