What is Image Verification ( Captcha )?

Image verification is a security test to determine whether or not the user is human. This will ensure that only human visitors will actually submit the form, not spamming bots that browse the web from site to site and submit spam where they can. It is well known that programmers can build programs for many jobs, including visiting a large amount of sites on the Internet by following links from page to page and collecting emails listed on websites, submitting contact forms, or even trying to break passwords by trying to login over and over again with computer generated passwords.

Fortunately, it is impossible for a non-human ( i.e. a computer program ) to extract a word or a combination of letters and numbers from an image, if the letters and numbers are not all of the same size and in a similar font. This is why the image verification security method ensures that only humans actually can submit a form.