Go to System → Settings → General
Enter Google reCAPTCHA Site Key and Secret to enable Google reCAPTCHA. Google reCAPTCHA ensures that a real human is interacting with the site forms.
If both keys are empty then default built-in captcha image used.
Supported reCAPTCHA v2 and v3. To enable reCAPTCHA v3 please generate v3 keys and set to On the Enable reCaptcha v3 setting.
reCAPTCHA v2 requires users and customers to click the “I’m not a robot” checkbox and possibly select specific images to complete a challenge.
reCAPTCHA v3 verify requests with a score based on Google algorithm.