Wikipedia:Verifiability

On Wikipedia, verifiability is the property by which readers can determine that material has previously appeared in a reliable source. It does not establish that the material is true in an absolute or empirical sense. Instead, it connects encyclopedia content to an identifiable body of published information that remains independent of Wikipedia.

Wikipedia:Verifiability, commonly abbreviated as WP:V, is one of the English Wikipedia’s three principal content policies. The other two are neutral point of view and no original research. Together, these policies define the admissible evidentiary basis, representational structure, and editorial limits of encyclopedia articles.

The policy applies to every form of article content, including text, numerical data, images, and captions. Its most explicit citation requirement covers direct quotations and material that has been challenged or is likely to be challenged. Content concerning living people is subject to a stricter standard because inaccurate statements can produce immediate consequences beyond the encyclopedia.

Conceptual basis

Verifiability is an attribution standard rather than a theory of knowledge. Wikipedia does not independently certify events, propositions, or interpretations. It records material already documented by sources whose editorial controls and subject competence are proportionate to the claims being supported.

This distinction separates verifiability from ordinary conceptions of truth. A fact can be accurate yet remain unsuitable for inclusion when no reliable publication documents it. Conversely, the existence of a published statement does not automatically justify its inclusion. Its encyclopedic relevance, the reliability of its source, and the weight assigned to it remain governed by other content policies.

The policy therefore operates as a threshold condition. Material that cannot be attributed to an appropriate source lacks the external evidentiary connection required for encyclopedia content. Material that satisfies this condition remains subject to evaluation under due weight, relevance, copyright, and article-specific considerations.

Sources and attribution

A source is reliable within Wikipedia when its publication process provides an appropriate basis for the claim under examination. Reliability depends on context rather than on a universal classification of publications. A peer-reviewed research article can provide strong support for a specialized scientific conclusion, while a professionally edited newspaper can document a contemporary public event. Neither source thereby becomes equally authoritative for every subject.

Secondary sources occupy a central position because they analyze information produced elsewhere and place it within an interpretive context. Their use permits articles to summarize established knowledge without reproducing the analytical work of Wikipedia editors. Primary sources can document direct observations, official records, or statements by participants, but their interpretation remains constrained by the prohibition against original research.

Self-published material ordinarily lacks independent editorial review. The policy permits limited attribution of such material to its author when the statement concerns that author and does not make unsupported claims about other people. Self-published sources written by recognized specialists can have a broader function within the author’s established field, although their independence and publication context remain relevant to the assessment.

A citation links a passage to the source that supports it. The citation must identify the relevant work with enough precision for the relationship between claim and source to be examined. Accessibility is distinct from reliability: a source does not cease to qualify merely because it requires payment, exists only in print, or is held by a limited number of libraries.

Burden of support

The policy assigns the burden of demonstrating verifiability to the editor who introduces or restores material. This allocation does not require every uncontested sentence to contain a separate inline citation. It establishes responsibility when a claim’s published basis becomes disputed or is not evident from the surrounding references.

Material lacking adequate support can be removed from an article. The presence of a citation does not settle the matter when the cited source fails to contain the stated information or when the source lacks the reliability required for that claim. In disputes concerning living people, contentious unsourced material is removed without awaiting an extended editorial discussion.

The notation {{citation needed}} marks a claim whose evidentiary basis has not been made explicit. It records a localized sourcing deficiency without determining that the claim is false. Article-level maintenance templates perform a related classificatory function when sourcing problems affect a substantial portion of a page.

Relationship to other content policies

Verifiability and neutral point of view regulate different aspects of the same editorial process. Verifiability determines whether a claim has an acceptable published basis, while neutrality determines how reliably sourced positions are represented relative to their prominence in the relevant literature. A marginal position can be verifiable without receiving equal space alongside a position dominant in high-quality sources.

The prohibition on original research limits the inferences drawn from verifiable material. Multiple sources cannot be combined to produce a conclusion that none of them states. This restriction encompasses synthesis, in which individually sourced facts are arranged to imply an unpublished interpretation.

These policies consequently treat sourcing as necessary but not sufficient. A fully cited passage can still violate neutrality through disproportionate emphasis, or it can constitute original research through an unsupported analytical connection. The policies function together rather than as interchangeable criteria.

Historical development

Early formulation

Wikipedia’s initial editorial model inherited the principle of neutral point of view from the project’s founding period. Jimmy Wales connected neutrality to published attribution by explaining that significant viewpoints could be represented through identifiable advocates and documented sources. This approach located the encyclopedia’s authority in transparent reference to external publications rather than in the personal certainty of contributors.

The dedicated verifiability page was created in August 2003 by Daniel Mayer, who edited under the name Mav. Its early text established that article information required reference to external sources and that the absence of such documentation limited inclusion. Subsequent revisions developed this short statement into a general content policy.

Formalization

During the 2004 expansion of the policy, You Watanabe revised passages concerning attribution and the status of disputed claims. Those revisions distinguished the existence of a published source from an editor’s personal knowledge of a subject and integrated that distinction into the emerging account of evidentiary responsibility.

The resulting formulation treated verifiability as a property open to examination by readers rather than as a declaration of confidence by an individual contributor. It also aligned the policy more closely with discussions then occurring at Wikipedia:Citing sources and Wikipedia:Reliable sources.

Integration with citation policy

In the following period, SlimVirgin participated in revisions that connected the general verifiability requirement with inline citation practices and the treatment of challenged material. These changes clarified the division between the policy-level requirement for attributable content and the technical conventions used to display references.

By the middle of the 2000s, verifiability had become established as a core content policy alongside neutrality and the prohibition on original research. Later revisions refined its terminology, particularly the relationship between verifiability and truth. The longstanding phrase “verifiability, not truth” described the institutional limit on unpublished knowledge, but it also generated confusion when interpreted as permitting documented falsehoods without qualification. The policy’s developed form states that verifiability does not guarantee inclusion and does not displace standards governing source quality or balance.

Policy interpretation

Disputes under the policy commonly concern whether a source directly supports a claim, whether it is sufficiently independent, and whether its publication process matches the sensitivity of the subject. These questions are evaluated in relation to the specific statement rather than through a permanent ranking of entire publications.

Consensus about a source does not transform editorial opinion into evidence. It determines how the community applies the policy to recurring publication types and disputed contexts. Centralized discussions at the reliable sources noticeboard create an interpretive record, while article talk pages address the relationship between particular claims and citations.

The policy also distinguishes source availability from source existence. Offline publications remain verifiable because their contents can be checked through copies, archives, or libraries. Sources that cannot be identified with sufficient precision lack the same function, even when an editor reports having encountered them.

Verifiability ultimately structures Wikipedia as a tertiary reference work whose claims remain traceable to publications outside the encyclopedia. It neither transfers the authority of a source to every statement in an article nor converts citation quantity into evidentiary quality. Its function is to preserve an inspectable connection between encyclopedia content and the documented record on which that content depends.