This page provides examples of what editors on Wikipedia have assessed to be a reliable source. The advice is not, and cannot be, comprehensive, and should be used primarily to inform discussion in an article talk page with respect to sources. Exceptions can naturally be made using common sense, in order to reach a collaborative conclusion. Advice can be sought on the talk page of this essay.

You can discuss reliability of specific sources at Wikipedia:Reliable sources/Noticeboard.

Posts on Usenet are rarely regarded as reliable sources, because they are easily forged or misrepresented, and many are anonymous or pseudonymous.

One exception is that some authorities on certain topics have written extensively on Usenet, and their writings there are vouched for by them or by other reliable sources. A canonical example is J. Michael Straczynski, the creator of the television series Babylon 5, who discussed the show at length on Usenet. His postings are archived and authenticated on his website, and may be an acceptable source on the topic of Babylon 5 under the self-publication provision of verifiability policy.

In many cases, no. Most private weblogs ("blogs"), especially those hosted by blog-hosting services such as Blogger, are self-published sources; many of them published pseudonymously. There is no fact-checking process and no guarantee of quality of reliability. Information from a privately-owned blog may be usable in an article about that blog or blogger under the self-publication provision of the verifiability policy.

Weblog material written by well-known professional researchers writing within their field may be acceptable, especially if hosted by a university, newspaper or employer (a typical example is Language Log, which is already cited in several articles, e.g. Snowclone, Drudge Report). Usually, subject experts will publish in sources with greater levels of editorial control such as research journals, which should be preferred over blog entries if such sources are available.

Blogs may be used in certain conditions as secondary sources on living persons; see WP:BLP.

Web forums and the talkback section of weblogs are rarely regarded as reliable. While they are often controlled by a single party (as opposed to the distributed nature of Usenet), many still permit anonymous commentary and we have no way of verifying the identity of a poster. Some however, are edited by reliable organizations, and therefore may possibly be justified as exceptions.

Wikis, including Wikipedia and other wikis sponsored by the Wikimedia Foundation, are not regarded as reliable sources. However, wikis are excellent places to locate primary and secondary sources. Many of them license content under the GFDL, which might be worth importing into Wikipedia, but once imported, the material is subject to Wikipedia:Attribution and Wikipedia:Neutral point of view.

If circumstances require linking to a wiki page — for example, if the wiki itself is a notable project — it is best to use the permalink feature common on wiki software. Common wiki platforms, including the MediaWiki software which underlies Wikipedia, incorporate a feature allowing one to link directly to a version of a page as it existed some time in the past. To illustrate, this hyperlink points to revision 118386243 (dated 2007-03-28) of the article Encyclopedia, and will reference that individual revision indefinitely. When using the Cite Web template, specify both the date of the page revision you are citing and the date you retrieved that revision, as follows:

{{cite web
| url = http://en.wikipedia.org/w/index.php?title=Encyclopedia&oldid=118386243
| title = Encyclopedia
| accessdate = 2007-03-30
| author = Wikipedia contributors
| authorlink = Wikipedia community
| date = 2007-03-28
| publisher = Wikipedia, The Free Encyclopedia
| language = English
}}

This example would render as follows:

Wikipedia contributors (2007-03-28). "Encyclopedia". Wikipedia, The Free Encyclopedia. Retrieved 2007-03-30. {{cite web}}: |author= has generic name (help)

