Wikipedia is a multilingual encyclopedia published on the World Wide Web, whose articles are written and maintained primarily by volunteers. It combines an openly editable wiki platform with editorial policies, public revision histories, and community oversight. The nonprofit Wikimedia Foundation hosts the project and supports its technical infrastructure, while contributor communities generally determine article content. Wikipedia is free to read, and most of its text can be reused under specified licensing conditions. (en.wikipedia.org)
Origins and development
Wikipedia began on January 15, 2001, through the work of Jimmy Wales, Larry Sanger, and other early participants. It developed alongside Nupedia, an online encyclopedia that used a formal expert-review process. The wiki approach initially offered a faster way to draft material, but Wikipedia soon developed into a separate project. Its name combines “wiki,” a type of collaboratively editable website, with “encyclopedia.” (en.wikipedia.org)
The principal organizational change came in 2003, when the Wikimedia Foundation was established to support Wikipedia and related projects. English Wikipedia reached one million articles in 2006. Expansion into additional languages made Wikipedia a collection of separately maintained encyclopedias rather than a single encyclopedia translated uniformly into many languages. (wikimediafoundation.org)
Wikipedia’s development also established a distinction between its publishing model and those of conventional reference works. Instead of issuing fixed editions prepared by a selected editorial staff, it maintains articles through continuing contributions and revisions. The published text of an article is therefore a particular state in an ongoing editorial process, not necessarily a finished or permanently approved account. (en.wikipedia.org)
Collaborative editing and technical structure
Wikipedia uses MediaWiki, a free and open-source software platform designed for wiki publishing. The software supports linked pages and collaborative editing; the Wikimedia Foundation supplies the infrastructure and develops tools used by contributors. MediaWiki is not identical to Wikipedia: it also powers other websites. (mediawiki.org)
The basic unit is a page. Encyclopedia articles occupy the main article space, while other page types serve discussion, contributor coordination, documentation, and administration. An article normally has an associated talk page, where editors can discuss sources, wording, scope, and disagreements. Revision histories record successive versions, allowing contributors to compare changes and restore earlier text. Hypertext links connect related articles and help readers navigate between subjects. (en.wikipedia.org)
Open editing does not mean that every person can change every page at all times. Restrictions may apply to particular pages or contributors. Protection can limit editing when a page experiences persistent disruption or other specified problems, and some systems allow changes to be reviewed before they are displayed to certain readers. These mechanisms qualify, rather than eliminate, the project’s general commitment to broad participation. (en.wikipedia.org)
Editorial principles
Wikipedia’s broad principles are commonly expressed through five pillars: it is an encyclopedia; it seeks neutral presentation; its content is free to use and edit; contributors should interact respectfully; and rules should serve the improvement of the encyclopedia rather than become ends in themselves. Detailed implementation depends on the relevant language community. (en.wikipedia.org)
On English Wikipedia, three closely connected policies govern the substance of articles:
- Neutral point of view. Articles should describe significant published viewpoints fairly and in proportion to their prominence in reliable sources. Neutrality does not require giving equal space to every assertion, or treating an unsupported position as equivalent to a well-established one. (en.wikipedia.org)
- Verifiability. Readers should be able to check article content against reliable published sources. Quotations and material that is challenged or likely to be challenged require citations that support the statements being made. An editor’s personal certainty is not a substitute for a source. (meta.wikimedia.org)
- No original research. Wikipedia does not provide a venue for publishing new findings or editors’ unpublished interpretations. It also excludes novel conclusions produced by combining sources in ways those sources do not support. (en.wikipedia.org)
These rules make Wikipedia a synthesis of existing publications rather than an institution that independently establishes new knowledge. Sources must be appropriate to their context, and the existence of a citation alone does not establish that a claim has been represented accurately. (en.wikipedia.org)
Article inclusion is also governed by scope and notability criteria. Wikipedia is not intended to be an indiscriminate directory, advertising service, personal publishing platform, or repository for every true statement. The criteria for a stand-alone article are distinct from the question of whether a particular detail belongs in an existing article. (en.wikipedia.org)
Community governance and institutional support
