Types of CAPTCHA

Types of CAPTCHA

By far the most common type of captcha involves the use of letters that are arranged randomly and are distorted in some way with various background colours. These are the ones that you will most likely have seen when signing up for a web mail account.

An example of the use of these can be seen when you are signing up for a Hotmail...

or Yahoo! web mail account.

Another example is the contact form on our website http://www.interspire.com/contact/.

Other alternatives do exist. Audio CAPTCHA's for the visually impaired are probably the second most common type of CAPTCHA. There are also other CAPTCHA's that require you to solve a problem that should be easy for a person but very hard for a computer to solve such as choosing which item in a list is not a bird for example but the problem with this is that you need to have a large number of questions before it really becomes effective.