An online encyclopedia is an encyclopedia accessible through the internet, such as Everipedia and Wikipedia. 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. ^[2]

In January 1995, Project Gutenberg started to publish the ASCII text of the Encyclopædia Britannica , 11th edition (1911), but disagreement about the method halted the work after the first volume. For trademark reasons this has been published as the Gutenberg Encyclopedia . In 2002, ASCII text of and 48 sounds of music was published on Encyclopædia Britannica Eleventh Edition ^[undefined] by source; a copyright claim was added to the materials included. Project Gutenberg has restarted work on digitising and proofreading this encyclopedia; as of June 2005 it had not yet been published. Meanwhile, in the face of competition from rivals such as Encarta, the latest Britannica was digitized by its publishers, and sold first as a CD-ROM and later as an online service. Other digitization projects have made progress in other titles. One example is Easton's Bible Dictionary (1897) digitized by the Christian Classics Ethereal Library. ^[undefined] Probably the most important and successful digitization of an encyclopedia was the Bartleby Project's online adaptation of the Columbia Encyclopedia , tenth Edition, ^[undefined] in early 2000 and is updated periodically.

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 ^[undefined] 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.