Here's the new version:
"On websites using this new API, a significant number of users will be able to securely and easily verify they're human without actually having to solve a CAPTCHA. Instead, with just a single click, they'll confirm they are not a robot." Here's an example of site that uses the new API.
So instead of solving CAPTCHAs with distorted text you can just click a box. But how does this work? Google uses some sophisticated risk analysis algorithms that "actively consider a user's entire engagement with the CAPTCHA — before, during, and after — to determine whether that user is a human."
If the risk analysis engine can't confidently predict whether a user is a human or a bot, you'll see a regular CAPTCHA. For example, I opened this page that uses the new reCAPTCHA in a new Chrome incognito window and Google displayed a regular CAPTCHA.
Google also tests other simplified CAPTCHAs that are better suited for mobile devices. For example, one of the CAPTCHAs asks you to select images that show a cat.
Another experiment asks you to pick your favorite color.
One of the reasons why Google started to find alternatives to traditional CAPTCHAs is that "today's Artificial Intelligence technology can solve even the most difficult variant of distorted text at 99.8% accuracy. Thus distorted text, on its own, is no longer a dependable test."