They have plugins for many types of software (Wordpress, Drupal, Mediawiki...) and an API for many languages (PHP, PERL, ASP...)."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.
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