• IRC: Transcripts of chatroom sessions are not reliable sources because they are unpublished, and we have no way of knowing who the authors are. Transcripts are also easily forged or altered.
• Myspace: Myspace is generally not acceptable even as a self-published source, because most of it is anonymous or pseudonymous. If the identity of the author can be confirmed in a reliable, published source, then it can be used with the caution appropriate to a self-published source.
• Facebook: Facebook is generally not acceptable as a reliable source, as anyone may create a page and add comments, and there is no stringent checking of a user's real name and age. On occasion, Facebook pages that are clearly marked as official pages for notable subjects, with direct link to those pages from official websites, in which case they may be used as primary sources. Note, however, that if a public figure says something noteworthy in an official Facebook account (or from another social media site, for that matter), it is likely that the media will report this anyway.
• YouTube: YouTube and other video-sharing sites are generally not considered reliable sources because anyone can create or manipulate a video clip and upload without editorial oversight, just as with a self-published website. However, official channels of notable organizations, such as Monty Python's channel, may be acceptable as primary sources if their authenticity can be confirmed, or as a secondary source if they can be traced to a reliable publisher. Videos may also be used as a convenience link for material originally published elsewhere. In all cases, care should be undertaken to ensure that the video is genuinely authorized by the copyright holder. Be careful not to link to material that is a copyright violation. In general, unless the video is clearly marked as "official" with a name strongly identified with the notable publisher or source, best practice is to treat it as a copyright violation and not use it.

A patent is a limited monopoly granted by a government to an inventor, in return for the inventor disclosing his invention (instead of, for example, attempting to maintain it as a trade secret).

An issued patent may be considered a reliable source for the existence of the patent (or application), the names of the inventors, the date of the patent, and a straightforward description of what was invented.

Government patent authorities, however, do not fact-check, edit, or endorse any material in the patent application. Their main concern, as regards conditions for publishing an application (not an issued patent), is whether the application conforms to the required legal form and content under the that government agency's regulations. The primary responsibility of patent authorities is to verify that the inventions claimed are clearly delineated, non-obvious, and novel (that is, not previously described in the literature, whether in a patent or elsewhere).

Patent applications and issued patents must be treated as self-published, non-independent, primary sources for Wikipedia purposes. A patent application is written by the inventor-applicant, and patent authorities have essentially no control over its content or whether it gets published. A patent may be published (i.e., on the government website, at the sole discretion and direction of the patent applicant) before the patent office has agreed that the claimed invention merits a patent.

The content of a patent should be considered somewhat less reliable. Patent examiners do not replicate any experiments, build any devices, or decide whether any tests run by the inventor were done correctly. They have no way of knowing whether information provided by the inventor is accurate or whether the invention will work as described. Patent authorities:

• do not control the content of an issued patent (other than prescribing the format);
• do not attempt to verify that the inventions described actually provide whatever benefits are claimed in the patent, or that results of experiments were actually as described; and
• do not pass judgment on whether the ideas offered in the patent are scientifically accurate.

Thus both issued patents and patent applications have limited use as sources on Wikipedia:

• They are reliable as a citation to the existence of an invention and its date: "A patent was issued to Alice Expert on May 5, 2010...".
• They are reliable for attributed statements about their contents: "According to five-year-old inventor Steven Olson in his application for US Patent #6,368,227, issued in 2002, he invented swinging sideways because swinging back and forth might get boring."

Noting the existence of patents or patent applications is a common form of puffery for businesses. Avoid giving too much emphasis to their existence or contents.

The {{patent}} template can be used for simple citation of patents.

Verifying birth dates and other basic biographical information can be a challenge. Birth certificates provide reasonably accurate information, but since two people with the same name could have been born, there is usually no way to prove that this particular birth certificate is for the subject of the article. Additionally, some sources, such as baseball cards and claims made by actors and other entertainers, are routinely and deliberately falsified to advance the person's career in an industry that discriminates against older people.

Statistical data may take the form of quantitative or qualitative material, and analysis of each of these can require specialised training. Statistical data should be considered a primary source and should be avoided. Misinterpretation of the material is easy and statistics are frequently reported ambiguously in the media, so any secondary reference to statistical data should be treated with considerable care.

The integrity of qualitative data depends on the questions used and the demographic make-up of the samples questioned; sound secondary sources will comment on the impact of the questioning strategy and the sample questioned and this should be referred to in the article.

See Misuse of statistics, Opinion poll, and Statistical survey for common errors and abuses.

When writing history articles the B-Class criteria of WP:History should be followed, these are The Wikipedia Military History Manual of Style requirements.

Briefly: published scholarly sources from academic presses should be used.

