This site is using reCAPTCHA v3, Google’s Invisible reCAPTCHA. It monitors and analyzes user behavior to distinguish between real humans and bots.
Traditional CAPTCHAs require humans to solve visual puzzles or to read distorted characters; the new reCAPTCHA works in the background and does not require puzzles or even the “I’m a human” check box.
Purdy cool stuff!
https://cloud.google.com/security/products/recaptcha