Chapter 5. Implementing CAPTCHA using Draggable and Droppable

In the previous chapter, we created a reddit news reader that was a bit complex from a coding point of view. To compensate for this, we will reduce our pace a bit in this chapter and develop various implementations of CAPTCHA.

CAPTCHA (short for Completely Automated Public Turing test to tell Computers and Humans Apart) is a form of test where web forms present questions to users that are supposed to be solved by humans only.

Imagine a simple registration form of a website. If you know all the fields present in the page, you can write a script to register as many times as you can.

Now, suppose a CAPTCHA challenge is placed in the registration form, where the user is shown 10 different colors and is asked to select a random color. A regular bot will not be able to do so and hence the registration will fail.

Note

The main purpose of CAPTCHAs is to present such tests that only human users could pass. Any scripts or bots should...