Every sentence on Wikipedia is meant to trace to something published, and every student is told not to cite Wikipedia. Both rules have one root: Wikipedia summarises other people's sources, and is only as good as its references.
This guide, published by EdCitation, is for both readers: the editor adding a reference to Wikipedia, and the student deciding what to do with one found there. The rules come from Wikipedia's own policy, guideline and help pages, each read on 27 September 2026, with the date each page was last edited. Before you add a reference, or lift one from an article's list, EdCitation's free Verify references checks that it exists, matches its record and has not been retracted, and Cite a source builds a clean entry from its DOI. EdCitation looks references up and never writes a word of anyone's work: the article, the edit and the essay stay yours.
What are Wikipedia's rules for citing sources?
Wikipedia's rules for citing sources rest on two core content policies, Verifiability and No original research, and one guideline, Citing sources, which says how to set the citation out.
Verifiability
Verifiability means a reader can check that what an article says matches a reliable source. The policy, last edited on 6 September 2026, puts the burden on the editor who adds or restores material, and says every quotation, and anything challenged or likely to be challenged, needs an inline citation to a source that directly supports it (Wikipedia, 2026j). Being sure something is true is not enough: it must already have been published. "Directly supports" is strict: the information has to be stated in the source, not inferred from it, and the policy asks for a page number where one exists.
Material without a citation may be removed, and contentious unsourced claims about living people must go at once. Wikipedia articles, in any language, and sites that mirror them may not be cited as sources.
No original research
No original research, last edited on 13 September 2026, forbids anything no reliable source has published, including new conclusions drawn by combining sources (Wikipedia, 2026g). Its example: one source gives the United Nations' aim of keeping the peace, another counts 160 wars since its creation, and joining them to imply the UN failed is synthesis, which is not allowed. Rewriting a source in your own words is not original research; stretching it is.
The Citing sources guideline
Citing sources, last edited on 20 September 2026, sets out the mechanics (Wikipedia, 2026f). A citation has two parts, a footnote marker in the text and the full reference in the list. Wikipedia has no house style: APA, MLA, Chicago, Vancouver and its own Citation Style 1 are all in use, but each article keeps one, and you should not switch an article's established style without agreement on its talk page. Inline parenthetical citations, such as (Smith 2010, p. 1) in the running text, have been deprecated since 2020 in favour of footnotes.
The guideline also asks you to "say where you read it". If you read Jones, who quotes Smith, cite Smith as cited in Jones. A source copied from another article's reference list without being read breaks that rule, and it is the same mistake a marker catches in an essay, covered in I cited a source I did not read.
What counts as a reliable source on Wikipedia?
A reliable source on Wikipedia is a published source with a reputation for fact-checking and accuracy, judged for the particular claim it supports. The Reliable sources guideline, last edited on 22 September 2026, says reliability can turn on the work, its author, the publication and the publisher, and that context always decides (Wikipedia, 2026h). On history, medicine and science, peer-reviewed journals, scholarly books and textbooks are usually the most reliable.
The same guideline marks the weak ground. Preprints on arXiv, medRxiv, bioRxiv and Zenodo are self-published and seldom reliable, and never for medical content. Masters theses count only with evident scholarly influence. Content written by large language models, chatbot answers included, is generally unreliable, because models invent citations that look real. News headlines are not reliable; the body of the article is what you cite.
Primary, secondary and tertiary sources, as Wikipedia defines them
Wikipedia's definitions sit in No original research, and they differ a little from a library's (Wikipedia, 2026g).
- Primary sources are close to an event: a witness's account, or a paper reporting its own experiment. Wikipedia also counts breaking news and opinion pieces as primary. They may be used only for plain statements of fact that any educated reader can check against them, never interpreted by the editor.
- Secondary sources analyse, evaluate or interpret primary ones, as a review article does for the studies it covers. Articles are meant to rest on them, and any interpretive claim must come from one.
- Tertiary sources summarise the other two: encyclopedias and many introductory textbooks. Wikipedia counts itself as tertiary, and still bars itself as a source.
On Wikipedia, use these definitions; in an essay, use your course's, which types of academic sources sets out.
