Wikipedia articles must not contain original research. On Wikipedia, original research means material—such as facts, allegations, and ideas—for which no reliable, published source exists. This includes any analysis or synthesis of published material that reaches or implies a conclusion not stated by the sources. To demonstrate that you are not adding original research, you must be able to cite reliable, published sources that are directly related to the topic of the article and directly support the material being presented.

The prohibition against original research means that all material added to articles must be verifiable in a reliable, published source, even if not already verified via an inline citation. The verifiability policy says that an inline citation to a reliable source must be provided for all quotations, and for anything challenged or likely to be challenged—but a source must exist even for material that is never challenged. For example, the statement "the capital of France is Paris" does not require a source to be cited, nor is it original research, because it's not something you thought up and it is easily verifiable; therefore, no one is likely to object to it and we know that sources exist for it even if they are not cited. The statement is verifiable, even if not verified.

Despite the need for reliable sources, you must not plagiarize them or violate their copyrights. Rewriting source material in your own words while retaining the substance is not considered original research.

"No original research" (NOR) is one of three core content policies that, along with Neutral point of view and Verifiability, determines the type and quality of material acceptable in articles. Because these policies work in harmony, they should not be interpreted in isolation from one another, and editors should familiarize themselves with all three. For questions about whether any particular edit constitutes original research, see the No original research noticeboard.

This policy does not apply to talk pages and other pages which evaluate article content and sources, such as deletion discussions or policy noticeboards.

Wikipedia is fundamentally built on research that has been collected and organized from reliable sources, as described in content policies such as this one. If no reliable independent sources can be found on a topic, Wikipedia should not have an article about it. If you discover something new, Wikipedia is not the place to announce such a discovery.

The best practice is to research the most reliable sources on the topic and summarize what they say in your own words, with each statement in the article being verifiable in a source that makes that statement explicitly. Source material should be carefully summarized or rephrased without changing its meaning or implication. Take care not to go beyond what the sources express or to use them in ways inconsistent with the intention of the source, such as using material out of context. In short, stick to the sources.

Any material challenged or likely to be challenged must be supported by a reliable source. Material for which no reliable source can be found is considered original research. The only way you can show that your edit is not original research is to cite a reliable published source that contains the same material. Even with well-sourced material, if you use it out of context, or to state or imply a conclusion not directly and explicitly supported by the source, you are engaging in original research; see below.

In general, the most reliable sources are:

• Peer-reviewed journals
• Books published by university presses
• University-level textbooks
• Magazines, journals, and books published by respected publishing houses
• Mainstream newspapers

However, note that higher standards than this are required for medical claims.

As a rule of thumb, the more people engaged in checking facts, analyzing legal issues, and scrutinizing the writing, the more reliable the publication. Self-published material, whether on paper or online, is generally not regarded as reliable. See self-published sources for exceptions.

Information in an article must be verifiable in the references cited. In general, article statements should not rely on unclear or inconsistent passages or on passing comments. Any passages open to multiple interpretations should be precisely cited or avoided. A summary of extensive discussion should reflect the conclusions of the source. Drawing conclusions not evident in the reference is original research regardless of the type of source. References must be cited in context and on topic.

Wikipedia articles should be based on reliable, published secondary sources, and to a lesser extent, on tertiary sources and primary sources. Secondary or tertiary sources are needed to establish the topic's notability and avoid novel interpretations of primary sources. All analyses and interpretive or synthetic claims about primary sources must be referenced to a secondary or tertiary source and must not be an original analysis of the primary-source material by Wikipedia editors.

