I’M NOT A ROBOT!!! How a CAPTCHA Evaluates that

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Digital SecurityI’M NOT A ROBOT!!! How a CAPTCHA Evaluates that

CAPTCHA is an abbreviation for “Completely Automated Public Turing test to tell Computers and Humans Apart”. CAPTCHAs are the tools used to differentiate between humans and bots with the help of different tests.

CAPTCHAs are not intended to stop users from browsing, but are made to filter out any fake traffic generated on the site by bots or other automated means. Only humans are smart enough to pass through the CAPTCHA code.



Why does CAPTCHA appear in the first place?

The term CAPTCHA was introduced in 2000 at Carnegie Mellon University. The reason behind the invention of CAPTCHA was briefly explained by Luis von Ahn, a Carnegie Mellon professor who was part of the CAPTCHA team, who said: 

“Anybody can write a program to sign up for millions of accounts, and the idea was to prevent that.”

Mainly, the idea is there to protect the website you created and visit on a daily basis from unwanted traffic, spam, and abuse. Ticketmaster is an excellent example: the site uses CAPTCHA to prevent bots from buying hundreds of tickets before a concert sells out, and reselling them for higher prices.

However in recent years, as you might have realized, the CAPTCHAs are getting difficult by the day due to the sophistication of bots. Google now owns the software and generates new versions of CAPTCHA every now and then, also due to the sophistication of bots. 

As explained by Google in their security blog, a CAPTCHA can be triggered by automated processes sometimes caused by worms, proxy search traffic going through infected computers or routers, or from some SEO ranking tools.

If you are using PureVPN’s shared IP, it means that you are sharing your IP with many other PureVPN users. In that case, you are not the only one sending queries to Google – many other users of PureVPN are also doing the same thing at the same time.

To Google, it looks like a ton of searches coming from the same computer at the same time, like spam. That is why Google asks you to fill out the CAPTCHA every now and then, just to make sure you are a human and not a computer program.

Now the question is: why do we see different types of CAPTCHAs and how are they different from each other? 

What are the different types of CAPTCHAs?

Math Problems

For these types of CAPTCHAs, a simple math problem has been given to the user to solve. It might sound strange, but these math problem CAPTCHAs are difficult for bots to solve and thus this type of CAPTCHA is effective.

math problem

Word Problems

Another type of CAPTCHA includes a word problem where a user has to decipher the text appearing on the screen. The test might ask users to type different letters appearing in different sequences in the text box to pass the CAPTCHA.

As bots are becoming intelligent day by day, this CAPTCHA is easy for them to solve, which poses an issue for these particular CAPTCHAs.

CAPTCHA question

Time-Based CAPTCHA

This test records time the user takes to fill out a form. Bots tend to fill the form almost instantaneously. Humans, on the other hand, take an ample amount of time to fill out the form that helps easily to determine whether the user is robot or human.

Confident CAPTCHA

The most common and popular type of CAPTCHA is a test based on images. Users need to click on the images by following the instructions given by the CAPTCHA. For example, “Click on the image that has shoes.”

Although this CAPTCHA has 96% success rate, users find them frustrating because if the task is not performed correctly the first time, they will have to go through the same process again with a different image.

CAPTCHA question image


This CAPTCHA type was introduced by Google in 2014. The test is very simple to take; the user only needs to click on the box that says “I’m not a robot” and then the CAPTCHA calculates and determines whether the user is bot or a human, based on the part of the box they clicked. Bots are usually methodical and click on the center of the box, so it makes it easy to differentiate between humans and bots.


CAPTCHA v3 (Invisible CAPTCHA)

Like its name, this CAPTCHA type is not visible to the end user and all the work done silently in the background to differentiate between bots and humans. It is the upgraded version of CAPTCHA v2. How does it work? We’re not entirely sure; it has NOT yet been explained by Google (probably to make sure bots never get around it). But we do know that some activity is conducted on site, and on the basis of user history, a score is assigned to the user. If the assigned score is from 0 to 0.5 it’s considered as a bot, but from 0.5 to 1.0 it’s considered human.

Final Thoughts

As technology is evolving and progressing day by day, it seems like there is no perfect solution. For every newer version of CAPTCHA, there is a new generation and better version of bots. But does it mean that CAPTCHA is no longer useful and simply a frustrating tool that hurts the user experience? No, the idea is still alive. As technology and AI algorithms continue to evolve, we might be able to see a better and newer version of CAPTCHA that works better than its previous iterations. Until then, we have to work with the best solutions that are available to us.

What do you think is the future of CAPTCHA? Share your thoughts in the comments.

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