Arkose Product

What is a CAPTCHA?

June 13, 20192 min Read

“CAPTCHA” is an acronym for “Completely Automated Public Turing test to tell Computers and Humans Apart”. That’s a bit of a mouthful and for those of us who don’t know what a “Turing test” is — still a bit confusing. It refers to the test proposed by Alan Turing in 1950 that attempted to determine if a computer could “think”. Turing quickly realized that the term “think”, in this context, was a bit ambiguous so he refined the focus and further elaborated: the test aimed to evaluate how well a computer could emulate or exhibit behaviour indistinguishable from that of a human user by having a human judge engage in conversation with both a human participant and a computer participant. But enough history! What are CAPTCHA’s doing today and why are they so hard?


Well, as the name CAPTCHA implies, the general principle behind the “Turing test” has been adopted into a more automated approach that is being completed almost 300,000,000 times per day. That is a LOT of testing. But why? Protection from malicious software is obviously of high importance for those responsible for online services so (unfortunately) the twisty and hard to read CAPTCHAs were initially chosen for the task. For the last few years, it’s been the only way to engage users in the “Turing test”.

However, as the sophistication of the recognition software increased, so too did the difficulty of these distorted text/image CAPTCHAs. This revealed a fundamental flaw in the traditional text/image method: the only way to make the test harder for bots was to make the text/images warped and distorted to the point where even humans could barely understand what they were being presented with.

Arkose Labs' Enforcement Challenge

We realized that for CAPTCHAs to remain a relevant and effective web security asset, they needed innovation or the problem would only get worse. Considering the necessity, annoyance and sheer volume of traditional CAPTCHAs, you can see why we’re so focused on reinvigorating the process with something that’s fun and engaging — hence, Arkose Labs was born.