Historical research involves the collection of original or “primary” documents (the job of libraries and archives), the close reading of the documents, and their interpretation in terms of larger historical issues. In recent decades, many more primary documents (such as letters and papers of historical figures) have been made easily available in bound volumes or online. For instance, the Jefferson Papers project at Princeton begun in 1950 has just published volume 30, reaching February 1801. More recently, primary sources have been put online, such as the complete run of the The Times, the New York Times and other major newspapers. Some of these are proprietary and must be accessed through libraries; others, such as “Making of America”, which publishes 19th century magazines, are open to the public.

Scholars doing research publish their results in books and journal articles. The books are usually published by university presses or by commercial houses like W.W. Norton and Greenwood which emulate the university press standards. Reputable history books and journal articles always include footnotes and bibliographies giving the sources used in great detail. Most journals contain book reviews by scholars that evaluate the quality of new books, and usually summarize some of their new ideas. The American Historical Review (all fields of history) and Journal of American History (US history) each publish 1000 or more full-length reviews a year. Many of the major journals are online, as far back as 1885, especially through JSTOR.org. A good book or article will spell out the historiographical debates that are ongoing, and alert readers to other major studies.

On many topics, there are different interpretive schools which use the same documents and facts but use different frameworks and come to different conclusions. Useful access points include: scholar.google.com and books.google.com, and (through libraries) ABC-CLIO’s two abstract services, American: History and Life (for journal articles and book reviews dealing with the US and Canada), and Historical Abstracts (for the rest of the world.) Research libraries will hold paper guides to authoritative sources. The most useful is The American Historical Association's Guide to Historical Literature, edited by Mary Beth Norton and Pamela Gerardi 2 vol (1995), which is an annotated bibliography of authoritative sources in all fields of history.

In historical pages the user is assisted by having an annotated bibliography of the best resources. Users will often have to use inter-library loan to obtain books, so a short annotation explaining the value and POV of the book may be helpful.

There are many other sources of historical information, but their authority varies. A recent trend is a proliferation of specialized encyclopedias on historical topics. These are edited by experts who commission scholars to write the articles, and then review each article for quality control. They can be considered authoritative for Wikipedia. General encyclopedias, like the Encyclopedia Britannica or Encarta, sometimes have authoritative signed articles written by specialists and including references. However, unsigned entries are written in batches by freelancers and must be used with caution.

College textbooks are updated every few years, are evaluated by many specialists, and usually try to keep abreast of the scholarship, but they are often without footnotes and usually do not spell out the historiographical debates. Textbooks at the K-12 level do not try to be authoritative and should be avoided by Wikipedia editors. Every place has guide books, which usually contain a capsule history of the area, but the great majority do not pretend to be authoritative.

Textbooks in various academic disciplines often include a historical introduction to the discipline. The authors of these introductions are seldom as familiar with the historical literature as they are with their discipline itself. They write these introductions to provide some background to the discipline as it is currently practiced and to inculcate students into the values of the discipline. Such historical introductions should not be treated as historical research and should be used with caution.

On many historical topics there are memoirs and oral histories that specialists consult with caution, for they are filled with stories that people wish to remember—and usually recall without going back to the original documentation. Editors should use them with caution.

The general public mostly gets its history from novels, films, TV shows, or tour guides at various sites. These sources are full of rumor and gossip and false or exaggerated tales. They tend to present rosy-colored histories in which the well-known names are portrayed heroically. Almost always editors can find much more authoritative sources.

Scientific journals are the best place to find primary-source articles about randomized experiments, including randomized controlled clinical trials in medicine. Every serious scientific journal is peer-reviewed. Many articles are excluded from peer-reviewed journals because they report what is in the opinion of the editors unimportant or questionable research. In particular, be careful of material in a journal that is not peer-reviewed, or one that reports material in a field different from its usual focus. (See: Marty Rimm affair.) Be careful of articles published in disreputable fields or disreputable journals. (See Sokal affair.)

The fact that a statement is published in a refereed journal does not make it true. Even a well-designed randomized experiment is expected to produce seriously flawed results from time to time (with low probability). Experiments and other studies have fallen victim to deliberate fraud. (See: Retracted article on neurotoxicity of ecstasy, and Schön affair.)

