You can use the most popular captcha control "reCaptcha" now!

We suggest you need create an account from here
(Note: the control will still work if you don't sign up with reCaptcha, but much secure if you do this)

And then create you own domain from

After that, You will get a public and private key.

And then, you need copy this key to the "Advanced Settings" when you create it


You can also choose different theme for it from the "Advanced Settings"
(Default theme is "Red")