ReCAPTCHA is a free CAPTCHA service that helps to digitize books, newspapers, old time radio shows and protects you from spam.
CAPTCHA is a program that can determine whether the user typing is a human or a computer assisted software or device.
CAPTCHAs are used by website owners to prevent mail abuse from "bots" or automated programs designed to generate spam.
The distorted text generated by this programs make it hard and even impossible to read by automated scripts or bots and only humans can properly interpret the messages they display.
How it works
Optical Character Recognition or OCR is used to transform physical books into its corresponding digital format pictures that can be used by reCAPTCHA.
reCAPTCHA improves the process of digitizing books by sending words that cannot be read by computers to the Web in the form of CAPTCHAs for humans to decipher. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.
The CAPTCHA system works by sending each word that cannot be determined by OCR to the user, along with another word for wich the answer is already known by the system.
The user will be asked to read both entries and if one is correct the system will assume that the second one must be correct also.
The system then sends the same CAPTCHA to a number of other people to determine if the first answer was right.
ReCAPTCHA is a easy software utility that helps digitize books, newsletters and helps protect users from spam bots and automated scripts.
It is easy to set up and use, even if the user doesn't have programming skills and it is a great way to protect your site or e-mail address while giving something back to the community.
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