reCAPTCHA is provided by Google, and we use reCAPTCHA v2 Checkbox. You can find more details about it at this link.
Create an API key pair
To start using reCAPTCHA, you need to sign up for an API key pair for your site. The key pair consists of a site key and secret key. The site key is used to invoke the reCAPTCHA service on your site or mobile application. The secret key authorizes communication between your application backend and the reCAPTCHA server to verify the user's response.
You will then receive a site key and a secret key.
Configure in Casdoor
Create a new provider in Casdoor.
Select the category as Captcha and the type as reCAPTCHA. You need to provide the site key and secret key created in the previous step.
You can click the Preview button to see the style of this captcha.
Apply in the application
Edit the application you want to configure in Casdoor. Select the provider you just added and click the Save button.