The conceit of Humans Not Invited is essentially a reverse CAPTCHA. Visitors to the site are greeted with a vision test not unlike the ones you’ve done before, but instead it’s filled with seemingly indistinguishable blue and gray blurry boxes. When I tried, I was prompted to “select all squares with selfie sticks.”
Most humans, like me, will fail to decipher the hidden selfie sticks and will be shown a message that says “YOU’RE A HUMAN. YOU’RE NOT INVITED.”
To the human eye these boxes appear indistinguishable, a specially programmed bot can spot out the correct image simply by identifying a handful of pixels, according to the project’s creator, Damjanski, (his real name is Danjan Pita).