Appropriate sourcing can be a complicated issue, and these are general rules. Deciding whether primary, secondary, or tertiary sources are appropriate in any given instance is a matter of good editorial judgment and common sense, and should be discussed on article talk pages. A source may be considered primary for one statement but secondary for a different one. Even a given source can contain both primary and secondary source material for one particular statement. For the purposes of this policy, primary, secondary and tertiary sources are defined as follows:

• Primary sources are original materials that are close to an event, and are often accounts written by people who are directly involved. They offer an insider's view of an event, a period of history, a work of art, a political decision, and so on. Primary sources may or may not be independent sources. An account of a traffic incident written by a witness is a primary source of information about the event; similarly, a scientific paper documenting a new experiment conducted by the author is a primary source for the outcome of that experiment. For Wikipedia's purposes, breaking news stories are also considered to be primary sources. Historical documents such as diaries are as well.

  Policy: Unless restricted by another policy,

  1. Primary sources that have been reputably published may be used in Wikipedia, but only with care, because it is easy to misuse them.
  2. Any interpretation of primary source material requires a reliable secondary source for that interpretation. While a primary source is generally the best source for its own contents, even over a summary of the primary source elsewhere, do not put undue weight on its contents.
  3. A primary source may be used on Wikipedia only to make straightforward, descriptive statements of facts that can be verified by any educated person with access to the primary source but without further, specialized knowledge. For example, an article about a musician may cite discographies and track listings published by the record label, and an article about a novel may cite passages to describe the plot, but any interpretation needs a secondary source.
  4. Do not analyze, evaluate, interpret, or synthesize material found in a primary source yourself; instead, refer to reliable secondary sources that do so.
  5. Do not base an entire article on primary sources, and be cautious about basing large passages on them.
  6. Do not add unsourced material from your personal experience, because that would make Wikipedia a primary source of that material.
  7. Use extra caution when handling primary sources about living people; see WP:Biographies of living persons § Avoid misuse of primary sources, which is policy.

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  • WP:SECONDARY
  A secondary source provides thought and reflection based on primary sources, generally at least one step removed from an event. It contains analysis, evaluation, interpretation, or synthesis of the facts, evidence, concepts, and ideas taken from primary sources. Secondary sources are not necessarily independent sources. They rely on primary sources for their material, making analytic or evaluative claims about them. For example, a review article that analyzes research papers in a field is a secondary source for the research. Whether a source is primary or secondary depends on context. A book by a military historian about the Second World War might be a secondary source about the war, but where it includes details of the author's own war experiences, it would be a primary source about those experiences. A book review too can be an opinion, summary, or scholarly review.

  Policy: Wikipedia articles usually rely on material from reliable secondary sources. Articles may make an analytic, evaluative, interpretive, or synthetic claim only if it has been published by a reliable secondary source.

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  • WP:TERTIARY
  Tertiary sources are publications such as encyclopedias and other compendia that summarize, and often quote, primary and secondary sources. Wikipedia is considered to be a tertiary source. Many introductory undergraduate-level textbooks are regarded as tertiary sources because they sum up multiple secondary sources.

  Policy: Reliable tertiary sources can help provide broad summaries of topics that involve many primary and secondary sources and may help evaluate due weight, especially when primary or secondary sources contradict each other. Some tertiary sources are more reliable than others. Within any given tertiary source, some entries may be more reliable than others. Wikipedia articles may not be used as tertiary sources in other Wikipedia articles, but are sometimes used as primary sources in articles about Wikipedia itself (see Category:Wikipedia and Category:WikiProject Wikipedia articles).

Do not combine material from multiple sources to state or imply a conclusion not explicitly stated by any of the sources. Similarly, do not combine different parts of one source to state or imply a conclusion not explicitly stated by the source. If one reliable source says A and another reliable source says B, do not join A and B together to imply a conclusion C not mentioned by either of the sources. This would be improper editorial synthesis of published material to imply a new conclusion, which is original research. "A and B, therefore, C" is acceptable only if a reliable source has published the same argument concerning the topic of the article. If a single source says "A" in one context, and "B" in another, without connecting them, and does not provide an argument of "therefore C", then "therefore C" cannot be used in any article.

Here are two sentences showing simple examples of improper editorial synthesis. Both halves of the first sentence may be reliably sourced but are combined to imply that the UN has failed to maintain world peace. If no reliable source has combined the material in this way, it is original research.

