captcha

noun

capt·​cha ˈkap-chə 

variants or CAPTCHA

: a test to prevent spamming software from accessing a website by requiring visitors to the site to solve a simple puzzle (typically by reading and transcribing a series of numbers or letters from a distorted image) in order to gain access

The point of the CAPTCHA is that reading those swirly letters is something that computers aren't very good at. If you can read them, you're probably not a piece of software run by a spammer.

—Lev Grossman

Examples of captcha in a Sentence

Recent Examples on the Web

Recipients are also asked to complete a CAPTCHA challenge in order to appear legitimate, before they're directed to a fake iCloud login page. —Megan Cerullo, CBS News, 8 July 2024

The captcha may also make the page look more convincing to targets. —Dan Goodin, Ars Technica, 18 Apr. 2024

Already, some services such as Roblox use very difficult CAPTCHAs, likely to keep ahead of similar improvements in computer vision. —Benj Edwards, Ars Technica, 18 July 2023

The redirections lead to sites pushing fake tech support, fraudulent lottery wins, and push notification scams, the latter of which trick visitors into subscribing to push notifications by displaying fake captcha dialogs. —Kevin Purdy, Ars Technica, 9 Oct. 2023

Word History

Etymology

Completely Automatic Public Turing test to tell Computers and Humans Apart (with deliberate pun on capture entry 1)

First Known Use

2001, in the meaning defined above