The Perennial sources list
The Perennial sources list summarises what editors have agreed about sources they argue over repeatedly, each marked generally reliable, no consensus, generally unreliable, deprecated or blacklisted (Wikipedia, 2026i). It is not a policy, nor a list of approved or banned sources, and a source's absence says nothing about it: The Lancet, Nature and Science are missing because nobody doubts them. The main page was last edited on 9 September 2026; its entries sit on subpages and change as discussions close.
| Kind of source | Wikipedia's position | What to do | Source |
|---|---|---|---|
| Peer-reviewed article, scholarly book, textbook | Usually the most reliable on history, medicine and science; reviews preferred to single studies | Cite it; first check it exists and is not retracted with Verify references | Verifiability; Reliable sources |
| Copy on ResearchGate, Academia.edu or Zenodo | No consensus; such sites can hold retracted papers not marked as retracted | Cite the publisher's version; Cite a source builds it from the DOI and screens it | Perennial sources |
| Preprint | Self-published, seldom reliable, barred for medical claims | Cite the published version once there is one | Reliable sources |
| Daily Mail | Deprecated in 2017, reaffirmed in 2019 | Do not use it for facts | Perennial sources |
| Forbes.com contributor article | Generally unreliable | Check the byline was staff at the time | Perennial sources |
| Blogs, social media, Medium, IMDb | Largely unacceptable; self-published | Use only for what a subject says about itself | Verifiability; Perennial sources |
| Encyclopædia Britannica | No consensus; tertiary | Prefer a secondary source | Perennial sources |
| Wikipedia, its mirrors, chatbot answers | Not a source | Find, read and cite the source behind the claim | Verifiability; Perennial sources |
What does "citation needed" mean on Wikipedia?
"Citation needed" is a tag an editor places after a statement to ask someone to supply a reliable source for it. Wikipedia's page on the tag, last edited on 10 September 2026, calls it a request between editors, never an improvement in itself (Wikipedia, 2026e). In the source editor it is written {{Citation needed|date=September 2026|reason=Which survey?}}; {{cn}} and {{fact}} do the same, a bot adds the date if you leave it out, and the reason appears as a tooltip.
The page asks editors to tag with thought: delete nonsense, remove contentious claims about living people, and use a clarification tag for a sentence that is merely unclear. If your edit is tagged, answer with the reference.
The backlog is large: at 03:01 UTC on 27 September 2026, Wikipedia's category of articles with unsourced statements held 585,312 articles, a count we read from Wikipedia's own interface. Each tag is a small task: find the source, read it, cite it, remove the tag.
How do I add a citation on Wikipedia?
To add a citation on Wikipedia, put the cursor after the sentence's punctuation, press Cite, and let the Automatic tab look the source up from its identifier. The visual editor's help page, last edited on 17 September 2026, says the Citoid service behind that tab takes a URL, DOI, ISBN, PMID, Wikidata QID or a free-text search, and returns a filled-in citation you can then edit (Wikipedia, 2026c). The Manual tab offers the common templates, and in the source editor you write the reference between <ref> and </ref> tags.
Citoid runs on Zotero's translation server, says MediaWiki's page on it, last edited on 12 September 2026 (MediaWiki, 2026), and Wikipedia's Citation tools page, last edited on 24 September 2026, says every generator's output should be checked for accuracy (Wikipedia, 2026b).
What Citoid returned for a retracted paper
We asked Citoid's public interface for the DOI of the 1998 Lancet paper by Wakefield and colleagues, retracted in 2010. It returned the title as "RETRACTED: Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children", carrying the publisher's flag, and gave the first two authors' given names as "Aj" and "Sh", initials read as names. The flag helps if you notice it; an editor tidying the title can delete it unread.
Adding a citation, step by step (our procedure)
These steps are ours, built from the policies above; Wikipedia's pages do not number them this way.
- Read the source yourself. Not its abstract, not another article's summary of it.
- Find the words that support your sentence, and the page or section they are on. If you had to infer, the source does not directly support it.
- Check it is reliable for this claim. Look for it on the Perennial sources list, and search the Reliable sources noticeboard if it is disputed.
