Add reCAPTCHA to Contact Form 7
UPDATE 12/30/18: Google has released reCAPTCHA v3.
See this post for how to re-register your site and get the new API keys http://bit.ly/2BSoGUi
Get superior spam protection on your contact form. It's easy to add Google's reCAPTCHA to Contact Form 7.
Just register your site with reCAPTCHA, get your keys, and put them into Contact Form 7's Integration.
Then, add the recaptcha shortcode to your form.
That's it!
Be sure to visit https://www.blogaid.net for more tips and tutorials.