The difference between reCAPTCHA v2 and v3

CAPTCHAs are a common test on the web and are designed to differentiate between actual users and bots.

Google introduced reCAPTCHA v3, hoping to reduce the number of challenges a user might see.
As bots that try to pass as actual humans become more sophisticated, Google has released new versions of its reCAPTCHA API.
The most recognized version of this test involves typing in distorted text, with more current forms asking users to identify objects in images.
The old reCAPTCHA system was pretty easy, just a simple “I’m not a robot” checkbox would get people through your sign-up page.

The new version is even simpler, and it doesn’t use a challenge or checkbox. It works invisibly in the background, somehow, to identify bots from humans.
Google doesn’t go into much detail on how it works,
only saying that the system uses “a combination of machine learning and advanced risk analysis that adapts to new and emerging threats.”
With reCAPTCHA v3, Google is improving the experience even more, with the API returning a score between 0.0 and 1.0 that ranks “how suspicious an interaction is.”

What’s the difference?

The “I’m not a robot” Checkbox requires the user to click a checkbox indicating the user is not a robot.
This will either pass the user immediately (with No CAPTCHA) or challenge them to validate whether or not they are human.
This is the simplest option to integrate with and only requires two lines of HTML to render the checkbox.
reCAPTCHA v3 allows you to verify if an interaction is legitimate without any user interaction.
It is a pure JavaScript API returning a score, giving you the ability to take action in the context of your site:
for instance requiring additional factors of authentication, sending a post to moderation, or throttling bots that may be scraping content.

Error when sending a message

If you send several “test” messages one after another through the contact forms on your website, the security algorithm will identify you as a spam bot and you will see this message (in the picture to the left). Other visitors on your website will still be able to send you a message.

This error will remain only on your computer or phone. It should not scare you. The error will disappear in a few days when the device cache is updated.