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An Internet encyclopedia is an encyclopedia accessible via the World Wide Web. The idea to build a free encyclopedia using the Internet can be traced at least to the 1993 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.
Digitization of old content 
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 http://1911encyclopedia.org/ by source; a copyright claim was added to the materials, but it probably has no legal validity[original research?]. 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. Probably the most important and successful digitization of an encyclopedia was the Bartleby Project's online adaptation of the Columbia Encyclopedia, tenth Edition, http://www.bartleby.com/65/ in early 2000 and is updated periodically.
Creation of new content 
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.
Encyclopedias that are no longer online 
- Interpedia, 1993
- Nupedia, a slow-moving project to produce a free peer reviewed encyclopedia. Nupedia shut down on September 26, 2003, and much of its content has since been assimilated by Wikipedia.
- GNE, an initiative which did not come to fruition. GNE was abandoned in favour of Nupedia once Nupedia adopted the GNU Free Documentation License.
Current online encyclopedias 
- Baidu Baike – a Chinese collaborative online encyclopedia hosted by the major Chinese search engine Baidu
- Citizendium – a project opened in March 2007 by Larry Sanger
- Conservapedia – a project to create an encyclopedia written from a viewpoint supportive of Conservative Christianity and Young Earth creationism
- Enciclopedia Libre – a Spanish fork of the Spanish Wikipedia, using wiki software, released under the GFDL.
- Encyclopedia of Laser Physics and Technology - a resource covering much of the area of photonics
- Everything2 – has a wider range and does not exclusively focus on building an encyclopedia; its contents are not available under a copyleft license
- h2g2 – a collection of sometimes humorous encyclopedia articles, based on an idea from Douglas Adams's The Hitchhiker's Guide to the Galaxy. Articles are not freely redistributable.
- Hudong – remains to be the largest single-language encyclopedia in the world As of June 2012[update] with 6.4 million articles. Uses its own HDWiki software.
- Cathopedia / Kathpedia – a Catholic Wiki which relies on the Bible as the guiding principle; German and Italian.
- Metapedia – a white nationalist encyclopedia; multiple languages
- New World Encyclopedia, sponsored by the Unification Church
- OrthodoxWiki – a wiki for Orthodox Christianity; multiple languages
- Project Galactic Guide – inspired by The Hitchhiker's Guide to the Galaxy, was one of the first Internet encyclopedia projects
- Scholarpedia – an English-language encyclopedia written by academics
- Te Ara – the online encyclopedia of New Zealand
- Theopedia – Theopedia describes itself as "a growing online evangelical encyclopedia of biblical Christianity, a network of interconnected pages, constantly being refined and updated."
- Wikipedia – the largest encyclopedia (in overall number of articles written in different languages), and the largest in English
- WikiPilipinas – a take on the Wikipedia model from the Philippine point-of-view
Limited scope 
- SourceWatch (formerly Disinfopedia) – a project to expose propaganda and paid spin doctors
- Laptopspedia – a laptops encyclopedia. Contains articles on the subject of technology and laptops.
Several online encyclopedias focus on mathematics:
- MathWorld — a proprietary system hosted at Wolfram Research.
- PlanetMath — a free Wiki-style mathematical encyclopedia which was originally built to replace MathWorld, a proprietary system hosted at Wolfram Research which was down for some time due to legal difficulties. Since MathWorld has returned, PlanetMath has still thrived.
- The QED Project — was a project to establish a "distributed, computerized repository that rigorously represents all important, established mathematical knowledge."