noun

CAPTCHA

KAP-chuh

CAPTCHA (noun) means a small test on a website meant to tell a real person apart from an automated programme, such as reading distorted letters, picking out images that contain a certain object, or ticking a box that quietly measures how the visitor behaves. Example: “I failed the CAPTCHA twice before it accepted that I could see a bicycle.”

noun

computing A small test on a website meant to tell a real person apart from an automated programme, such as reading distorted letters, picking out images that contain a certain object, or ticking a box that quietly measures how the visitor behaves.

"I failed the CAPTCHA twice before it accepted that I could see a bicycle."

"They added a CAPTCHA to the sign-up form after thousands of fake accounts appeared overnight."

verb

informal, computing To place such a test in front of a page, form or action.

"We captcha'd the contact form because it was being flooded with spam."

How to Use CAPTCHA

Learner’s notes

In plain EnglishThe little test on a website that checks you are a person and not a machine.

When to use it

Usually written in capitals as CAPTCHA, though lower-case captcha is common in casual writing. The verb use is informal.

Memory tip

It takes the indefinite article 'a', matching the spoken sound: a CAPTCHA.

Trace the full origin ↓

Easily confused with

reCAPTCHA bot → Turing test rate limiting

Common pairings

solve a CAPTCHA fail a CAPTCHA CAPTCHA challenge image CAPTCHA invisible CAPTCHA

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Fill the Gap

Can you complete this real example?

I failed the _____ twice before it accepted that I could see a bicycle.

Etymology

An acronym of completely automated public Turing test to tell computers and humans apart.

Origin: English

Synonyms

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human verification bot check challenge-response test human test gate challenge

Related Words

man test door challenge appeal blame contest gate

Frequently Asked Questions

What is the difference between a CAPTCHA and reCAPTCHA?

CAPTCHA is the general name for any test designed to separate people from automated programmes. reCAPTCHA is one particular branded service that provides such tests, so every reCAPTCHA is a CAPTCHA, but many CAPTCHAs come from other providers or are built in-house.

Why do CAPTCHAs ask about traffic lights and bicycles?

Picking objects out of photographs is a task people handle easily and automated scripts historically handled poorly, so it works as a rough divider. The same answers can also be used as labelled training data for image-recognition systems.

Why does a CAPTCHA sometimes pass with just a tick box?

Newer tests do not rely only on the puzzle. They look at signals such as mouse movement, timing and browser characteristics, and if those look consistent with a person, the visible challenge is reduced to a single tick.

Example Sentences

Real-world examples showing CAPTCHA in context, drawn from published sources. Any opinions expressed are those of the original source and do not reflect the views of FreeDict.com.

The CAPTCHA has quietly become a test people fail more often than machines do.

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