问题
hello i see facebook is using recaptcha, but somehow in their register page, they can show one word of captcha instead of two, and then i notice that repcatcha validate only the first word, and the second word acts as a dummy, the question is can we somehow tell the recaptcha to just show one word ? rather then two ?
回答1:
No.
But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct.
来源：https://stackoverflow.com/questions/4768672/one-word-recaptcha