View source for ReCAPTCHA

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[[Image:Modern-captcha.jpg |thumb|290px|An example of a reCAPTCHA challenge]]
'''reCAPTCHA''' is the process of utilizing [[CAPTCHA]] to improve the process of [[digitizing]] books. It takes scanned words that [[optical character recognition]] software reported undetectable and presents them for humans to decipher as CAPTCHA words alongside words recognized by the computer.

== How it works ==
In order to verify that humans can decipher these previously undetectable words correctly, two words are displayed instead of the standard one word. One of these words is generated in the usual CAPTCHA form, and only the other word is undetectable. If the users solve the usual test for the first word, it is assumed that they were also correct about the other previously undetected word. Nevertheless, more than one user has to verify the other word in order for it to be considered truly solved.

== How it is provided ==
reCAPTCHA tests are taken from the central site of the reCAPTCHA project<ref>[http://recaptcha.net The reCAPTCHA project] - part of the [[Carnegie Mellon School of Computer Science]] at [[Carnegie Mellon University]].</ref> as they are supplying the undetected words. This is done through a Javascript API with the server making a callback to reCAPTCHA after the request has been submitted. The reCAPTCHA project provides libraries for various programming languages and applications to make this process easier. reCAPTCHA is a free service, except for users who would require a prohibitive amount of bandwidth.

==Notes==
{{reflist|2}}
*reCAPTCHA has the same goal as [[Distributed Proofreaders]], though DP uses conventional proofreaders
*reCAPTCHA press release: {{cite web |url=http://www.cmu.edu/news/archive/2007/May/may24_recaptcha.shtml |title=May 24: Carnegie Mellon Project Boosts Book Digitization Efforts - Carnegie Mellon University |accessdate=2007-06-23 |format= |work=}}
*[http://news.bbc.co.uk/2/hi/technology/7023627.stm Spam weapon helps preserve books] &mdash; BBC news report by Paul Rubens, 2007-10-02.

== External links ==

*[http://recaptcha.net/ The reCAPTCHA project]

[[Category:Artificial intelligence]]
[[Category:Computer security]]
[[Category:Crowdsourcing]]

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