Google Inc. has launched an online-publishing service that is a potential competitor to Wikipedia.

Google on Wednesday took the wrappings off its previously announced publishing-and-reference service called Knol, which allows users to write articles on specific topics and to make money from them.

By trying to provide such content, the service is likely to compete with online encyclopedia Wikipedia, whose articles tend to rank highly in Google search results.

Knol, which stands for unit of knowledge, allows internet users to write articles on their own areas of expertise.

The world’s largest search engine is hoping that “knols” will be written on every conceivable topic ranging from gardening and pottery to Byzantine art and neo-classical literature.

The free service will inevitably draw comparisons with Wikipedia but Google says it differs from it in many ways.

Unlike Wikipedia, which allows visitors to edit its pages, people will not be able to make changes or contribute to a person’s knol without their permission.

Knols written on the same subject will also remain separate and compete for the attention of visitors, who will be able to give online feedback. Pictures of authors will also be displayed on their knol web pages.

Udi Manber, Google’s vice president of engineering, said: “We believe that knowing who wrote what will significantly help users make better use of web content.

“Books have authors’ names right on the cover, news articles have bylines, scientific articles always have authors; but somehow the web evolved without a strong standard to keep authors names highlighted.”

Contributors will be able to make money from the service by allowing adverts which relate to their articles to appear on their pages.

Juergen Galler, Google’s director of product management said: “The internet is huge, but still a lot of expert knowledge remains untapped.”

“Knol provides a way for people to share their expertise with others – and get credit for their contribution.”

The service is part of a growing drive by Google to expand beyond simple search and into other areas such as desk top publishing and mobile phones.

But taking on Wikipedia is no mean feat. With 116 million global users a month – a third of the internet population – it consistently ranks among the most visited websites in the world.