Wikipedia:Verifiability Information & Wikipedia:Verifiability Links at HealthHaven.com

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This page documents an English Wikipedia policy, a widely accepted standard that all editors should normally follow. Changes made to it should reflect consensus.

Shortcuts: WP:V WP:VERIFY WP:SOURCE

This page in a nutshell: Material challenged or likely to be challenged, and all quotations, must be attributed to a reliable, published source.

The Five Pillars
Content policies
Biographies of living persons Naming conventions Neutral point of view No original research Verifiability What Wikipedia is not

For discussions concerning the reliability of particular sources, see the reliable sources noticeboard.

The threshold for inclusion in Wikipedia is verifiability, not truth—that is, whether readers are able to check that material added to Wikipedia has already been published by a reliable source, not whether we think it is true. Editors should provide a reliable source for quotations and for any material that is challenged or likely to be challenged, or the material may be removed. Since this is the English language version of Wikipedia, English language sources are preferred, but non-English sources are allowed.

Wikipedia:Verifiability is one of Wikipedia's core content policies, along with Wikipedia:No original research and Wikipedia:Neutral point of view. Jointly, these policies determine the type and quality of material that is acceptable in Wikipedia articles. They should not be interpreted in isolation from one another, and editors should therefore familiarize themselves with all three.

Burden of evidence

Policy shortcuts: WP:BURDEN WP:PROVEIT WP:BOP

For how to write citations, see Wikipedia:Citing sources

The burden of evidence lies with the editor who adds or restores material. All quotations and any material challenged or likely to be challenged must be attributed to a reliable, published source using an inline citation. The source should be cited clearly and precisely, with page numbers where appropriate, and must clearly support the material as presented in the article.^[1]

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

Any material lacking a reliable source may be removed, but 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 make reasonable efforts to find sources oneself that support such material, and cite them.

If you want to request a source for an unsourced statement, consider tagging a sentence by adding the {{citation needed}} template, a section with {{unreferencedsection}}, or the article with {{refimprove}} or {{unreferenced}}. Alternatively, you may leave a note on the talk page requesting a source, or move the material to the talk page. Do not leave unsourced or poorly sourced material in an article if it might damage the reputation of living persons or organizations, and do not move it to the talk page.^[2]

Sources

Policy shortcut: WP:SOURCES

Reliable sources

Articles should be based upon reliable, third-party published sources with a reputation for fact-checking and accuracy.^[3] Reliable sources are needed to substantiate material within articles, and citations directing the reader to those sources are needed to give credit to authors and publishers, in order to avoid plagiarism and copyright violations. Sources should directly support the information as it is presented in an article and should be appropriate to the claims made: exceptional claims require high-quality sources.

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 there is disagreement between sources, their views should be clearly attributed in the text.

The most reliable sources are usually peer-reviewed journals; books published by university presses; university-level textbooks; magazines, journals, and books published by respected publishing houses; and mainstream newspapers. Electronic media may also be used, subject to the same criteria. Academic and peer-reviewed publications are highly valued and usually the most reliable sources in areas where they are available, such as history, medicine, and science. Material from reliable non-academic sources may also be used in these areas, particularly if it appears in respected mainstream publications.

For a guideline discussing the reliability of particular types of sources, see Wikipedia:Reliable sources (WP:RS). Because policies take precedence over guidelines, in the case of inconsistency between this page and that one, this page has priority, and WP:RS should be updated accordingly. To discuss the reliability of specific sources, consult the Wikipedia:Reliable sources/Noticeboard.

Just because a source is reliable does not mean it should be included. All articles must adhere to Wikipedia's neutrality policy, fairly representing all majority and significant-minority viewpoints that have been published by reliable sources, in rough proportion to the prominence of each view. Tiny-minority views and fringe theories need not be included, except in articles devoted to them.

Questionable sources

Questionable sources are those with a poor reputation for checking the facts, or with no editorial oversight. Such sources include websites and publications expressing views that are widely acknowledged as extremist, or promotional in nature, or which rely heavily on rumors and personal opinions. Questionable sources should only be used as sources of material on themselves, especially in articles about themselves. (See below.) Questionable sources are generally unsuitable as a basis for citing contentious claims about third parties.

