What Is It?

A CAPTCHA (which stands for Completely Automated Public Turing Test to Tell Computers and Humans Apart [sometimes spelled all lowercase]) is basically a type of challenge-response test used to determine whether an internet user is human. CAPTCHAs are often used to stop bots and other automated programs from using blogs, contact forms, and other internet forms to send spam, gain higher search engine rankings, take part in online polls, etc. A CAPTCHA usually comes in the form of an image of slightly distorted alphanumeric characters, like these:

A human can usually read the characters in the image without too much difficulty. A bot program is able to recognize that the content contains an image , but it has no idea what the image is, or what characters are displayed on it.

To accommodate the visually-impaired, some CAPTCHAs come in the form of an audio in which the human listens to a series of letters or short words and types what he hears to prove he is not a bot.

Integration

The CAPTCHA code is integrated with a form on your web site, and you’re done! CAPTCHAs are by definition fully automated — once you implement a CAPTCHA solution, you can pretty much sit back and watch it work.

Requirements

Examples

See our Contact page for an example of a working CAPTCHA. A different version of a working CAPTCHA can be seen on the PA Internet Marketing contact form.