Captcha

A Captcha is a program that protects websites by generating and grading tests that humans can pass but computer programs cannot. For example while registering a new email id for yahoo a box with distorted text will be displayed which the humans can read but current computer programs can't.



The term Captcha ( Completely Automated Public Turing test to tell Computers and Humans Apart ). Some Captcha's now use pictures instead of words where the user is presented with a series of pictures and asked what is the common element among all of the pictures. By entering that common element, the user validates the transaction and the computer knows it is dealing with a human and not a bot.