Wikipedia:Verifiability

WP:V redirects here. For vandalism, see Wikipedia:Vandalism (WP:VAND).

This page documents an English Wikipedia policy.

It describes a widely accepted standard that all editors should normally follow. Changes made to it should reflect consensus.

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This page in a nutshell:

Articles should contain only material that has been published by reliable sources.
Editors adding new material should cite a reliable source, or it may be challenged or removed by any editor.
The obligation to provide a reliable source lies with the editors wishing to include the material, not on those seeking to remove it.

The threshold for inclusion in Wikipedia is verifiability, not truth. "Verifiable" in this context means that any reader should be able to check that material added to Wikipedia has already been published by a reliable source. Editors should provide a reliable source for material that is challenged or likely to be challenged, or it may be removed.

Wikipedia:Verifiability is one of Wikipedia's three content policies. The other two 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 the main namespace. They should not be interpreted in isolation from one another, and editors should try to familiarize themselves with all three. The principles upon which these policies are based are negotiable only at the Foundation level.

Burden of evidence

For how to write citations, see Wikipedia:Citing sources

The burden of evidence lies with the editor who adds or restores material. Any material that is challenged or likely to be challenged needs a reliable source, which should be cited in the article. If an article topic has no reliable, third-party sources, Wikipedia should not have an article on it.

Any edit lacking a source may be removed, but editors may object if you remove material without giving them a chance to provide references. If you want to request a source for an unsourced statement, consider moving it to the talk page. Alternatively, you may tag the sentence by adding the {{fact}} template, or tag the article by adding {{not verified}} or {{unsourced}}. You can also make unsourced sentences invisible in the article by adding  after it, until reliable sources have been provided. Leave a note on the talk page or edit summary explaining what you have done. ^[1]

Be careful not to err too far on the side of not upsetting editors by leaving unsourced information in articles for too long, or at all in the case of information about living people. Jimmy Wales has said of this: "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." ^[2]^[3]

Biographies of living persons

Biographical claims about living people need special care because of the effect they could have on someone's life, and because they could have legal consequences. Remove unsourced or poorly sourced contentious material about living persons immediately and do not move it to the talk page. ^[2]^[3] This applies to the website as a whole, not only to the main namespace.

Sources

See also: Wikipedia:Reliable sources

Articles should rely on reliable, third-party published sources with a reputation for fact-checking and accuracy. Sources should be appropriate to the claims made: exceptional claims require stronger sources.

English-language sources

English-language sources should be given whenever possible, and should always be used in preference to foreign-language sources, so that readers can easily verify that the source material has been used correctly.

Sources of dubious reliability

In general, sources of dubious reliability are sources with a poor reputation for fact-checking or with no fact-checking facilities or editorial oversight. Sources of dubious reliability should only be used in articles about themselves. (See below.) Articles about such sources should not repeat any potentially libellous claims the source has made about third parties, unless those claims have also been published by reliable sources.

Self-published sources (online and paper)

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, personal websites, and blogs are largely not acceptable as sources.

Self-published material may be acceptable when produced by a well-known, professional researcher in a relevant field or a well-known professional journalist. These may be acceptable so long as their work has been previously published by reliable third-party publications. However, exercise caution: if the information in question is really worth reporting, someone else is likely to have done so.

Self-published and dubious sources in articles about the author(s)

Material from self-published sources, and published sources of dubious reliability, may be used as sources in articles about the author(s) of the material, so long as:

it is relevant to their notability;
it is not contentious;
it is not unduly self-serving;
it does not involve claims about third parties, or about events not directly related to the subject;
there is no reasonable doubt as to who wrote it.

Notes

^ 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."
^ ^a ^b Jimmy Wales (2006-05-16). ""Zero information is preferred to misleading or false information"". WikiEN-l electronic mailing list archive. Retrieved 2006-06-11.
^ ^a ^b Jimmy Wales (2006-05-19). ""Zero information is preferred to misleading or false information" (followup post clarifying intent)". WikiEN-l electronic mailing list archive. Retrieved 2006-06-11.