Honesty and the policies of neutrality and no original research demand that we present the prevailing "scientific consensus". Polling a group of experts in the field wouldn't be practical for many editors but often there is an easier way. The scientific consensus can be found in recent, authoritative review articles, textbooks, major up-to-date reference works such as medical dictionaries or scientific encyclopedias, and some forms of monographs. Be aware that many such reference works are many steps removed from the primary literature, and may well be out-of-date in terms of the current consensus. Beware of the over-simplifications likely to be found in condensed dictionaries and encyclopedias.

There is sometimes no single prevailing view because the available evidence does not yet point to a single answer. Because Wikipedia not only aims to be accurate, but also useful, it tries to explain the theories and empirical justification for each school of thought, with reference to published sources. Editors must not, however, create arguments themselves in favor of, or against, any particular theory or position. See Wikipedia:No original research, which is policy. Significant-minority views are welcome in Wikipedia, but must be identified as minority views and not given the same depth of coverage as the majority view. The views of tiny minorities need not be reported. (See Wikipedia:Neutral Point of View.)

Make readers aware of any uncertainty or controversy. A well-referenced article will point to specific journal articles or specific theories proposed by specific researchers.

Articles in newspapers and popular magazines generally lack the context to judge experimental results. They may emphasize the most extreme possible outcomes mentioned in a research project and gloss over caveats and uncertainties, for instance presenting a new experimental medicine as the "discovery of the cure" of a disease. Also, newspapers and magazines sometimes publish articles about scientific results before those results have been peer-reviewed or reproduced by other experimenters. They also tend not to report details of the methodology that was used, or the degree of experimental error. Thus, popular newspaper and magazine sources are generally not the best sources for scientific and medical results, especially in comparison to the academic literature.

What can a popular-press article on scientific research provide? The mainstream press is valuable for reporting the public perception of scientific topics and for summarizing their implications for public policy. Such articles can also be used as pointers to more substantive information on the science itself. For instance, a newspaper article quoting Joe Smith of the Woods Hole Oceanographic Institution regarding whales' response to sonar gives you a strong suggestion of where to go to find more: look up his work on the subject, and cite his published papers instead of the newspaper article.

The vast majority of well-regarded journals are indexed in the ISI Web of Science. One method to determine which journals are held in high esteem by scientists is to look at impact factor ratings as provided by Journal Citation Reports, which track how many times articles in a given journal are cited by later articles. Be aware that these impact factors are not comparable across different academic fields and specialties; the relative rank of a journal among others in its field is the best indicator.

PubMed is a search engine that gives access to MEDLINE, an indexing service for peer-reviewed articles in the fields of medicine and biology: it includes all journals in the area, and the quality depends on the journal. In medicine, the New England Journal of Medicine, the Journal of the American Medical Association (JAMA), the Lancet, and the BMJ (British Medical Journal) are traditionally considered the top titles.

The American Association for the Advancement of Science's journal Science, along with Nature are among the most notable general scholarly publications; Cell is especially well known in its field of experimental molecular biology.

Keep in mind that even a reputable journal may occasionally post a retraction of an experimental result. Articles may be selected on the grounds that they are interesting or highly promising, not merely because they seem reliable.

arXiv is the oldest and most popular e-print server for scientific publications. arXiv is owned by Cornell University and funded, in part, by the National Science Foundation. Although arXiv papers do not necessarily undergo peer review prior to publication, arXiv exercises several mechanisms of editorial control. Publishing at arXiv requires authors to obtain endorsements for the topic areas in which they publish. This ensures that authors have an appropriate background and that the paper is appropriate for the topic area. Papers which appear unscholarly are removed from arXiv. Papers which are inappropriate for a subject area are removed or reclassified. In general arXiv is more selective than other open-access sites such as philica.com.

Publication at arXiv does not necessarily ensure the same level of quality as publication venues which require prior peer review. Researchers may publish on arXiv for different reasons: to establish priority in a competitive field, to make available newly developed methods to the scientific community while the publication is undergoing peer-review.

