Wikipedia:Verifiability/Draft


 * To discuss particular sources, see the reliable sources noticeboard. For vandalism, see WP:VAND. For the default Wikipedia skin, see WP:VECTOR.

A fundamental requirement for inclusion of content in Wikipedia is verifiability—whether readers can check that material in Wikipedia has already been published by a reliable source. Note that verifiability is a requirement for inclusion, not a guarantee of inclusion. Wikipedia has additional requirements from other policies and guidelines.

To show that it is not original research, all material added to articles must be attributable to a reliable, published source appropriate for the content in question, but in practice you do not need to attribute everything. This policy requires that all quotations and anything challenged or likely to be challenged be attributed in the form of an inline citation that directly supports the material. For how to write citations, see Citing sources.

This policy applies to all material in the mainspace—articles, lists, sections of articles, and captions—without exception, and in particular to material about living persons. Anything that requires but lacks a source may be removed, and unsourced contentious material about living persons must be removed immediately.

Verifiability is one of Wikipedia's core content policies, along with No original research and Neutral point of view. These policies jointly determine the type and quality of material that is acceptable in articles. They should not be interpreted in isolation from one another, and editors should familiarize themselves with the key points of all three. Articles must also comply with the copyright policy.

Assertions of truth and untruth
An editor's assertion that something is true is not enough for inclusion in Wikipedia. It does not matter how convinced you are that some bit of information is true; if the material is unverifiable, do not add it. In this context, Wikipedia requires "verifiability, not truth".

An editor's assertion that something is not true is a more complicated issue. If the dubious information is not supported by a source, it should be challenged; but the question of how to challenge (whether to tag the information as needing a citation or to remove it immediately) depends on the nature of the information (see: WP:Burden, below). If the dubious information is supported by a reliable source, the problem should be discussed on the article talk page, with reference to policy concepts such as the relative reliability of the sources, and maintaining a neutral point of view (specifically regarding due weight). In many situations, a simple rewording - to present the information as an opinion rather than as an accepted fact - can resolve issues of verifiable but potentially untrue information.

Anything challenged or likely to be challenged
All quotations and any material challenged or likely to be challenged must be attributed to a reliable published source using an inline citation. Cite the source clearly and precisely, with page numbers where applicable.

Burden of evidence
The burden of evidence lies with the editor who adds or restores material. You may remove any material lacking a reliable source that directly supports it. How quickly this should happen depends on the material and the overall state of the article. Editors might object if you remove material without giving them time to provide references. It has always been good practice to try to find and cite supporting sources yourself. Do not leave unsourced or poorly sourced material in an article if it might damage the reputation of living people; see here for how the BLP policy applies to groups.

What counts as a reliable source
The word "source" in Wikipedia has three meanings: the work itself (a document, article, paper, or book), the creator of the work (for example, the writer), and the publisher of the work (for example, The New York Times). All three can affect reliability.

Base articles on reliable, third-party, published sources with a reputation for fact-checking and accuracy. Source material must have been published (made available to the public in some form); unpublished materials are not considered reliable. Sources should directly support the material presented in an article and should be appropriate to the claims made. The appropriateness of any source depends on the context. In general, the best sources have a professional structure in place for checking or analyzing facts, legal issues, evidence, and arguments; as a rule of thumb, the greater the degree of scrutiny given to these issues, the more reliable the source.

Where available, academic and peer-reviewed publications are usually the most reliable sources, such as in history, medicine, and science. But they are not the only reliable sources in such areas. Material from reliable non-academic sources may also be used, particularly if it appears in respected mainstream publications. Other reliable sources include university-level textbooks, books published by respected publishing houses, magazines, journals, and mainstream newspapers. Electronic media may also be used, subject to the same criteria. See details in Identifying reliable sources and Search engine test

Newspaper and magazine blogs
Several newspapers host columns they call blogs. These are acceptable as sources if the writers are professionals and the blog is subject to the newspaper's full editorial control. In March 2010, the Press Complaints Commission in the UK ruled that journalists' blogs hosted on the websites of newspapers or magazines are subject to the same standards expected of comment pieces in that organization's print editions. Where a news organization publishes an opinion piece, attribute the writer (e.g. "Jane Smith has suggested..."). Never use posts left by readers as sources. For blogs that are not reliable sources, see below.

Reliable sources noticeboard and WP:IRS
To discuss the reliability of a specific source for a particular statement, consult the reliable sources noticeboard, which seeks to apply this policy to particular cases. For a guideline discussing the reliability of particular types of sources, see Identifying reliable sources (WP:IRS). In the case of inconsistency between this policy and the WP:IRS guideline, or any other guideline related to sourcing, the policy has priority.

Questionable sources
Questionable sources are those with a poor reputation for checking the facts, or which lack meaningful editorial oversight. Such sources include websites and publications expressing views that are widely acknowledged as extremist, or promotional, or which rely heavily on rumor and personal opinion. Questionable sources should be used only as sources of material on themselves, especially in articles about themselves; see below. They are unsuitable for citing contentious claims about third parties.

