An anti-spam technique that was developed to block robots from spamming a site. CAPTCHA works by asking the user to answer a question or solve a problem that computers were supposedly incapable of solving but humans were.

Types of CAPTCHA include:

  1. Asking the user to read a bit of hard to read text in an image.
  2. Asking the user to solve a math problem (such as "what is 2 + 2").
  3. Asking the user to answer a question (such as "what is the name of this site?").

Robots have gotten better at reading text in images over the years, which is why some people advocate using option 2 or 3 instead.

history | show excerpt | excerpt history