A number of questions should be considered when considering the reliability of an arXiv e-print:

1. Has the paper been accepted for publication in a peer reviewed journal?

2. Has the paper been cited in peer reviewed journals by other papers?

3. What are the qualifications of the paper’s authors? Do the authors possess degrees in relevant fields? Have they published peer reviewed papers in the field? Do their institutional affiliations lend confidence to their work?

4. Does the e-print itself cite papers showing consistent results? Confidence in an e-print is significantly enhanced if a number of peer reviewed articles are in agreement with its findings.

There are a growing number of sources on the web that publish e-prints of articles and conference abstracts. Websites exercise various levels of editorial control. Unless the source exercises editorial control, e-prints and conference abstracts should be considered to be self-published. The above questions can be used to consider the reliability of self-published scientific material. See the policy on self-published sources at WP:SPS. Many of them are also primary sources, which should be treated with caution. See the policy advice on primary sources.

There are techniques that scientists use to prevent common errors, and to help others replicate results. Some characteristics to look for are experimental controls (such as placebo controls or heretofore best-treatment controls) and double-blind assignment of treatments to experimental units (e.g. patients for medical studies); additionally triple-blind measurement of outcomes improves quality.

Reliable studies don't just present conclusions. Details about the design and implementation of the experiment should be available. Summary measurements should be available. Unless privacy concerns prohibit their disclosure, raw data should be made available in a supplementary report or by request.

There are several legal structures for the creation, validation and enforcement of law and the resulting corpus of law is only valid in the jurisdiction of origin. The opinion of experts within the jurisdiction is therefore preferred, in general, to that of outside commentators. Legal material may also be divided into the legal statement itself, material to support or inform that legal statement and judgments of opinion when applying the law in practice.

When discussing legal texts, it is more reliable to quote from the text, or from appropriately qualified jurists or textbooks than from newspaper reporting. Some nations allow public-domain copying of administration documents, such as in Italy, so large sections can be quoted (without copyright restrictions) or primary texts could be copied to Wikisource.

Material published by a trading organisation is a view of how that organisation looks on itself however it will also have a marketing component and may lack neutrality. If this material is used it should carry a caveat to indicate this risk and should be corroborated with independent reporting if possible. The accounts and notes to the accounts for all publicly listed companies are required to have been independently audited and will contain a statement to that effect, possibly with caveats considered significant by the auditors. Smaller companies and partnerships which are not publicly listed may have audited accounts. These accounts should provide a reliable view as to the financial health of the organisation however this is subject to the accounting principles applied, which should be identified in the notes. Due to the specialised skills required to assess financial health this material should not be used in isolation, a more acceptable judgement of the organisation can be obtained from investment analysis conducted in some segments of the business press, stock markets and significant investment vehicles. It should be noted that in some cases these assessments may be confidential.

Any judgements in Wikipedia with regard to trading organisations should be explicitly referenced and caveated with comments as to the reliability and range of sources used.

Crime statistics may detail crime reported to the police, crime recorded by the police (crime reports may not be recorded at the discretion of police), or crime experienced by the public – whether reported or not (determined by survey). Different police departments will have different rules for how to categorise and whether to record crime. This varies from country to country.

Where multiple crimes are committed in a single event, it is common to record only the most serious offense. In some countries, Police department districts may differ from municipal boundaries. Police crime recording rules are often revised leading to a problem in comparing crime rates from one year to another.

As a result, use of summarised crime statistics from raw data to indicate the criminality of a certain area in comparison with others or the prevalence of a certain type of crime constitutes original research. Editors should use reliable secondary sources for commentary on trends in the criminality or peacefulness of a district.

Articles related to popular culture and fiction must be backed up by reliable sources like all other articles. However, due to the subject matter, many may not be discussed in the same academic contexts as science, law, philosophy and so on; it is common that plot analysis and criticism, for instance, may only be found in what would otherwise be considered unreliable sources. Personal websites, wikis, and posts on bulletin boards, Usenet and blogs should still not be used as secondary sources. When a substantial body of material is available, the best material available is acceptable, especially when comments on its reliability are included.

