Why do websites use CAPTCHA systems?

On many websites, it is required to solve a so-called CAPTCHA when registering, sending a message or submitting a comment. Usually, CAPTCHAs are some digits or letters that are presented, for example on an image, and have to be entered. Only with a correct input, it is possible to proceed and you can continue with the registration or you can submit your comment.

CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. In other words: A CAPTCHA is nothing more than a test to determine whether it is a computer or a human being trying to make the entry.

But why is this necessary?

Perhaps you might think that it should not be of any interest for the operators of a website, whether an input is coming from a human or a computer. Usually, it should not be - but the automated systems have become to much.

However, today a great number of automated computer programs called bots all over the world are trying to automatically access to web pages and filling out their forms. The underlying intention may be different: spreading of advertising in comments on a blog, automated access to email accounts in order to send spam mails, registrations on social networks like Facebook to spy user data - just to name a few things.

Our websites including askingbox.com are also affected by this vexation, even if a promotional comment that was entered via the contact form would never be published anyway. But, however, a big problem is that serious questions and requests can quickly get lost in thousands of spam mails if you do not try to stem this problem.

Web site operators try to defend themselves

For this reason, more and more operators of Internet sites are using CAPTCHAs. The idea is that an automated computer fails with solving the CAPTCHA and so, it can not continue. So, the CAPTCHA should distinguish between humans and computers.

Some of these CAPTCHAs are quite difficult to solve even for humans. The letters are distorted, the colors lacking in contrast, people with a visual impairment are partly never able to solve the puzzles at all (problem for accessibility). The reason for this is that a race between the bots and the creators of CAPTCHAs has already begun, as more and more automated bots are able to solve some CAPTCHAs. To prevent this automatic solution, the CAPTCHAs are becoming increasingly difficult.

We use a compromise on our pages and do not make it so hard. Sometimes, we are using automated methods so that we only show the CAPTCHA in critical cases to ensure that no user becomes unnecessarily frustrated. Of course, we take it into account that sometimes, a bot comes through with a message, why we have always a second level of human review of the input. But that is quite manageable, as it is still limited.