What is CAPTCHA?

CAPTCHA

CAPTCHA stands for Completely Automated Public Turing Test to tell Computers and Humans Apart. These tests are used to prevent automated programs, like web crawlers or bots, from accessing websites.

CAPTCHAs achieve their goals by having users complete tests that are meant to distinguish between humans and programs. Common CAPTCHA tests include having the user write text from an image or audio file into the answer field, selecting images that contain a particular object, and simply clicking on a checkbox.

Uses

Several uses for CAPTCHA-based security methods are:

• Bots can be prevented from spamming comment sections.
• Automated programs can be stopped from registering accounts on websites.
• CAPTCHAs can be used to maintain the integrity of online polls, surveys, and other forms.
• Web crawlers often look for email addresses over the web. These addresses can be hidden and protected from spam by hiding them behind a CAPTCHA.
• A CAPTCHA can also be used to prevent Denial of Service attacks, where servers are overloaded with requests by bots.