Technology
How does a CAPTCHA work?
A CAPTCHA works by giving a quick challenge that's easy for humans but hard for bots, to keep automated programs out. Tasks like reading distorted text or picking images test for human perception that software has historically struggled to match.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how a CAPTCHA works.
Step by step
- 1It's a test to tell humans and bots apart.
- 2Classic versions show distorted text or image-selection puzzles.
- 3Humans solve them easily; simple bots can't.
- 4Modern ones analyze behavior (like mouse movement) invisibly.
- 5As AI improves, CAPTCHAs keep getting harder to design.
Frequently asked questions
- What does CAPTCHA stand for?
- 'Completely Automated Public Turing test to tell Computers and Humans Apart' — a test only a human should pass easily.
- Why do websites use CAPTCHAs?
- To block bots from spamming forms, creating fake accounts, or scraping data, while letting real people through.
- Why are CAPTCHAs getting harder?
- As AI gets better at reading text and images, puzzles must get trickier — which is why many now quietly analyze your behavior instead.