Google has been testing a new version of reCAPTCHA that makes it easier for users to prove that they're actually human and not bots. The new reCAPTCHA no longer uses a CAPTCHA, so you no longer have to deal with blurry house number images or squiggly words from scanned books.
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."
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.
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.