how to add recaptcha to contact form html code example

Example 1: embed recaptcha in html

<div class="g-recaptcha" data-sitekey="6LcePAATAAAAAGPRWgx90814DTjgt5sXnNbV5WaW"></div>

Example 2: embed recaptcha in html

<script src='https://www.google.com/recaptcha/api.js'></script>

Example 3: contact form 7 recaptcha

Only for tick checkbox
https://wordpress.org/plugins/contact-form-7-simple-recaptcha/