Word of mouse is an electronic version of the time-tested idea of word of mouth. Numerous advertisers have jumped on the word of mouse bandwagon, using a variety of innovative techniques to get their message out to consumers, and businesses all over the world rely on word of mouse to promote good reputations. As electronic media grew in importance in the late 1990s, word of mouse became a new holy grail of marketing, with a host of books, articles, and commentaries on getting good word of mouse.

The idea behind word of mouth is that people tend to rely heavily on the opinions of friends, peers, coworkers, and neighbors. Businesses have known for centuries that a bad word of mouth reputation can be acquired very easily, and it is very difficult to get rid of. All a business needs is one person who complains about their service to a friend, and a bad reputation can snowball. Conversely, people who praise a business to friends can create a good word of mouth reputation.

In the rise of the electronic era, the concept of word of mouth began to be translated into a new medium, and the idea of “word of mouse” started to arise. Thanks to the instantaneous nature of electronic communications, word of mouse can spread very rapidly, and numerous forums have enabled the transmission of ideas in an increasing number of ways. Word of mouse can be passed along from person to person in the form of electronic mail, but it can also manifest in a number of other locations.

Word of mouse can be built up on review sites, which allow users to post reviews and commentary on businesses, and it can also be generated on forums, chatrooms, and social networking sites. Social networking sites are regarded by many advertisers as a very fruitful arena for generating word of mouse, with many advertisers creating profiles on such sites and engaging with the community to build up word of mouse.

Just like word of mouth, word of mouse is built on a solid reputation, and carefully maintained. Many businesses actively work to promote a specific branding and image, so that consumers visualize that particular business when they need something, whether it's a soft drink or accounting services. Word of mouse is, in a sense, an amplified form of word of mouth, because information exchange is so prolific in the electronic medium, and thanks to archiving, it can be even more challenging for businesses to overcome a bad reputation.