What is Captcha ?

What is CAPTCHA?

  • CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart.
  • A challenge question
  • First used by Altavista in1997 but officially in 2000 by Luis Von .


Since the dawn of the Internet, people have tried to abuse websites for both sport and profit. As the abuse became profitable, the scale of abuse grew using automated software (sometimes referred to as bots). To prevent bots from overrunning sites with spam, fraudulent registrations, fake sweepstakes entries, and other nefarious things, publishers responded by testing users to see if they were human or not.

CAPTCHA implementations can be found on more than 3.5 million sites globally, and human beings solve CAPTCHA implementations more than 300 million times a day.


Google Lunches a new reCAPTCHA technology to protect your security and sites from third party to hack.reCAPTCHA is a free service that protects your website from spam and abuse. reCAPTCHA uses an advanced risk analysis engine and adaptive CAPTCHAs to keep automated software from engaging in abusive activities on your site.


Captcha have several applications list which are used as-

  • Website Registration
  • Online polls
  • Newsgroups, Blogs etc…
  • Reducing SPAM



Some Examples of CAPTCHA:

Text Based Captcha-


Graphics based Captcha:

  • Advanced security System.
  • Ease of use
  • Creation of values

Audio Based Captcha:


Distinguishes between a human and a machine
Makes online polls more legitimate
Reduces spam and viruses
Makes online shopping safer
Diminishes abuse of free email account services


Sometimes very difficult to read
Are not compatible with users with disablilities
Time-consuming to decipher
Technical difficulties with certain internet browsers
May greatly enhance Artificial Intelligence



Awadhesh Kumar

Jain Software Developers