Marcello Calbucci recently shared some details behind the design of the Sampa sign up form. Sampa is a free Web site service that requires users to register before they set up a site and saw a 10% increase in sign-ups with one change: removing CAPTCHA.

• The Sampa sign in form has been through 4 or 5 different versions
• At one point Sampa asked about 15 questions
• ampa A/B tested several sign up form scenarios over the last 2 years to determine the right combination that yields maximum conversion and retention
• CAPTCHA was used to prevent automated bots from creating hundreds of thousands of fake accounts
• Sampa removed CAPTCHA 99% of the time through a set of tests and rules
• The result: 9.2% improvement on our conversion rate