Definition
Plain language
The little puzzle a website shows you to prove you're not a robot.
As stated in the literature
A challenge-response test designed to distinguish humans from automated agents, increasingly a failure mode for web-browsing AI agents.
Also called: CAPTCHA
Why it matters: Captchas are increasingly the bottleneck that determines whether a browser agent can actually finish a real task on the web.
For example, an AI shopping agent might get all the way to checkout and then be stopped by a 'click all images with bicycles' captcha.
Heard on the show
“Forty-one percent of them — over two thousand tasks — were failures because the website served a captcha every single time and the teacher couldn't get past it.”Episode 047 — When Agent Benchmarks Lie: The Harness Problem in Open-Source AI