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CAPTCHA on Custom Forms
Additional information relating to CAPTCHAs on forms + link to Google documentation
CAPTCHA v3 was added back to our custom forms in the March 2022 release. CAPTCHA is built-in to the form page and hidden but should be preventing most spam. No solution can prevent 100% of all spam.
The makers of spam bots are always improving them to get pass CAPTCHA. As long as contact forms exist on a site, someone will try to send spam through them, just like email will always have spam. If people didn't click the links in the spam, the scammers would realize it's not a viable business venture and likely stop sending it.
Here’s Google’s explanation of how it works. https://developers.google.com/search/blog/2018/10/introducing-recaptcha-v3-new-way-to