# What is a CAPTCHA? | SoftGlaze Browser glossary > A CAPTCHA tells people from bots, from distorted text to invisible risk checks. How modern captchas decide whom to challenge, and what makes a profile risky. - Canonical URL: https://browser.softglaze.com/glossary/captcha - Last updated 2026-11-09 --- [Accounts and sessions](https://browser.softglaze.com/glossary?category=accounts-and-sessions) ## CAPTCHA Also called captcha, captcha verification, hCaptcha, Cloudflare Turnstile, bot check, challenge page Definition A CAPTCHA is a challenge a website uses to tell people from automated programs, such as typing distorted text, picking images or, more and more often, passing an invisible check of the browser and its behaviour. Last updated 7 November 2026 ### How it works The name stands for “Completely Automated Public Turing test to tell Computers and Humans Apart”, coined by Luis von Ahn and colleagues in 2003. Early captchas were puzzles: distorted letters, then image grids. As software got better at puzzles, the services moved most of the work out of sight. Today’s widely used captchas, such as Google reCAPTCHA, hCaptcha and Cloudflare Turnstile, first look at the browser, the network and the way the visitor behaves, and only show a puzzle, or block, when that check is unconvincing. So a captcha is usually the visible end of a risk decision rather than a fixed gate. The same page can wave one visitor through and challenge the next. ### Why it matters when you run several accounts Frequent captchas tell you a profile looks risky to the sites it visits. The usual reasons are the network (an address with a poor reputation, on a blocklist or in a hosting range), a browser that contradicts itself (time zone, language and IP in different places), signs of automation, or behaviour that is faster and more regular than a person’s. Captchas exist to stop abuse; a profile meeting many of them is worth fixing, not forcing through. ### How SoftGlaze Browser handles it SoftGlaze Browser doesn’t promise fewer captchas. It gives you the checks that find the usual causes. Each profile has a CAPTCHA risk score out of 100 that lists the reasons, and the profile list can be sorted and filtered by it; safe fixes, such as matching the time zone, language and location to the proxy or choosing a safer WebRTC mode, apply to one profile or many. Each proxy check looks the exit address up on 3 DNS blocklists and grades it, and Leak Check scores a profile’s consistency. From version 1.0.22, SoftGlaze AI (Beta) adds a prompt, “Why does this profile get CAPTCHAs?”, that reports what to fix. The acceptable use policy sets out what is and isn’t acceptable around challenges. ### Sources 1. [CAPTCHA: Using Hard AI Problems for Security (von Ahn, Blum, Hopper and Langford, 2003)](https://www.cs.cmu.edu/~biglou/captcha_crypt.pdf) Carnegie Mellon University 2. [Cloudflare Turnstile documentation](https://developers.cloudflare.com/turnstile/) Cloudflare 3. [hCaptcha developer guide](https://docs.hcaptcha.com/) hCaptcha Outside sources were checked in November 2026. Browsers, standards and vendors' pages change, so details that depend on them are as of that month. ### Related terms - [reCAPTCHA](https://browser.softglaze.com/glossary/recaptcha) reCAPTCHA is Google's captcha service; version 2 shows the "I'm not a robot" checkbox and image challenges, and version 3 runs invisibly and returns a score from 0.0 to 1.0 that the site uses to decide what to do. - [IP reputation](https://browser.softglaze.com/glossary/ip-reputation) IP reputation is the judgement that security services and websites keep about an IP address, based on what has been seen from it before (spam, attacks, fraud, heavy automation) and on the kind of network it belongs to. - [navigator.webdriver](https://browser.softglaze.com/glossary/navigator-webdriver) navigator.webdriver is a browser property that the W3C WebDriver standard requires to be true when the browser is under automated control, so a page can tell an automated session from a person using the browser. - [Browser fingerprint](https://browser.softglaze.com/glossary/browser-fingerprint) A browser fingerprint is the combination of values a website can read from your browser and device without storing anything, such as the user agent, screen size, time zone, fonts and graphics card, which together can tell one browser from another. - [Timezone mismatch](https://browser.softglaze.com/glossary/timezone-mismatch) A timezone mismatch is when the time zone a browser reports does not fit the location of the IP address it connects from, for example a browser on London time arriving from a New York address. ### Read more on this site - [Acceptable use: automation, and solving captchas](https://browser.softglaze.com/acceptable-use#automation) - [Docs: Leak Check](https://browser.softglaze.com/docs/profiles#leak-check) - [AI prompt: why does this profile get CAPTCHAs?](https://browser.softglaze.com/docs/ai-prompts#diagnose_captcha) - [How to check if a proxy is working](https://browser.softglaze.com/blog/how-to-check-if-a-proxy-is-working) ### See it in SoftGlaze Browser Separate profiles, each with its own cookies, device values and proxy, on Windows. Try the app's screens in your browser first, or start the free trial; no card needed. [Download for Windows](https://browser.softglaze.com/download) [Try the demo](https://browser.softglaze.com/demo) [All terms](https://browser.softglaze.com/glossary)