A type of challenge–response test used in computing to determine whether or not the user is human. – Wikipedia
Relevance in CRO
The additional UI bit at the bottom of a form that you have to complete to prove that you’re human. Captchas were designed and developed as a measure to combat automated spam on form submissions that was incentivized by disingenuous behavior; examples including things like bulk submissions to increase odds of winning a contest, filling up an inbox with junk, mass account signups, review stuffing, etc.
Captchas are a classic example of a business solution that creates a user problem. They’re a low-cost solution to a difficult technical problem (spam detection), but offload the burden of responsibility to the user. Using a Captcha essentially says “I don’t trust you” to an actual human user; deliberately creating unnecessary friction and doubt. Further, they can be an accessibility issue for visually impaired or otherwise disabled users. Some alternative solving methods have been developed such as audio, image recognition, and mathematical equations, but it’s generally insufficient.
Captchas not all that difficult to circumvent nowadays. Machine learning has been developed to crack them. There are paid outsourcing services available for bulk solving them. Also, a lot of Captchas are actually disguised machine-learning trainers; again offloading a business problem to the user. Early versions of reCaptcha with the squiggly words were used for refining Optical Character Recognition algorithms. Same thing for all of those “select the squares with stop signs”; training Google’s environmental recognition AI. Don’t use Captchas.
- Should you use Captcha on your Web Forms? – Zuko
- Having a Captcha is Killing Your Conversion Rate – Moz
- AB Testing Results are Half-Filled with Losers, and That’s a Good Thing – Conversion Sciences