Example: "Online forms may include captchas to prevent automated programs from submitting data."
A captcha is a challenge-response test that determines whether a user is human or an automated bot. A typical captcha includes an image of distorted text and a form field for the user to enter the text. Captchas are commonly found at the end of website forms, and must be filled out in order for the form to be submitted. By requiring users to decipher and enter the captcha text, webmasters can prevent automated programs from sending spam or other unwanted data through online forms.