CAPTCHA
CAPTCHA is a protective test designed to distinguish a real user from a computer program (bot). The word stands for completely automated public Turing test to tell computers and humans apart. It prevents spam, data theft and excessive load on servers.
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What is CAPTCHA in simple words
CAPTCHA is a special test that websites use to determine who is in front of them — a live person or a computer bot. It is an automated test that helps distinguish real users from automatic programs.
You encounter CAPTCHA every day: when you register on a website, buy tickets, leave a comment or simply refresh the page too often. The site asks you to select all the pictures with traffic lights, enter distorted letters or simply tick the “I am not a robot” box.
The name CAPTCHA is an abbreviation of Completely Automated Public Turing test to tell Computers and Humans Apart. The test is based on tasks that are easy for a human, but very difficult for artificial intelligence or an algorithm.
CAPTCHA protects websites from spam, fraud and overloads. Without it, bots could create millions of fake accounts, leave tons of spam in comments or buy up all the concert tickets in a split second. Read about how CAPTCHA is related to website security in the article Information security.
Main types of CAPTCHA
1. Text CAPTCHA
The user needs to recognize and enter characters that are heavily distorted or crossed out with lines. This is the classic and oldest type of CAPTCHA. It is used less often now, as modern neural networks have learned to bypass it.
2. Interactive CAPTCHA (reCAPTCHA)
The most popular modern type. The user simply ticks the “I am not a robot” box. The system analyzes cursor movement, clicks and browser history. If the algorithm doubts, an additional task appears — select all the pictures with certain objects (traffic lights, pedestrian crossings, buses).
3. Audio CAPTCHA
Listening to a set of digits or words and entering them into a text field. It is used for people with visual impairments, and also as an alternative if the visual CAPTCHA does not load.
4. Invisible CAPTCHA
Works in the background, analyzing user behavior. If the system does not see suspicious activity, the verification passes unnoticed. If there are doubts, a standard task appears.
5. Slider CAPTCHA and puzzles
The user needs to assemble a picture from pieces or move the slider to the end. Such CAPTCHAs are convenient on mobile devices and are often used in VK ID and other Russian services.
Why CAPTCHA appears
The system requests confirmation if the algorithms notice suspicious activity:
- Too frequent requests from one IP address: You refresh pages or submit forms too quickly.
- Use of a VPN or proxy: Public IP addresses often raise suspicions in security systems.
- Unusual behavior: Mouse movements that look robotic, or too fast text entry.
- Unusual activity time: Requests at off-hours or from an unusual geolocation.
Why it is not possible to pass the CAPTCHA
If the CAPTCHA does not pass, the problem is usually in the browser or network settings:
- JavaScript is disabled: Many CAPTCHAs require JavaScript to work.
- An ad blocker is active: Extensions like AdBlock can block CAPTCHA scripts.
- A VPN or proxy is active: The site may consider your IP address suspicious.
- Cookies are disabled: Some CAPTCHAs use cookies for verification.
Read about how to protect your devices in the article Antivirus software.
Frequently asked questions
What is CAPTCHA in simple words?
CAPTCHA is a test that checks that you are a human, not a bot. Websites use CAPTCHA to protect against spam, fake activity and automatic attacks. You may be asked to enter distorted letters, select pictures with certain objects or simply tick the “I am not a robot” box. Read about website protection in the article Information security.
What types of CAPTCHA are there?
The main types: text (entering distorted characters), interactive (the “I am not a robot” box plus selecting pictures), audio (listening and entering digits), invisible (works in the background) and slider CAPTCHA (assembling a puzzle or moving the slider). The most popular type is reCAPTCHA from Google. Read about protection technologies in the article Antivirus software.
Why do you need CAPTCHA?
CAPTCHA protects websites from bots and automatic programs. Without CAPTCHA, attackers could create millions of fake accounts, leave spam in comments, buy up all the tickets to events or hack accounts by brute-forcing passwords. CAPTCHA also protects servers from excessive load.
Why can't I pass the CAPTCHA?
The reasons can be different: you have a VPN or proxy on, an ad blocker (AdBlock) is active, JavaScript is disabled, cookies are turned off or you send requests too quickly. Try disabling the VPN and blockers, clearing the browser cache and reloading the page. Read about browser settings in the article Incognito mode.
Can you bypass CAPTCHA?
Technically yes, there are CAPTCHA solving services that use real people or neural networks. However, using such services violates the rules of many websites and can lead to a block, and in some cases to liability under Art. 272 of the Criminal Code of the Russian Federation (illegal access to computer information). For ordinary users, the best way is to correctly pass the CAPTCHA with clean browser settings.
Is Google CAPTCHA safe?
Yes, reCAPTCHA from Google is a legitimate and safe service. However, in Russia using reCAPTCHA is complicated — the service may not load due to blocks or send data to foreign servers, which violates the 152-FZ on data localization. Russian websites are increasingly switching to domestic analogues (Yandex SmartCaptcha).
How does invisible CAPTCHA work?
Invisible CAPTCHA works in the background, requiring no action from the user. The system analyzes user behavior: mouse movements, typing speed, browser history, time on the page. If the behavior looks “human”, the verification passes unnoticed. If there are suspicions, a standard task appears. Read about protection from tracking in the article Digital footprint.
Other terms in «Information Security»
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CAPTCHA
CAPTCHA is a protective test designed to distinguish a real user from a computer program (bot). The word stands for completely automated public Turing test to tell computers and humans apart. It prevents spam, data theft and excessive load on servers.
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