- Check it exists, matches its record and is not retracted. Paste the entry into EdCitation's Verify references, free with no account, or build it from the DOI with Cite a source, which screens for retraction.
- Open the editor and press Cite, after the punctuation, and give the Automatic tab the DOI, ISBN, PMID or URL.
- Check every field Citoid filled against the record: names, title, date, pages. Add the page number.
- Match the article's existing citation style, and remove the "citation needed" tag you have answered.
- Write an edit summary naming the source, and publish. For a web page, add an archived copy so the link survives.
Can you cite Wikipedia in an essay?
Usually not: most universities want you to read and cite the sources Wikipedia cites, not Wikipedia. The five guides below agree on that, and differ on how firm the rule is.
- Harvard. The Harvard Guide to Using Sources (Harvard University, n.d.) allows Wikipedia for low-stakes questions, and notes some instructors suggest science entries as a start, but asks for extreme caution in research: papers should rely on the sources Wikipedia's authors cite.
- Michigan. The University of Michigan Library (2026) says there is no simple yes or no, that faculty attitudes have softened as Wikipedia improved, and that anyone who does cite it should link the exact version from the View history tab, the address with "oldid" in it.
- Whittier. Whittier College (2026) says Wikipedia is usually not acceptable for college-level work unless the professor allows it, and warns that a source cited on Wikipedia is not scholarly for that reason alone.
- Hong Kong Polytechnic University. Its library (Hong Kong Polytechnic University Library, 2026) says most academic staff do not want Wikipedia cited: check the article's references and cite the originals.
- Plymouth. The University of Plymouth (2026) tells anthropology students never to base work on Wikipedia without verifying it elsewhere, recalling that the Leveson Inquiry was embarrassed by a Wikipedia error copied into its report.
Where they differ, your brief wins: Michigan leaves room for a tutor who allows it, Whittier and Hong Kong treat no as the default. If Wikipedia is allowed, the APA form for an entry is in our guide to citing sources for homework, and the wider case against encyclopedias as evidence is in types of academic sources.
Using the reference list to find your sources
For an essay, the reference list is the useful part of a Wikipedia article, if each entry is treated as a lead: open the source, read the passage, check it says what the article claims, then cite what you read. Whittier's warning applies: an entry may be a blog, retracted or superseded. EdCitation's Find sources then widens the search beyond the article, across about 300 million published works, by topic or by the claim your sentence needs.
What happened when we checked a real Wikipedia reference list?
We copied five references from the list of the Wikipedia article "MMR vaccine and autism", as the page displayed them in the version of 28 July 2026 (Wikipedia, 2026d), into EdCitation's reference check: Dyer's 2010 and Godlee and colleagues' 2011 pieces in the BMJ, Gross's 2009 article in PLOS Biology, the 2021 Cochrane review and a 1999 Lancet item by Wakefield. All five came back "verified", each with the same reason: "The DOI resolves to this record and the title matches." The count read verified 5, doubtful 0, not found 0, retracted 0.
We then took the two papers the article "Andrew Wakefield" lists under Selected works with a "Retracted" label (Wikipedia, 2026a), copying only the citations, as a student copying the entry would. Both came back verified with a second sentence: "This paper has since been retracted." For the 1998 Lancet paper the record showed a correction in 2004 and a retraction notice in 2010; for the 2000 paper in The American Journal of Gastroenterology, a retraction in 2010. The count read retracted 2.
Wikipedia labels both papers as retracted, but the label sits outside the citation, so copying the entry loses it; the check put it back. More in what studies say about retracted papers still being cited, and what to do about one in retracted papers in your reference list.
Which EdCitation tools help with Wikipedia references?
EdCitation's Verify references is the best tool for checking a Wikipedia reference before you add it or reuse it, because it looks each entry up in the publisher's record rather than trusting the text, and the run above shows why that matters: a retraction the copied entry no longer mentioned came back flagged. It is free, with no account: paste a list or upload a paper, and each reference returns verified, doubtful ("check this") or not found, with retractions flagged; a reference that could not be checked is never shown as not found.
