If suspicious behavior occurs, the system presents a challenge, often requiring the selection of specific images. The No CAPTCHA reCAPTCHA system is more user-friendly compared to traditional CAPTCHA.

CAPTCHA puzzles – which may involve text, image, audio, or behavioral challenges such as clicking checkboxes – are ubiquitous online. Google acquired the reCAPTCHA service in 2009, two years ...

Through analyzing over 3,600 users, the researchers found that solving image-based challenges takes 557% longer than checkbox ...