Catching Up with CAPTCHAs


Tired of wondering whether to select the box with that one tiny part that kind of looks like a car bonnet when asked to pick all the pictures having cars in the CAPTCHA grid? There is no doubt that CAPTCHAs have annoyed us, especially when they pop up during last-minute submissions of forms or bookings, leaving us with the question: is this really necessary? Read on to find the answer in this article.

In order to understand this, let’s talk about the Turing test. A Turing test is nothing but a simple test that determines the ability of a computer or a bot to act human. The term CAPTCHA itself stands for Completely Automated Public Turing Test. A CAPTCHA is just an automated Turing test to differentiate between a spam robot and a human by giving tasks that essentially make sense and could be accomplished only by the human mind.

Credits: MadeInAbyss

It all started in 1993 with guessing floating stretched alphabets or numbers and recognizing patterns in images which were believed to be deciphered only by the human mind and hard to read for computers. In 2008, it was thought that why not direct this energy which was being wasted figuring out meaningless texts to figuring out archival texts and transcripts which couldn’t be scanned by computers. Thus reCAPTCHA was introduced which scanned such texts and left them for the users to decode leading to about 950 million people who contributed to this digitization. However, with the development in AI, by 2014 it was found that these spambots could scan through the texts and numbers on the images with 99% accuracy. This is when Google introduced a simple ‘I am not a robot’ check-box. They scan the user activity on the page such as mouse movement, time taken to go through, etc. before clicking on the check-box to figure out if the user patterns are humane. If not convinced, Google will give further tasks such as selecting correct images from a picture grid. Google also used reCAPTCHA to improve its Map features by using pictures of streets and signs in these grids.

Do we really need this? Yes. This helps avoid spams in cases such as voting, surveys, bookings, junk mail, registrations, etc. which could be tampered with by the means of bots. Fake ticket reservations in the railways or concerts are done within seconds with the help of bots, which are then sold in black. Same goes for fake polls and surveys. CAPTCHAs help improve the authenticity of any data received by weeding out the spambots.

With an everyday development in the AI domain, it is possible that the bots and hackers can catch up on the latest CAPTCHAs and we might need a newer version of these, but for now, we shall keep checking boxes and looking out for zebra crossings.


  1. What is Captcha? — Panda Security
  2. How CAPTCHAs Work | What Does CAPTCHA Mean? | Cloudflare
  3. The Evolving CAPTCHA — Enlightened Digital (

About the Author: Apurva Mali is a second year Computer Engineering student at RAIT.