It is very simple to add captcha to html form.
Include the following div in the form where we have to include capcha
<div id="recaptcha-div" class="g-recaptcha" data-sitekey="DATA SITE Key" ></div>Data site key is recaptcha key which we obtain after registering domain and site in reCAPTCHA admin console with Google account.A reCAPTCHA key is a unique alphanumeric string of 40 characters.
And include following js in our page
<script src="https://www.google.com/recaptcha/api.js"></script>We can set two attributes to grecaptcha depending on the design
data-size =”compact” or data-size=”normal”
When data-size =”compact” is applied,captcha section will be square type and section will be rectangle type if data-size is set to normal