Self-published sources (online and paper)

Policy shortcuts: WP:SELFPUBLISH WP:SPS WP:TWITTER WP:V#SELF

Anyone can create a website or pay to have a book published, then claim to be an expert in a certain field. For that reason self-published media, whether books, newsletters, personal websites, open wikis, blogs, Internet forum postings, tweets, etc., are largely not acceptable.^[4]

Self-published material may, in some circumstances, be acceptable 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. However, caution should be exercised when using such sources: if the information in question is really worth reporting, someone else is likely to have done so.

Similarly, some self-published sources may be acceptable if substantial independent evidence for their reliability is found. For instance, widespread citations without comment by other reputable sources are a good indicator of reliability, while widespread doubts about accuracy weigh against the self-published source. If outside citation is the main indicator of reliability, particular care should be taken to adhere to other guidelines and policies, and to not represent unduly contentious claims. The goal is to reflect established views of sources as far as we can determine them.

Self-published sources should never be used as third-party sources about living persons, even if the author is a well-known professional researcher or writer; see WP:BLP#Reliable sources.

Self-published and questionable sources as sources on themselves

Policy shortcut: WP:SELFPUB

Self-published or questionable sources may be used as sources of information about themselves, especially in articles about themselves, without the requirement that they be published experts in the field, so long as:

the material is not unduly self-serving;
it does not involve claims about third parties;
it does not involve claims about events not directly related to the subject;
there is no reasonable doubt as to its authenticity;
the article is not based primarily on such sources.

Wikipedia and sources that mirror or source information from Wikipedia

Policy shortcut: WP:CIRCULAR

Non-English sources

Policy shortcuts: WP:RSUE WP:VUE WP:NONENG

English-language sources are preferable to sources in other languages so that readers can easily verify the content of the article. However, sources in other languages are acceptable where an English equivalent is not available. Where editors translate a direct quotation, they should quote the relevant portion of the original text in a footnote or in the article. Translations published by reliable sources are preferred over translations made by Wikipedia editors.

Exceptional claims require exceptional sources

Policy shortcut: WP:REDFLAG

Access to sources

Policy shortcuts: WP:Access to sources WP:SOURCEACCESS WP:PAYWALL

Verifiability, in this context, means that anyone should be able to check the sources to verify that material in a Wikipedia article has already been published by a reliable source, as required by this policy and by No original research. 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 copies/excerpts of sources that are not easily accessible.

[0] When there is dispute about whether a piece of text is fully supported by a given source, direct quotes and other relevant details from the source should be provided to other editors as a courtesy.

[1] As Wikipedia co-founder Jimmy Wales has put it: "I can NOT emphasize this enough. There seems to be a terrible bias among some editors that some sort of random speculative 'I heard it somewhere' pseudo information is to be tagged with a 'needs a cite' tag. Wrong. It should be removed, aggressively, unless it can be sourced. This is true of all information, but it is particularly true of negative information about living persons" (Jimmy Wales Zero information is preferred to misleading or false information, WikiEN-l, May 16, 2006, accessed June 11, 2006).

[2] The word "source", as used in Wikipedia, has three meanings: the piece of work itself (an article, book, paper, document), the creator of the work (for example, the writer), and the publisher of the work (for example, The New York Times or Cambridge University Press). All three can affect reliability.

[3] "Blogs" in this context refers to personal and group blogs. Some newspapers host interactive columns that they call blogs, and these may be acceptable as sources so long as the writers are professionals and the blog is subject to the newspaper's full editorial control. Where a news organization publishes the opinions of a professional but claims no responsibility for the opinions, the writer of the cited piece should be attributed (e.g. "Jane Smith has suggested..."). Posts left by readers may never be used as sources.

[4] This idea—that exceptional claims require exceptional sources—has an intellectual history which traces back through the Enlightenment. In 1758, David Hume wrote in An Enquiry Concerning Human Understanding: "No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavors to establish." [1]

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