For questions about the reCAPTCHA service, designed to protect against spam and abuse by blocking bots while allowing valid users to pass through with ease.

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There is difference between how humans move the mouse versus how bots do. Google's reCaptcha system takes advantage of the above fact to predict whether you are a human or not. Google's reCaptcha system has a predictive model trained with sample mouse movements made by both humans and abusive bots.