One of the biggest challenges you have to face when providing a form to your website is spam. If you use Contact Form 7, you can combat spam and other automated abuse types by protecting your form with reCAPTCHA. Contact Form 7 supports integration with reCAPTCHA to provide protection to your forms. The reCAPTCHA version used by Contact Form 7 (starting from version 5.1) is v3 (reCAPTCHA v3).
reCAPTCHA v3 itself works in the background so that after adding it to your Contact Form 7, you won’t see a physical verification like reCAPTCHA v2 which typically requires users to make a confirmation by ticking an “I’m not a robot” checkbox or selecting a number of images.
You need a Site Key and a Secret Key to integrate reCAPTCHA. To get them, visit the website of reCAPCTHA. Click the Admin console button ton the top-right corner and login with your Google account.

Click the plus button to register a new site (you can use a single domain to get multiple Site Keys and Secret Keys).

Enter the label and your domain (without “http://” or “https://”) and accept the ToS (Terms of Service). On the reCAPTCHA type section, select reCAPTCHA v3. Click the SUBMIT button.

On the next page, copy the Site Key and Secret Key.

Now login to your WordPress dashboard and go to Contact -> Integration and click the Setup Integration button on the reCAPTCHA section.

Paste the Site Key and Site Secret you have copied to the respective fields and click the Save Changes button.

That’s it. Your form is now protected by reCAPTCHA. As mentioned, reCAPTCHA v3 works in the background so you will see no checkbox beneath your form. This reCAPTCHA version works based on user interaction with your website. You can read this blog post to learn more about how reCAPTCHA v3 works.
After several days from the installation, you can return to the reCAPTCHA dashboard to check the stats. Simply select your website from the dropdown menu to see the stats.

I get a lot of mails from Robots and it’s very annoying. This post has really helped me a lot.
Great article! We’ve been using Contact Form 7 but not a recaptcha, but this article explains it’s benefit. Will surely apply it on our webstore, thank you!