If you want to enable Captcha to Events Booking to prevent spams, please follow the instructions below:
When you do that, captcha will be enabled on Registration Form, Submit Event Form, Invite Friend Form to protect Events Booking from being spammed
Some of third party captcha plugins like Recaptcha Version 3, HCapcha won't work for group registration in Events Booking. So if you use Group Registration, please just use invisiable repcaptcha plugin comes with Joomla core. Or you can use our JD Captcha Plugin