This plugin is not maintained an causes errors - it's not for productive use!
CustomField plugin for Joomla! Contactform and Userregistration Context. Includes a Google invisible recaptcha Field.
Install the plugin with the Joomla installer
activate the plugin and setup the secretkey in the plugin parameters
Add the field in com_user or in the context form of com_contact
- to see if your field works, check your form and see if there is the Google invisible recaptcha badge in the right corner of your website.