Today the Internet world is not confined to a class of people or things. This virtual world consists of information in varied formats, entertaining people in many different ways. There is an immense rise in the number of internet users from the past few years. Also there is a hike in the number of internet spams. So there comes always the security or protection issue. And CAPTCHA is one aspect in protecting Internet world.

All of us who uses internet for learning , for entertainment , for fun knows CAPTCHA well . It is something which you see during your Gmail , or any website sign up where you’re asked to enter some kind of distorted texts or asked to select some images, without solving which you cannot signup. Solving CAPTCHA is sometimes difficult but most of the time its easy to clear. Do you know why do we need to confirm ourselves as humans ? Yes we need to confirm ourselves as humans because its not only we who surf the internet, there are robots or bots which roams on the web trying to hack or find vulnerabilities of websites and try to spam the websites. So to protect from them websites implement CAPTCHA test.What-is-captcha

CAPTCHA is an acronym which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart” is a test to determine whether or not the user is human, by presenting questions or puzzles which humans can understand but bots(A computer programme ) cannot. And today we have wide variety of CAPTCHA formats making much more complicated for bots to decode. The Captcha works according to reverse Turing test , an opposite of turing test ( Human judges the computer ) proposed by Alan Turing . At present CAPTCHA’s are widely used to filter Spam on websites. As day by day technology is getting more sophisticated , decoding of captcha’s is also becoming simple for bots. In order to protect the web world, CAPTCHA’s are getting modified day by day in different syles and formats to ensure high protection.

Lets see here some different types of CAPTCHA.

Different types of CAPTCHA

1.Distorted word CAPTCHA

In this type users are presented with some distorted texts, if one cannot understand them clearly they can reload them to get simpler one. You can also clear the Captcha test  by listening to the audio. Distorted word format is the most commonly used type.Re-captcha


In this type of CAPTCHA user need to solve some simple arithmetic question often the text can be simple or distorted.



In this type user finds characters in 3D format. Other type of 3D CAPTCHA involves in adjusting the blurred part of the image to make it complete.


Also check :

4. Image CAPTCHA

In this case users need to select the asked image to clear the test. Sometimes it is shown with some image and you’re asked to select the images of same type or containing similarity from the given image.


5.Jigsaw CAPTCHA

In this type of test you are given an image with missing parts,  you need to arrange the missing parts just like in jigsaw puzzle to clear the test.


The above are only the ones which are in use currently and when they are once be able to deciphered by the bots then a new style need to be devised and implemented to ensure protection. But whatever the CAPTCHA may be its only a computer programme but when there human labour is used to do that job for few pennies to make the spam then this CAPTCHA’s can’t do anything to avert that but still there are some methods available for protection. So this is a brief story about CAPTCHA , hope you enjoyed the article.

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One thought on “What is CAPTCHA , why it is used ?”
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