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How a reCAPTCHA Works When You Click "I'm Not A Robot"

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By Brennan Forrest - - 5 Mins Read
reCAPTCHA checkbox on a website
reCAPTCHA checkbox | lilgrapher / Shutterstock

Have you ever wondered what really happens behind the scenes when you encounter an "I'm not a robot" checkbox while browsing online?

This checkbox is part of the reCAPTCHA system, which is designed to protect websites from automated programs.

Let's look at how reCAPTCHA works and see how it has changed over time.

Understanding reCAPTCHA

The CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart), also known as the "I'm not a robot" checkbox, is utilized by numerous websites to verify that the user interacting with the site is indeed a human.

One of the most widely used CAPTCHAs available on the Internet is reCAPTCHA, which was developed by Google.

How reCAPTCHA Works

When the "I'm not a robot" checkbox is clicked, your browser sends various pieces of information to Google's servers for analysis.

This information includes your cursor movements (which tend to be slightly random for humans), browsing history, and cookies stored on your device.

Google's advanced programs then analyze this information to determine whether you are likely to be a real human user.

If the score is high enough, the website lets you in without any more interruptions.

Clicking the checkbox gives Google permission to check how you behave online to determine whether you're real.

Can Computers Solve CAPTCHAs Better Than People?

Interestingly, recent research shows that computer programs can often solve CAPTCHAs more accurately than people.

A study at the University of California found that AI programs had a 99.8% accuracy rate with CAPTCHAs, much better than those with human participants.

This finding shows how CAPTCHA systems like reCAPTCHA are becoming more complicated to keep up with advanced computer programs.

Evolution of reCAPTCHA

Moving Away from Traditional CAPTCHAs.

Artificial intelligence robot figure in programming language background
Photo | Unsplash

CAPTCHAs that use old-style methods, such as squiggly text or picture puzzles, were not very successful in preventing advanced computer programs that use pattern recognition.

To address this, reCAPTCHA was made with harder challenges that are easier for people but harder for bots.

Different Versions of reCAPTCHA

  • reCAPTCHA v1: Showed twisted text from scanned books or articles. But it was not great at stopping advanced bots.
  • reCAPTCHA v2: Had interactive challenges like picking out pictures or using a checkbox ("I'm not a robot"). This version aimed to be both good at stopping bots and easy for users.
  • reCAPTCHA v3: Looked at user behavior quietly to give a risk score. This version doesn't bother real users much but spots bot well.

Types of reCAPTCHA Tests

  • Picture reCAPTCHA

This test asks users to pick out specific objects in a grid of pictures, like choosing all squares with crosswalks or fire hydrants. It's hard for bots to copy how people do this.

  • Checkbox reCAPTCHA

An easier test involves users clicking a box to say they're not robots. However, this test also looks at how the cursor moves and other browsing data to check if you're human.

Pros and Cons of reCAPTCHA


  • Free: Any website owner can use it without paying.
  • Security: Stops spam, tricks, and abuse well.
  • Choices: Comes in different styles for different people.
  • Saves Time: Keeps fake users out to save time for real visitors.
  • Changes: Gets better at stopping new bot tricks with computer learning.


  • User Experience: This breaks the flow for users and can make them unhappy.
  • Effectiveness: Some old versions are still bad at stopping clever bots.

Installing reCAPTCHA on Your Website

To include reCAPTCHA on your website, you will need to obtain unique keys from Google and input them into your website's forms.

This process can be accomplished manually using HTML or PHP, or simpler methods can be utilized with WordPress plugins.

Website owners can maintain the security of their sites from automated threats while guaranteeing user satisfaction with the use of reCAPTCHA.

In spite of the consistent technological advancements, reCAPTCHA remains an essential tool in ensuring the safety and reliability of online content.


As the internet changes, so do the challenges from sneaky bots. reCAPTCHA keeps changing, too, and it uses smart programs and computer learning to stay ahead.

Also, many websites use reCAPTCHA to stop attacks. From small blogs to big companies, sites around the world trust reCAPTCHA to keep things safe and trusted.