But in shopify you can not implement a google recaptcha or develop a working captcha solution using the very limited theme editing capability.
So you can see the action url is set to https://www.google.com . If a spam bot only loads html and submit the form, he will be taken to google.com 😀 😀
So its not visible to the human visitors and we can guess that they will not be able to fill it. But as spam bots use programs to submit forms , they will see this as a regular field and most likely they will fill this field as well. On shopify backend I created a webhook for customer creation and wrote an app that will check if the user has filled this field or not. If the user/spam bot fills this field and submit the registration form, the app will immediately delete that user. So your website is safe from spam registrations.
You can check the working demo here http://megamenu-3.myshopify.com/account/register
If you want to us to implement this solution for your shopify store simply fill the form below and we will contact you asap.