The system plugin uses well known anti-spam tests that do not require user action. This way you can protect your website from spam bots with methods that are better for website usability and accessability than Captchas.

Aimy Captcha-Less Form Guard is easy to use and configure: Enable the plugin, configure your preferred methods and select Aimy Captcha-Less Form Guard in Joomla's global configuration dialog as default Captcha.