What Do You Know About A CAPTCHA and How Does It Work?

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Written By Nidhi Sharma

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How does a visitor see a box-shaped icon with letters?

To prove that the receiver is real, the user must retype the information. This is called CAPTCHA. It stands for Completely Automated Public Turing Test to Tell Computers and Humans Apart.

This blog post will discuss the purpose of CAPTCHA and its working methods.

What is CAPTCHA and why is it important?

A CAPTCHA is usually a picture of several messed-up characters against a blurred background. Many CAPTCHA challenges require people to identify pictures and do simple math problems. They also have to respond to an audio clip or tap a box that says "I'm no robot."

CAPTCHA is the Key Purpose

This algorithm is accessible to all by using the letter "P" in the CAPTCHA.

Around 1996, the assessment was done in different ways. It was given its unique name by Carnegie Mellon University researchers in 2020. This algorithm generates random sequences of numbers or letters in an image. Therefore, if you bust it, the CAPTCHA won't be affected. Because people and computers think differently about character strings, the framework works.

CAPTCHA offers protection against commercial spamming. This is a practice that allows fraudsters to use comments on websites to promote their frauds. This leads to an increase in cyber-related crime, threats, and attacks.

By requiring all visitors to complete the CAPTCHA verification, admins can stop internet trolls from trying to digitize their actions. CAPTCHA technology ensures that the online content is accessible only to real humans. This is to prevent spammers and bots from registering on blogs, forums, or websites without anyone's assistance.

Because they cannot read the distorted text in the image, automated systems can't get past CAPTCHA.

What does each type of CAPTCHA do?

1. What is Traditional CAPTCHA?

The traditional CAPTCHAs are still being used on certain websites. They ask users to select letters. Bots can't figure out the text because it is mangled. Users must find the text that is messed up and then enter the correct characters in a web form to qualify.

If the text does not match, users are encouraged to try again. These types of tests are often used to verify account registrations online and online surveys. Software programs like bots will not be able to decipher the meaning of the misinterpreted letters.

A person who has mastered the art of reading and deciphering handwriting and font styles will be able to identify what they are.

Many bots can type random letters. This makes it less likely that they will be able to correctly enter the sequence and pass the test. Bots will fail, so they can't access the website or app. Humans can still use it as normal.

2. What is Google’s reCAPTCHA?

Advanced bots can use ML machine-learning to determine what these letters are. These types of CAPTCHA tests have been gradually phased out to make way for more difficult ones. Google's reCAPTCHA allows you to distinguish between humans and bots with a variety of tests.

Google's new reCAPTCHA is a free resource that can replace traditional CAPTCHAs. Google purchased the reCAPTCHA invention in 2009 from Carnegie Mellon University research teams.

ReCAPTCHA is more intelligent than regular CAPTCHA tests. Many reCAPTCHAs are similar to a CAPTCHA and require the user to enter the text that computers cannot read. ReCAPTCHA differs from other CAPTCHAs in that the text is derived from photographs of real-world objects, such as street names and old newspapers.

Over the years, Google has added many more features to reCAPTCHA. They no longer require the old method of finding pixilated text or constrained text. You can also use reCAPTCHA to evaluate:

  • Image recognition
  • Checkbox
  • Evaluation of the user's behavior in general

Google has updated reCAPTCHA versions over time: v2 and v3. To learn more about reCAPTCHA V2 Vs V3, you can visit the link above. This will help you understand what reCAPTCHA version 3 can and cannot do to protect your website's security.

This guide also explains the differences between reCAPTCHA v2 and v3, identifies the pitfalls in reCAPTCHA v3 configurations, and summarizes what a true bot protection and mitigation solution should deliver.

3. CAPTCHA Test that Searches for Images

During a CAPTCHA image recognition test, users are typically shown nine to sixteen square-shaped images. These pictures can be part of one large picture or all different.

The visitor must find images that contain certain elements, such as signs, plants, living creatures or signs. The viewer is considered correct if their answer matches the majority of other answers in the same test.

Computer systems have a hard time figuring out how to pick certain items from grainy photos. Artificial intelligence (AI) programs with high intelligence have difficulty understanding this problem, so a bot also faces the same problem. Because people are used to seeing everyday objects in many different situations, an AI program can do this easily.

4. CAPTCHA Tests with Only One Box to Test

Some CAPTCHA tests ask users to check a box next to the phrase "I'm NOT a robot" The test is not about tapping the tickbox; it's about all that happens before you click the checkbox.

The CAPTCHA test measures how the cursor moves when it gets near the tick box. Even though a person can move in a straight line there are subtle subconscious movements that make it difficult for bots.

The test will determine if the cursor's movement is random. The test might also examine the history of the computer and the cookies stored in the browser to determine if the visitor is a bot.

The assessment might not be able to determine if the visitor is real. If this happens, the assessment may add additional challenges like image recognition tests. Most users can be identified by their cursor movements, gadget history, and cookies.

5. CAPTCHAs that The User does not do Anything

CAPTCHA's newest versions can be used to check a user’s online behavior and history.

The software will usually determine if users are bots by looking at these factors, without assigning them any task. If they do not pass, they will be shown a standard CAPTCHA test. As a way to prevent bots from getting in, some websites automatically have CAPTCHAs. If a person's actions resemble those of spammers, then a test can be performed.

A test could be conducted if a user clicks on links or accesses pages at a faster rate than normal.

6. CAPTCHA Testing and AI projects

AI software is better at finding objects in grainy photos and reading difficult words. This is because thousands of people use them. The data is then input into the AI system.

Computers find it difficult to recognize letters and objects in different contexts, as reality can change so drastically.

A stoplight, for example, is red with the word "STOP" in white on an oval-shaped object.

It would be simple for a computer algorithm and computer software to determine if there is a structure or text combination like this. A stoplight in a photo could look different depending on its angle, lighting, weather, and other factors.

AI can be great at overcoming these issues with ML. A programmer can give AI software lots of information about stop signs.

They need multiple examples of photos, including pictures that have stop signs or not. They require people to help them pick them until the software has enough information for this task.

CAPTCHA is a method that allows individuals to identify messages and items. This provides enough data over time to build strong AI algorithms.

7. CAPTCHA and Turing Tests

Turing tests are used to measure the ability of a computer to behave like a human. This test was created by Alan Turing in 1950. Turing was one of the first computer scientists to create it.

If a code behaves exactly like a person during the assessment, it "passes" this test. It can't be distinguished from an individual. It doesn't really matter if answers are correct or wrong for the Turing test. What matters is how "human" the answer sounds.

A CAPTCHA, although it is sometimes called "Public Turing tests", is actually the opposite of the former. Instead of trying to determine if a device can communicate, it examines whether a "human visitor" is actually a bot.

CAPTCHA tests are required to perform a brief task that most people can do but computers struggle with. These criteria include recognizing images and text.


On websites that allow users to submit information, CAPTCHA is required. CAPTCHA is not usually required to allow users to input information from those who are already registered in their accounts.

CAPTCHA can slow down unauthenticated users such as bots who attempt to post spam messages on forums or blogs, but without having to be verified as real users.

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