Wikipedia’s governance combines local community decision-making with foundation-wide obligations. Contributors develop and enforce policies for individual project editions, while the Wikimedia Foundation maintains the hosting service and sets requirements through instruments such as its terms of use. Consequently, neither “anyone can edit” nor “the foundation runs Wikipedia” fully describes how editorial authority operates. (foundation.wikimedia.org)
Volunteer participation includes more than writing prose. Contributors evaluate sources, correct errors, organize pages, review changes, and address disruptive activity. Administrative permissions provide additional technical capabilities, including some forms of page protection, but do not replace the need to apply community policies. (en.wikipedia.org)
Wikipedia does not fund ordinary reading access through commercial advertising or subscriptions. Donations support the Wikimedia Foundation’s work on Wikipedia, related projects, and their infrastructure. This institutional funding is separate from the predominantly volunteer production of encyclopedia content. (wikimediafoundation.org)
Language editions and related projects
Wikipedia’s language editions differ in size, coverage, contributor participation, and local editorial practices. They are not simply synchronized copies of English Wikipedia. Articles on the same subject may have different structures, references, emphases, and levels of development. Research on cross-language information gaps examines how these editions can contain complementary rather than identical information. (en.wikipedia.org)
Wikipedia is one project within a wider Wikimedia ecosystem. Wikimedia Commons provides a shared media repository, while Wikidata maintains structured statements and identifiers. Wikidata also connects corresponding pages across language editions and supplies data that Wikimedia projects can use. Its structured records are distinct from Wikipedia’s narrative articles. (en.wikipedia.org)
Licensing and reuse
The word “free” describes both access and permissions for reuse. Wikipedia’s text is generally available under the Creative Commons Attribution–ShareAlike 4.0 International license; much of it is additionally available under the GNU Free Documentation License. The applicable conditions depend on the material and its licensing history. (foundation.wikimedia.org)
The Attribution–ShareAlike license permits copying, redistribution, and adaptation, including commercial use, subject to its conditions. These include appropriate attribution, identification of modifications, and compatible share-alike licensing when adaptations are distributed. Freely licensed content is therefore not necessarily public-domain content: copyright can remain in force while broad permissions are granted. (creativecommons.org)
Images and other media require separate attention because their licenses may differ from those of article text. Some material is freely licensed, some is in the public domain, and some is used under limited exceptions. Wikipedia’s trademarks are likewise distinct from the licenses covering encyclopedia content. (foundation.wikimedia.org)
Reliability, coverage, and limitations
Wikipedia’s policies describe intended standards, not a guarantee that every article meets them. Research has identified missing citations, references that do not satisfy verification requirements, and other content-reliability problems. Assessment therefore concerns particular claims and article versions, rather than assuming uniform quality across the entire encyclopedia. (arxiv.org)
Open editing creates opportunities both for correction and for disruption. Page-protection mechanisms address persistent vandalism and related problems, but their existence does not imply that all changes receive advance review. The revision record makes editorial changes traceable, while the accuracy of the resulting text remains dependent on sources and contributor scrutiny. (en.wikipedia.org)
Coverage is also uneven. The Wikimedia Foundation has documented gender imbalances in contributor participation and biographical coverage, and initiatives such as Women in Red seek to improve representation. Wikipedia’s reliance on published sources creates a further constraint: subjects poorly documented in the available literature are harder to cover within its sourcing rules. (wikimediafoundation.org)
Research and artificial intelligence
Wikipedia is used not only as a reference work but also as material for computational research. Its text has supplied training data for natural language processing and large language models. These uses extend the influence of its content beyond readers who visit the encyclopedia directly. (wikimediafoundation.org)
The relationship with artificial intelligence also affects Wikipedia’s own maintenance. The Wikimedia Foundation develops automated and machine-learning tools to assist contributors, while emphasizing human-led moderation and governance. Its AI strategy announced in April 2025 framed such tools as support for volunteers rather than a replacement for community authorship. (wikimediafoundation.org)
References
- Wikipedia:Abouten.wikipedia.org
- Wikimedia Foundation Terms of Usefoundation.wikimedia.org
- History of Wikipediaen.wikipedia.org
- Celebrating 20 years of Wikipediawikimediafoundation.org
- MediaWikimediawiki.org
- Technologywikimediafoundation.org
- Wikipediaen.wikipedia.org
- Wikipedia:Protection policyen.wikipedia.org
- Wikipedia:Five pillarsen.wikipedia.org
- Wikipedia:Neutral point of viewen.wikipedia.org
- Training modules/dashboard/slides/10311-verifiabilitymeta.wikimedia.org