Scanned text is subjected to analysis by two different OCRs. The waviness and horizontal stroke were added to increase the difficulty of breaking the CAPTCHA with a computer program.

Operation ReCAPTCHA v1 (human-assisted OCR) Īn example of how a reCAPTCHA challenge looked in 2007, containing the words 'following' and 'finding'. An early CAPTCHA developer, he realized 'he had unwittingly created a system that was frittering away, in ten-second increments, millions of hours of a most precious resource: human brain cycles'. The reCAPTCHA program originated with Guatemalan computer scientist Luis von Ahn, and was aided by a MacArthur Fellowship. It works with Project Gutenberg to digitize public domain material and uses methods quite different from reCAPTCHA.

In 2014, Google pivoted the service away from its original concept, with a focus on reducing the amount of user interaction needed to verify a user, and only presenting human recognition challenges (such as identifying images in a set that satisfy a specific prompt) if behavioral analysis suspects that the user may be a bot.ĭistributed Proofreaders was the first project to volunteer its time to decipher scanned text that could not be read by optical character recognition (OCR) programs. National Telecommunications and Information Administration's digital TV converter box coupon program website (as part of the US DTV transition). The system was reported as displaying over 100 million CAPTCHAs every day, on sites such as Facebook, TicketMaster, Twitter, 4chan, CNN.com, StumbleUpon, Craigslist (since June 2008), and the U.S. The system helped to digitize the archives of The New York Times, and was subsequently used by Google Books for similar purposes. It was acquired by Google in September 2009. reCAPTCHA was originally developed by Luis von Ahn, David Abraham, Manuel Blum, Michael Crawford, Ben Maurer, Colin McMillen, and Edison Tan at Carnegie Mellon University's main Pittsburgh campus. The verification prompts utilized pairs of words from scanned pages, with one known word used as a control for verification, and the second used to crowdsource the reading of an uncertain word. The original iteration of the service was a mass collaboration platform designed for the digitization of books, particularly those that were too illegible to be scanned by computers. Since version 3, reCAPTCHA will never interrupt users and is intended to run automatically when users load pages or click buttons. Version 2 also asked users to decipher text or match images if the analysis of cookies and canvas rendering suggested the page was being downloaded automatically. The original version asked users to decipher hard to read text or match images. ReCAPTCHA is a CAPTCHA system that enables web hosts to distinguish between human and automated access to websites.

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