https://mentalfloss.com/article/575112/why-are-bots-unable-check-i-am-not-robot-checkboxes

The dreaded reCAPTCHA text box has been hated by many. It exists to prevent spam submissions to websites. Over the years, the Google technology has evolved from entering text that was intentionally garbled to a checkbox that may or may not ask you to identify a traffic light or bicycle in an image. Released in October, 2018 [1] , reCAPTCHA v3 now skips the checkbox entirly. It only presents you with a challenge if it thinks you’re not real. This article explains the technology behind this aspect of the spam arms race.