Wikipedia:Verifiability

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This page documents an official English Wikipedia policy, a widely accepted standard that all users should follow. When editing this page, please ensure that your revision reflects consensus. If in doubt, consider discussing changes on the talk page.
This page in a nutshell: Material challenged or likely to be challenged, and all quotations, must be attributed to a reliable, published source.
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"WP:V" redirects here. For information on vandalism, see the vandalism policy. To discuss 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 is likely to be challenged, or the material may be removed.

Wikipedia:Verifiability is one of Wikipedia's core content policies. The others are 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 familiarize themselves with all three.

Contents

[edit] Burden of evidence

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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 should be attributed to a reliable, published source using an inline citation.[1]

The source should be cited clearly and precisely to enable readers to find the text that supports the article content in question. Editors should cite sources fully, providing as much publication information as possible, including page numbers for book sources and direct quotes if challenged.

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 editors may object if you remove material without giving them sufficient time to provide references. If you want to request a source for an unsourced statement, consider tagging a sentence by adding the {{fact}} template, a section with {{unreferencedsection}}, or the article with {{refimprove}} or {{unreferenced}}. Alternatively, you may move the material to the talk page (unless it is unsourced or poorly sourced contentious material about a living person, in which remove it entirely). You may also leave a note on the talk page or an invisible HTML comment on the article page.[2]

Do not leave unsourced or poorly sourced information that may damage the reputation of living persons or organizations in articles (See Wikipedia:Biographies of living persons for details of this policy). As 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 [3]

[edit] Sources

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See also: Wikipedia:Neutral point of view, Wikipedia:Biographies of living persons, and Wikipedia:No original research#Primary, secondary, and tertiary sources

[edit] Reliable sources

Articles should rely on reliable, third-party published sources with a reputation for fact-checking and accuracy.[4] Reliable sources are necessary both to substantiate material within articles and 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 reliable sources.

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.

In general, the most reliable sources are peer-reviewed journals and books published in university presses; university-level textbooks; magazines, journals, and books published by respected publishing houses; and mainstream newspapers. As a rule of thumb, the greater the degree of scrutiny involved in checking facts, analyzing legal issues, and scrutinizing the evidence and arguments of a particular work, the more reliable it is.

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 they are respected mainstream publications. The appropriateness of any source always depends on the context. Where there is disagreement between sources, their views should be clearly attributed in the text.

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 an 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.

[edit] Questionable sources

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Questionable sources are those with a poor reputation for fact-checking. Such sources include websites and publications that express views that are widely acknowledged as extremist, are promotional in nature, or rely heavily on rumors and personal opinions. Questionable sources should only be used as sources about themselves as described below. Articles about such sources should not repeat any contentious claims the source has made about third parties, unless those claims have also been published by reliable sources.

[edit] Self-published sources

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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 books, newsletters, personal websites, open wikis, blogs, forum postings, and similar sources are largely not acceptable.[5]

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.

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.

Articles and posts on Wikipedia may not be used as sources.

[edit] Self-published and questionable sources about themselves

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Self-published and questionable sources may only be used as sources about themselves, and only if:

  1. the material used is relevant to their notability;
  2. it is not contentious;
  3. it is not unduly self-serving;
  4. it does not involve claims about third parties;
  5. it does not involve claims about events not directly related to the subject;
  6. there is no reasonable doubt as to who authored it;
  7. the article is not based primarily on such sources.

[edit] Non-English sources

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Because this is the English Wikipedia, for the convenience of our readers, editors should use English-language sources in preference to sources in other languages, assuming the availability of an English-language source of equal quality, so that readers can easily verify that the source material has been used correctly. Where editors use a non-English source to support material that others might challenge, or translate any direct quote, they need to quote the relevant portion of the original text in a footnote or in the article, so readers can check that it agrees with the article content. Translations published by reliable sources are preferred over translations made by Wikipedia editors.

[edit] Exceptional claims require exceptional sources

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See also: Wikipedia:Fringe theories

Certain red flags should prompt editors to examine the sources for a given claim:

  • surprising or apparently important claims not covered by mainstream sources;
  • reports of a statement by someone that seems out of character, embarrassing, controversial, or against an interest they had previously defended;
  • claims that are contradicted by the prevailing view within the relevant community, or which would significantly alter mainstream assumptions, especially in science, medicine, history, politics, and biographies of living persons. This is especially true when proponents consider that there is a conspiracy to silence them.

Exceptional claims in Wikipedia require high-quality reliable sources; if such sources are not available, the material should not be included. Also be sure to adhere to other policies, such as the policy for biographies of living persons and the undue weight provision of Wikipedia:Neutral point of view.

[edit] See also

[edit] Notes and references

  1. ^ When content in Wikipedia requires direct substantiation, the established convention is to provide an inline citation to the supporting references. The rationale is that this provides the most direct means to verify whether the content is consistent with the references. Alternative conventions exist, and are acceptable when they provide clear and precise attribution for the article's assertions, but inline citations are considered "best practice" under this rationale. For more details, please consult Wikipedia:Citing_sources#How_to_cite_sources.
  2. ^ See Help:Editing#Basic text formatting: "Invisible comments to editors only appear while editing the page. If you wish to make comments to the public, you should usually go on the talk page."
  3. ^ Jimmy Wales (2006-05-16). "Zero information is preferred to misleading or false information". WikiEN-l electronic mailing list archive. Retrieved on 2006-06-11.
  4. ^ The word "source", as used in Wikipedia, has three related meanings: the piece of work itself, the creator of the work, and the publisher of the work. All three affect reliability.
  5. ^ "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.

[edit] Further reading