Tasks come in two types: simple and additional. Simple tasks include the “I’m not a robot” checkbox, slider, and the invisible CAPTCHA:
Checkboxes are a common task and therefore familiar to users.
Sliders are a good choice for mobile devices.
The invisible CAPTCHA allows you to check a user without showing them a checkbox or slider. Users whose requests seem suspicious will see an additional task. There are three types of additional tasks:
text recognition,
silhouettes,
kaleidoscope. These tasks are a bit harder for humans, but filter out robots more efficiently. Tasks with images do not require localization and work if your users do not know Russian and English. Moreover, these tasks don’t require a keyboard. Please note that the slider, kaleidoscope, and silhouettes features are at the Preview stage.