We are familiar with Captcha. These are those annoying images with characters or numbers that we need to type in the box below to confirm we are not robots.

For us, it’s a minor annoyance. But for Captcha providers it enables a bigger task (than just preventing automated bot submissions) through our collective efforts.

Luis von Ahn is the inventor of Captcha was interviewed on NPR – How I Built This Podcast recently.

He tells us the interesting story of how he initially created Captcha to solve Yahoo’s email spam issues because of bot auto-signups. He then got an opportunity to provide the same technology to a relatively unknown company back then – Facebook.com.

In no time, with the quick growth of Facebook Signups (and his Captcha Usage), he decided to put to use and monetize his invention in a unique way.

At about the same time a popular newspaper giant in the US was looking to digitize all its older newspaper editions and put it on the net. They could have employed people to manually type all the content, but that would have taken a lot of money and more importantly – a lot of time.

Luis von Ahn approached them and offered to digitize their content using his Captcha technology. This was cheaper for the vendor and faster.

How much faster, do you ask? Well, one year’s newspaper content was digitized in just ONE WEEK. That too automatically by people filling out Captcha at random websites!

Read that again. Pure brilliance.

I know you are wondering how did he ensure accuracy with his system? After all, random people were typing stuff and they were bound to make mistakes.

To solve this issue, the same image (same text) was given to multiple people and only when the input from three or more people matched, it was accepted.

It seems this technology was later bought by Google and they are using it to digitize books. The creator went on to make DuoLingo – the popular free language learning app. How he monetized this initiative is another interesting case study.

Listen to the entire story from this NPR Podcast episode. It’s worth your time.