ReCAPTCHA has a "Security Preferences" parameter where you can set the level of difficulty of the test. If you set it to "Most Secure" most or all users are pre

ReCAPTCHA has a "Security Preferences" parameter where you can set the level of difficulty of the test. If you set it to "Most Secure" most or all users are presented with the multiple image identification scenario you describe. Easiest will simply present the "I am not a robot" checkbox modal which does some browser fingerprinting and other tests in the background. I believe there is also a heuristic that determines the difficulty of the test to present users if you leave the setting on the default medium difficulty. Could be mistaken, but this is my takeaway from implementing reCAPTCHA a few times.