An online encyclopedia is an encyclopedia accessible through the internet. The idea to build a free encyclopedia using the Internet can be traced at least to the 1994 Interpedia proposal; it was planned as an encyclopedia on the Internet to which everyone could contribute materials. The project never left the planning stage and was overtaken by a key branch of old printed encyclopedias.
Another related branch of activity is the creation of new, free contents on a volunteer basis. In 1991, the participants of the Usenet newsgroup alt.fan.douglas-adams started a project to produce a real version of The Hitchhiker's Guide to the Galaxy, a fictional encyclopedia used in the works of Douglas Adams. It became known as Project Galactic Guide. Although it originally aimed to contain only real, factual articles, policy was changed to allow and encourage semi-real and unreal articles as well. Project Galactic Guide contains over 1700 articles, but no new articles have been added since 2000; this is probably partly due to the founding of h2g2, a more official project along similar lines.