In this second sentence, the opposite is implied using the same material, illustrating how easily such material can be manipulated when the sources are not adhered to:

Here are two paragraphs showing more complex examples of editorial synthesis. They are based on an actual Wikipedia article about a dispute between two authors, here called Smith and Jones. This first paragraph is fine because each of the sentences is carefully sourced, using a source that refers to the same dispute:

This second paragraph demonstrates improper editorial synthesis:

The second paragraph is original research because it expresses a Wikipedia editor's opinion that, given the Harvard manual's definition of plagiarism, Jones did not commit it. Making the second paragraph policy-compliant would require a reliable source specifically commenting on the Smith and Jones dispute and making the same point about the Harvard manual and plagiarism. In other words, that precise analysis must have been published by a reliable source concerning the topic before it can be published on Wikipedia.

Because of copyright laws in several countries, there are relatively few images available for use on Wikipedia. Editors are therefore encouraged to upload their own images, releasing them under appropriate Creative Commons licenses or other free licenses. Original images created by a Wikimedian are not considered original research, so long as they do not illustrate or introduce unpublished ideas or arguments, the core reason behind the "No original research" policy. Image captions are subject to this policy no less than statements in the body of the article.

It is not acceptable for an editor to use photo manipulation to distort the facts or position illustrated by an image. Manipulated images should be prominently noted as such. Any manipulated image where the encyclopedic value is materially affected should be posted to Wikipedia:Files for discussion. Images of living persons must not present the subject in a false or disparaging light.

Faithfully translating sourced material into English, or transcribing spoken words from audio or video sources, is not considered original research. For information on how to handle sources that require translation, see WP:Verifiability § Non-English sources.

Source information does not need to be in prose form: Any form of information, such as maps, charts, graphs, and tables may be used to provide source information. Any straightforward reading of such media is not original research provided that there is consensus among editors that the techniques used are correctly applied and a meaningful reflection of the sources.

Routine calculations do not count as original research, provided there is consensus among editors that the results of the calculations are correct, and a meaningful reflection of the sources. Basic arithmetic, such as adding numbers, converting units, or calculating a person's age, is almost always permissible. See also Category:Conversion templates.

Mathematical literacy may be necessary to follow a "routine" calculation, particularly for articles on mathematics or in the hard sciences. In some cases, editors may show their work in a footnote.

Comparisons of statistics present particular difficulties. Editors should not compare statistics from sources that use different methodologies.

Wikipedia's content is determined by previously published information rather than by the personal beliefs or experiences of its editors. Even if you're sure something is true, it must be verifiable before you can add it. The policy says that all challenged or likely to be challenged material and all quotations need a reliable source; what counts as a reliable source is described at WP:Verifiability § Reliable sources.

The prohibition against original research limits the extent to which editors may present their own points of view in articles. By reinforcing the importance of including verifiable research produced by others, this policy promotes the inclusion of multiple points of view. Consequently, this policy reinforces our neutrality policy. In many cases, there are multiple established views of any given topic. In such cases, no single position, no matter how well researched, is authoritative. It is not the responsibility of any individual editor to research all points of view. But when incorporating research into an article, editors must provide context for this point of view by indicating how prevalent the position is and whether it is held by a majority or minority.

The inclusion of a view that is held by only a tiny minority may constitute original research. Jimbo Wales has said of this:

• If your viewpoint is in the majority, then it should be easy to substantiate it with references to commonly accepted reference texts;
• If your viewpoint is held by a significant minority, then it should be easy to name prominent adherents;
• If your viewpoint is held by an extremely small minority, then—whether it's true or not, whether you can prove it, or not—it doesn't belong in Wikipedia, except perhaps in some ancillary article. Wikipedia is not the place for original research.

• Citing sources
• Conflict of interest § Citing yourself
• No original research examples
• No original research noticeboard—discussions of specific article content suspected of being OR
• Wikipedia is not for things made up one day

• YouTube video demonstrating the dangers of original research