I have heard (I can't remember where I heard this unfortunately) that some types of captchas don't verify that the user is human by having them click on the correct images but rather examine the users pattern of mouse movements prior to, or while, completing the captcha puzzle. Or at least, I have heard it claimed that mouse movements are used in addition to the completion of the puzzle to determine if the user is human. I would like some evidence that this is, or is not, the case.

  • As is, this is not a good question for this site, which requires a notable claim. "I have heard (I can't remember where I heard this unfortunately) ..." does not qualify as a notable claim. This could be make into a notable claim by quoting notable (widely viewed) sites that claim Google's ReCaptcha uses mouse movements, and asking whether this is true. Unfortunately, there's no knowing; Google keeps its methods privately held so as to avoid feeding the bots. The "bot or not" problem is notoriously hard to solve. Dec 27, 2020 at 11:35
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    Also see How does Google's “No Captcha reCaptcha” work? at the Information Security StackExchange and How does Google reCAPTCHA v2 work behind the scenes? at StackOverflow. Dec 27, 2020 at 11:52

1 Answer 1


There is a system developed by Google, called "No CAPTCHA" or "reCAPTCHA". With that system you do not need to click on pictures with cars, traffic lights or distorted text. Instead there is only a box to tick. It works by tracking mouse movements. Google claims it is very secure, as it checks to see if the movements look like a human. If it's not sure, it reverts to the old picture mechanism.

For more details, see http://qnimate.com/how-does-googles-no-captcha-recaptcha-work/

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    That type almost always reverts for me. With this info, I chose to believe Google interprets me as "superhuman".
    – user11643
    Dec 27, 2020 at 9:44
  • @fredsbend: Same here, so I guess that makes two of us...
    – Fizz
    Dec 27, 2020 at 10:17
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    This answer might or might not be correct. Some, such as the linked site in this answer, have speculated that the ReCaptcha box uses mouse movements, but that is just speculation. I doubt this question can be answered in manner suitable to skeptics.SE because Google intentionally has not disclosed what technologies it uses to solve the "bot or not" problem. Dec 27, 2020 at 11:50
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    @DavidHammen The code to capture mouse motion would have to run client-side, so it would be possible to determine whether it's being captured or not, though not what happens to it on Google servers.
    – benrg
    Dec 27, 2020 at 17:56
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    @shoover - It would go to the fallback mechanism of showing pictures of dogs and cats.
    – JohnFx
    Dec 28, 2020 at 20:06

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