ReCAPTCHA: Stop Spam. Read Books.

2 Comments June 20, 2007 1161 Views

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Do you guys know what a captcha is? Most bloggers would easily know the answer to this but for the ordinary person, it might sound like a million dollar question for a quiz show.

You’ve probably seen one but you just don’t know what its called. Captchas are those distorted letters and numbers that you see at the bottom of web registration forms. These are used as a form of verification and also to prevent spam abuse. Btw, CAPTCHA is an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart” and is trademarked by the Carnegie Mellon University.

Here’s a little trivia: About 60 million CAPTCHAs are solved by humans around the world every day.

There are so many types of captchas available and one of them is reCAPTCHA. So what is reCAPTCHA?

reCAPTCHA is not your ordinary captcha. Aside from keeping your website or blog free from spam, it also helps in digitizing books. How?

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.

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.

Why use reCAPTCHA? It’s easy to use, secure and by using reCAPTCHA, not only will you fight spam but you can also help in digitizing books. Btw, I forgot to mention that reCAPTCHA is free and available as plugins for the following applications:

• WordPress
• MediaWiki
• phpBB
• Movable Type
• Drupal
• Symfony
• Typo3
• NucleusCMS
• ColdFusion

Check out or download reCAPTCHA.

Note: Installing captchas can cause problems with trackbacks. If you decide to install a captcha, check if your trackbacks still works.