In significant world religious denominations with organized academies or recognized theological experts in religious doctrine and scholarship, the proceedings of official religious bodies and the journals or publications of recognized and well-regarded religious academies and experts can be considered reliable sources for religious doctrine and views where such views represent significant viewpoints on an article subject. Ordination alone does not generally ensure religious expertise or reliability. Absent evidence of stature or a reputation for expertise in a leading, important religious denomination or community, the view of an individual minister or theologian is ordinarily not reliable for representing religious views.

Secondary sources are not necessarily from recent years – or even centuries. The sacred or original text(s) of the religion will always be primary sources, but any other acceptable source may be a secondary source in some articles. For example, the works of Thomas Aquinas are secondary sources for a Roman Catholic perspective on many topics, but are primary sources for Thomas Aquinas or Summa Theologica.

• Material from bulletin boards and forum sites, Usenet, wikis, blogs and comments associated with blog entries should not normally be used as sources. These media do not have adequate levels of editorial oversight or author credibility and lack assured persistence.
  • An Internet forum with identifiable, expert and credible moderators with a declared corrective moderation policy may, exceptionally, be considered reliable for some topics. In this sense, where moderators act as editors to review material and challenge or correct any factual errors, they could have an adequate level of integrity. This exception would only be appropriate to fields that are not well covered by print sources, where experts traditionally publish online.
  • In cases where self-published material has been published by a professional researcher or other expert in the field, a source published in one of these media may be considered reliable in some cases.
• Trivia on sites such as IMDb or FunTrivia should not be used as sources. These media do not have adequate levels of editorial oversight or author credibility and lack assured persistence.
  • One exception being that certain film authorship (screenwriting) credits on IMDb, specifically those which are provided by the Writer's Guild of America, can be considered to be adequately reliable.
• Websites and publications of political parties, religious groups, anti-religious groups, or any other partisan group, may exhibit bias and should be treated with caution. Neither political affiliation nor religious belief stated in these sources are in themselves a reason not to use them, as these websites can be used to present the viewpoints of these groups, if properly attributed. Such sources should be presented alongside references from other sources in order to maintain a neutral point of view.
• Websites and publications of trading companies, organizations and charities are a marketing communication channel and should be treated with caution. These media can be used for primary data about the organization's view of itself and may have clear bias related to commercial interests. Effort should be made to corroborate the reference with an independent source to maintain a neutral point of view.
  • Accounts and Notes to the Accounts in an annual report, which have been independently audited, can be considered secondary sources about the organization, and have some level of reliability. The process of audit provides a degree of editorial oversight although the statement by the auditors may contain caveats which should be borne in mind when using the material. Accounts should identify the accounting policies used which will increase the perceived level of reliability.
• Widely acknowledged extremist organizations or individuals, whether of a political, religious, racist, or other character, should be used only as primary sources; that is, they should only be used in articles about those organizations or individuals and their activities. Even then they should be used with caution.
• Usenet is typically only a reliable source with respect to specific FAQs, specific usenet administration groups (when discussing usenet administration), or when discussing persons who have become well known through their usenet activity, such as Kibo.
• Documents released by the IETF RFC Editor (link) are canonical on the subject of Internet and Internet protocols. (see: RFC 2026 )
• Peer-reviewed journals are sometimes published only in electronic format, such as the Public Library of Science; articles published in these electronic journals can be considered reliable as in other peer-reviewed journals. The reliability depends, as always, on the journal: PLoS Biology and PLoS Medicine are perhaps the two leading ones.
• Online material should normally be available in archived form. If they do not have adequate levels of database documentation, the reliability may be questioned.

• Wikipedia:Advanced source searching
• Wikipedia:Manual of Style (Islam-related articles)#References
• WP:PAYWALL — Editors need not limit themselves to only free sources
• WP:Suggested sources – List of specific reliable sources
• Wikipedia:Reliable sources/Perennial sources - List of commonly discussed sources
• WP:UPSD, a user script which highlights potentially unreliable citations.