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The Evolution Of CAPTCHA – How An Anti-Spam Measure Has Grown?

‘CAPTCHA’ is the anti-spam measure that you see on most sites that let you post content these days. These are images that usually hide text or numbers in a mess of colors and strange wavy lines, which then challenge you to identify where the letters or numbers are and type them out correctly. CAPTCHA stands for ‘Completely Automated Public Turing test to tell Computers and Humans Apart’ (you can see why they went with an acronym), a Turing test of course being a test designed to distinguish humans from scripted programs.

Originally, Turing tests were designed to test the ability of machines to fool humans – if a computer could pass a Turing test, it would be considered a feat of AI ingenuity and a milestone in programming. As CAPTCHAs (a term coined in 2000), the test is instead used as a filter to prevent automated ‘spam bots’ or ‘brute force’ hacking tools from using online forms.

Traditionally, CAPTCHA is a necessary evil – somewhat annoying for both the user and the webmaster to have to go through. Over the years, though several innovations have seen it grow to become something much more. These days CAPTCHA can actually be an asset to your site, beyond its spam-filtering capabilities. Here are some of the more impressive examples of what CAPTCHA can now do…


KeyCAPTCHA enhances the regular system by monetizing it. It does this by inviting users to complete an interactive task (rather than copying symbols) which include things like completing puzzles and at the same time adding advertising.

The puzzles themselves are actually more effective according to user reports than the symbol sequences, while the chance for extra monetization will likely appeal to many bloggers.

2.) Puzzle CAPTCHA:

Like the sounds of having a puzzle for your spam protection but don’t need the monetization? Then Puzzle CAPTCHA, as the name suggests, is the ideal solution for you.

Alternatively, you could also try PLAYTHRU which similarly ‘gamifies’ the process.


ReCAPTCHA from Google is an incredibly smart innovation, which provides the visitors with two tasks. One involves deciphering the usual obscure sequence of symbols, while the other is formed of photographs of street signs, house numbers and even text from books. This way, the test not only prevents spam, but also gets the visitors to serve a helpful role at the same time – helping Google with their efforts to convert books into digital texts as well as to populate their maps service with accurate data. This is crowdsourcing at its smartest.

With Mailhide, you can also protect the e-mail addresses of your users (if they’re required).

4.) Motion CAPTCHA:

If you ever remember playing those games where you had to move a ring carefully around some wire without setting off a buzzer, Motion CAPTCHA is a very similar concept. It’s ideal for touch screens, it’s quicker than tying and it’s something memorable to add to your site. All that plus it’s a great pun. You can see a demo here.


ASIRRA is a Microsoft Research project that is perhaps the cutest CAPTCHA solution out there. This one asks users to identify pictures of dogs and or cats in a set. It’s a collaboration with that will bring a smile to your visitors’ faces…


NUCAPTCHA improves on the usual theme by using videos rather than static images to provide the questions. This not only makes the task harder for ‘bots’ to counter, but it also means the text can be easier for humans to read.

So there you have it, a whole host of innovative CAPTCHA solutions! If you’re going to be forced to test your visitors, then you may as well make it enjoyable, useful, cute or profitable in the process!

Krupesh PadaveAbout the Author:

Krupesh Padave is an internet marketing analyst at WebSmith Technologies, an online marketing agency helping many online brands get more traffic and sales from various internet based channels.. When he isn’t searching for quirky ways to rev up the marketing world, he enjoys writing about its nitty gritty’s.

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