Viral Marketing is a marketing technique on the Internet that induces users or sites to pass on a marketing message to other users or sites that create a potentially exponential growth in the message's visibility and effect. Viral marketing has the tendency for messages to use "hosts" to spread themselves quickly just like a biological virus.

"Viral promotions can be in the form of video clips, advergames, interactive Flash games, brandable software, ebooks, images or text messages."

This type of marketing depends on a high pass-along rate from person to person. The overall growth snowballs very rapidly, if a large number of recipients forward something to a large number of people or friends. The overall growth quickly fizzles, if the pass-along numbers gets very low. Hotmail is the best example of successful viral marketing. Now, Microsoft has owned this company Hotmail that promotes its service and messages in every user's e-mail notes.

In creating successful viral marketing programs, the goal of marketers is to identify people with high Social Networking Potential and to create Viral Messages that have a high probability of being taken by other competitor.