A CAPTCHA, which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart,” is a security feature used on websites and online services to distinguish between human users and automated bots or computer programs.

The primary purpose of a CAPTCHA is to prevent automated scripts and bots from abusing or spamming a website’s services. CAPTCHAs typically present users with challenges that are relatively easy for humans to solve but difficult for automated programs to complete. These challenges can take various forms, but some common examples include:

• Image Recognition: Users may be asked to identify and select certain objects within a set of images, such as identifying all the pictures with traffic lights or crosswalks.
• Text-Based CAPTCHAs: Users are often presented with distorted or partially obscured characters and asked to type in the text they see. This is a widely recognized form of CAPTCHA, where you might need to prove you’re not a robot by solving a puzzle like “Type the characters you see in the image.”
• Checkbox CAPTCHAs: Sometimes, users simply need to click a checkbox indicating that they are not a robot. This can be combined with other security mechanisms in the background to determine if further verification is needed.
• Puzzle Solving: Users may be required to solve puzzles or simple math problems to prove their humanity.

CAPTCHAs help protect websites from automated attacks, such as spam submissions in contact forms, brute-force login attempts, or data scraping. They are used to ensure a better user experience by reducing unwanted or harmful automated interactions while allowing genuine human users to access and use online services.

In recent years, CAPTCHAs have evolved to be more user-friendly, with newer methods often requiring only a single click or checkbox confirmation for most users, while more challenging puzzles may be presented to suspicious or potentially automated visitors.