How to add reCAPTCHA site key?

How to add reCAPTCHA site key?

I'm getting an error on my site saying: ERROR for site owner:

Invalid domain for site key

There's no need to enter site key. You just have to add captcha in your form.

Example:

I would also recommend re-adding the captcha in your form if in case you still get the same error.

You can also switch to JotCaptcha if you don't like using Google reCaptcha.