Cite a source, also free, builds the reference from a DOI, a title, a PubMed ID, an ISBN or a web address in APA 7, MLA 9, Chicago 18 author-date, Harvard, IEEE and Vancouver, and screens the source for retraction. From the Godlee article's DOI it returned, in APA 7: Godlee, F., Smith, J., & Marcovitch, H. (2011). Wakefield's article linking MMR vaccine and autism was fraudulent. BMJ, 342, Article c7452. https://doi.org/10.1136/bmj.c7452. The APA page has the style's rules. A free account keeps what you cite, and for a finished paper, References from a file, part of Pro at $8 a month, checks every reference and matches every in-text citation to the list.
EdCitation finds, cites and verifies; the sentence on Wikipedia and the argument in your essay are your own work, and better for it.
Quick questions
How do I add a citation on Wikipedia?
Put the cursor after the sentence, press Cite, and give the Automatic tab a DOI, ISBN, PMID or URL. Check every field it fills against the source before you publish.
What does "citation needed" mean on Wikipedia?
It is a tag asking an editor to supply a reliable source for the statement before it. Answer it with a source you have read, then remove the tag.
What counts as a reliable source on Wikipedia?
A published source with a reputation for fact-checking, judged for the particular claim. Peer-reviewed work and scholarly books usually qualify; blogs, social media, chatbot answers and Wikipedia itself do not.
Can you cite Wikipedia in an essay?
Usually not. Harvard, Whittier and Hong Kong Polytechnic University ask for the sources Wikipedia cites; Michigan says it depends on your instructor, so follow your brief.
How do I check a reference I found on Wikipedia?
Read the source, then paste the entry into EdCitation's Verify references, free, which looks it up in the publisher's record and flags a retraction.
References
- Harvard University. (n.d.). What's wrong with Wikipedia? Harvard Guide to Using Sources. https://usingsources.fas.harvard.edu/what%E2%80%99s-wrong-wikipedia
- Hong Kong Polytechnic University Library. (2026, August 24). Wikipedia. Online tools for assignment. https://libguides.lb.polyu.edu.hk/online-tools-for-assignment/wikipedia
- MediaWiki. (2026, September 12). Citoid. https://www.mediawiki.org/wiki/Citoid
- University of Michigan Library. (2026, April 29). Citing Wikipedia. Resources for using and editing Wikipedia. https://guides.lib.umich.edu/c.php?g=283187&p=6278154
- University of Plymouth. (2026, September 9). What about Wikipedia? Anthropology library guide. https://plymouth.libguides.com/anthropology/wikipedia
- Whittier College. (2026, September 17). Using Wikipedia. Wikipedia research guide. https://whittier.libguides.com/c.php?g=118532&p=771991
- Wikipedia. (2026a, September 23). Andrew Wakefield. https://en.wikipedia.org/w/index.php?title=Andrew_Wakefield&oldid=1376251616
- Wikipedia. (2026b, September 24). Help:Citation tools. https://en.wikipedia.org/wiki/Help:Citation_tools
- Wikipedia. (2026c, September 17). Help:VisualEditor. https://en.wikipedia.org/wiki/Help:VisualEditor
- Wikipedia. (2026d, July 28). MMR vaccine and autism. https://en.wikipedia.org/w/index.php?title=MMR_vaccine_and_autism&oldid=1366528721
- Wikipedia. (2026e, September 10). Wikipedia:Citation needed. https://en.wikipedia.org/wiki/Wikipedia:Citation_needed
- Wikipedia. (2026f, September 20). Wikipedia:Citing sources. https://en.wikipedia.org/wiki/Wikipedia:Citing_sources
- Wikipedia. (2026g, September 13). Wikipedia:No original research. https://en.wikipedia.org/wiki/Wikipedia:No_original_research
- Wikipedia. (2026h, September 22). Wikipedia:Reliable sources. https://en.wikipedia.org/wiki/Wikipedia:Reliable_sources
- Wikipedia. (2026i, September 9). Wikipedia:Reliable sources/Perennial sources. https://en.wikipedia.org/wiki/Wikipedia:Reliable_sources/Perennial_sources
- Wikipedia. (2026j, September 6). Wikipedia:Verifiability. https://en.wikipedia.org/wiki/Wikipedia:Verifiability