Self-published sources
Anyone can create a personal web page or pay to have a book published, then claim to be an expert in a certain field. For that reason, self-published media, such as books, patents, newsletters, personal websites, open wikis, personal or group blogs, Internet forum postings, and tweets, are largely not acceptable as sources. Self-published expert sources may be considered reliable when produced by an established expert on the topic of the article whose work in the relevant field has previously been published by reliable third-party publications. Take care when using such sources: if the information in question is really worth reporting, someone else will probably have done so.

Never use self-published sources as third-party sources about living people, even if the author is an expert, well-known professional researcher, or writer.

Self-published or questionable sources as sources on themselves
Self-published and questionable sources may be used as sources of information about themselves, usually in articles about themselves or their activities, without the requirement in the case of self-published sources that they be published experts in the field, so long as:

This policy also applies to pages on social networking sites such as Twitter, Tumblr, and Facebook.
 * 1) the material is not unduly self-serving;
 * 2) it does not involve claims about third parties;
 * 3) it does not involve claims about events not directly related to the source;
 * 4) there is no reasonable doubt as to its authenticity;
 * 5) the article is not based primarily on such sources.

Wikipedia and sources that mirror or use it
Do not use articles from Wikipedia or from websites that mirror its content as sources, because this would amount to self-reference. Similarly, do not use sources that present material originating from Wikipedia to support that same material in Wikipedia, as this would create circular sourcing. Wikipedia may be cited with caution as a primary source of information on itself, such as in articles about itself.

Access to sources
Verifiability in this context means anyone should be able to check that material in a Wikipedia article has been published by a reliable source. The principle of verifiability implies nothing about ease of access to sources: some online sources may require payment, while some print sources may be available only in university libraries. WikiProject Resource Exchange may be able to assist in obtaining source material.

Non-English sources
Because this is the English Wikipedia, English-language sources are preferred over non-English ones, assuming English sources of equal quality and relevance are available.
 * When quoting a source in a different language, provide the original text and an English translation, either in the body of the article or in a footnote.
 * When citing a non-English source for information, it is not always necessary to provide a translation. However, if a question should arise as to whether the non-English original actually supports the information, relevant portions of the original and a translation should be given in a footnote, as a courtesy.

Translations published by reliable sources are preferred over translations by Wikipedians, but translations by Wikipedians are preferred over machine translations. When using a machine translation of source material, editors should be reasonably certain that the translation is accurate and the source is appropriate. When posting original source material, be careful not to violate copyright; see the fair-use guideline.

Tagging a sentence, section, or article
If you want to request a source for an unsourced statement, consider tagging a sentence with the citation needed template by writing cn or fact. Other templates are available here for tagging sections or entire articles. Alternatively, leave a note on the talk page requesting a source, or move the material to the talk page and ask for a source there. To request verification that a reference supports the text, tag it with verification needed. Material that fails verification may be tagged with failed verification or removed. When using templates to tag material, it is helpful to other editors if you explain your rationale in the template, edit summary, or on the talk page.

Special care should be used in regard to material about living people. Unsourced or poorly sourced contentious material about living people should be removed immediately and not tagged or moved to the talk page.

Exceptional claims require exceptional sources
Exceptional claims require high-quality sources. Red flags that should prompt extra caution include:
 * surprising or apparently important claims not covered by mainstream sources;
 * reports of a statement by someone that seems out of character, or against an interest they had previously defended;
 * claims that are contradicted by the prevailing view within the relevant community, or that would significantly alter mainstream assumptions, especially in science, medicine, history, politics, and biographies of living people. This is especially true when proponents say there is a conspiracy to silence them.

Copyright and plagiarism
Take care to avoid plagiarism and breaches of copyright when using sources. Summarize source material in your own words as far as possible; when quoting or closely paraphrasing a source use an inline citation, and in-text attribution where appropriate.

Neutrality
All articles must adhere to the Neutral point of view policy (NPOV), fairly representing all majority and significant-minority viewpoints published by reliable sources, in rough proportion to the prominence of each view. Tiny-minority views need not be included, except in articles devoted to them. Where there is disagreement between sources, use in-text attribution: "John Smith argues that X, while Paul Jones maintains that Y," followed by an inline citation. Sources themselves do not need to maintain a neutral point of view; indeed many reliable sources are not neutral. Our job as editors is simply to present what the reliable sources say.

Notability
If no reliable third-party sources can be found on a topic, Wikipedia should not have an article on it.

Original research
The "No original research" policy (NOR) is closely related to the Verifiability policy. Among its requirements are:
 * 1) All material in Wikipedia articles must be attributable to a reliable published source. This means that a source must exist for it, whether or not it is cited in the article.
 * 2) Sources must support the material clearly and directly: drawing inferences from multiple sources to advance a novel position is prohibited by the NOR policy.
 * 3) Base articles largely on reliable secondary sources. While primary sources are appropriate in some cases, relying on them can be problematic. For more information, see the Primary, secondary, and tertiary sources section of the NOR policy, and the Misuse of primary sources section of the BLP policy.