# How do web page verification codes work?

**URL:** <https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070>\
**Category:** Factual Questions\
**Created:** [August 2, 2007, 1:45am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070 "2007-08-02T01:45:06Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\
**Post date:** [August 2, 2007, 1:45am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070/1 "2007-08-02T01:45:06Z")

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These are those words that are distorted by lines or squiggles on web pages. You are asked to type out the word correctly on your keyboard to enter a secure internet site. Usually it is easy to see what the word is amidst all the other lines but sometimes the word gets lost in the mess. It has something to do with entering a secure site but all I can figure is that it prevents people with bad vision from accessing certain web pages.  
How do these things work?

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [August 2, 2007, 1:51am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070/2 "2007-08-02T01:51:59Z")

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They are intended to prevent automated systems from accessing whatever the system is protecting. It’s called CAPTCHA, and works on the principle that human pattern recognition is vastly superior to any OCR system yet designed; we can pick out letters and numbers on a “noisy” background easily, whereas computer programs cannot.

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**Author:** ![ZipperJJ](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zipperjj/32/211_2.png) [@ZipperJJ](https://boards.straightdope.com/u/ZipperJJ)\
**Post date:** [August 2, 2007, 1:52am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070/3 "2007-08-02T01:52:56Z")

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It’s called a captcha. It’s not about entering a secure site. It’s for keeping bots from spamming web-based forms.

> **[CAPTCHA](https://en.wikipedia.org/wiki/Captcha)**
>
> A CAPTCHA (/ˈkæp.tʃə/ KAP-chə) is a type of challenge–response test used in computing to determine whether the user is human in order to deter bot attacks and spam.
> The term was coined in 2003 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford. It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart." A historically common type of CAPTCHA (displayed as Version 1.0\[clarification needed\]) was first invented in 1997 by two group...

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**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\
**Post date:** [August 2, 2007, 2:59am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070/4 "2007-08-02T02:59:28Z")

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Until I read that wiki article a few months ago, I had no idea that CAPTCHA was an acronym. 🙂

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**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\
**Post date:** [August 2, 2007, 4:12am UTC](https://boards.straightdope.com/t/how-do-web-page-verification-codes-work/414070/5 "2007-08-02T04:12:24Z")

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[QUOTE=Sunspace]  
Until I read that wiki article a few months ago, I had no idea that CAPTCHA was an acronym. 🙂  
[/QUOTE]

Captcha ya!