Citation checker
Check that every reference is real, accurate, and correctly formatted.
Results
Your results will appear here, one reference at a time.
How the citation checker works
It works as a reference checker and a source checker. We look up every reference in real databases of published work, so each result comes from the published record, not from an AI guess.
Step 1
Paste or upload
Paste your reference list, works cited or bibliography, or a single citation. On the Full paper tab, paste your whole paper or upload a PDF or Word (.docx) file.
Step 2
We look up each source
We start with the DOI if there is one. Then we search Crossref, OpenAlex and Semantic Scholar for articles, PubMed for medical ones, and Open Library and Google Books for books. For a website, we open the page itself.
Step 3
We compare the details
For articles and books, the title, authors, year, journal, volume, pages and DOI are compared with the published record. For papers with a DOI, we also check whether they have been retracted.
Step 4
We check the formatting
Each reference is compared with a correct version in your style, made by the same engine as our Citation Generator. Choose from APA, MLA, Chicago, Harvard and 10,000+ other styles.
Step 5
We check your in-text citations
On the Full paper tab, we match each in-text citation to your reference list in your browser. Only the reference list is sent to look up your sources, plus the sentences that cite them if you turn on the claim check.
Step 6
Correct and export
Choose Fix or Use this version on the references you want to change, then copy the corrected list into Word or Google Docs, download it as a .docx file, or open it in the Citation Generator.
What each result means
Each reference gets one of the first four results. Retracted is shown on top of the result, so a retracted paper can also say Verified.
Verified
We found the source, and its key details match what you wrote. For a website, that means the page opens and its title fits, so check the author and date yourself. The formatting check may still suggest small fixes.
Details don’t match
The source is real, but something is different: the year, an author’s name, the title, the journal, the volume, the pages, or a DOI that belongs to another paper. We show your reference next to the published record.
Couldn’t find this source
We couldn’t find it in the databases we search. That doesn’t always mean it’s made up: books, reports, very new work and non-English sources are sometimes missing. Choose Look it up in the citation finder to search for it by author, year and title, or choose Search again and add a DOI or link.
Couldn’t check right now
A database didn’t answer in time. It says nothing about whether the source is real. Choose Check again in a moment.
Retracted
The paper has been withdrawn by its journal, usually because of serious errors or misconduct. Don’t cite it as evidence. If you mention it, say that it was retracted.
What we check in your paper
Use the Full paper tab to check citations in your text as well as your reference list. It works with the usual ways of citing: author and year, like (Smith, 2020); author and page, like (Smith 45); numbers, like [1] or ¹; and footnotes. For superscripts and footnotes, upload the Word or PDF file, since a plain paste can lose them.
No matching reference
An in-text citation, such as (Smith, 2020), with no entry in your reference list.
Not cited in your paper
A reference in your list that is never cited in the text.
Year doesn’t match
The year in the text differs from the reference, such as (Smith, 2019) for a reference dated 2020.
Name doesn’t match
An author’s name is spelled differently in the text and in the list, such as (Kahnemann, 2011) for a reference by Kahneman.
Unclear which reference
Two references by the same author in the same year, with no letter (2020a, 2020b) to tell them apart.
Numbered out of order
In numbered styles such as IEEE and Vancouver, references should be numbered in the order they are first cited.
Do your sources support your claims? (beta)
On the Full paper tab, tick “Also check that sources support your claims” before you check, or choose Check claims once your results are in. Our AI model compares each sentence that cites a source with that source’s abstract, then gives one of these results and quotes the abstract sentences behind it. It works for sources with a DOI and an abstract we can find, up to 40 sentences a check. It reads the abstract only, so treat it as a first look, not a final judgment. When the abstract says otherwise or doesn’t address your sentence, choose Find a source for this sentence to search for one in our Citation Finder.
Supports
The abstract states what your sentence says, or clearly implies it.
Partly supports
The abstract backs part of your sentence, but not all of it. For example, your sentence adds a detail the abstract doesn’t give, applies the finding to a wider group than the study looked at, or says one thing causes another when the study only found a link.
Abstract says otherwise
The abstract contradicts your sentence, for example by reporting the opposite result.
Doesn’t address this
The abstract is about something else, which can mean the citation points to the wrong paper.
Can’t tell from the abstract
The abstract is on the right topic but doesn’t say enough to confirm or rule out your point. The full paper may cover it.
Why AI tools invent references
Chatbots write by predicting what text usually comes next. A reference is just more text to them, so when they don’t have a real source to hand, they can produce one that looks right: real-sounding authors, a plausible title, a journal that exists, and a year that fits. Nothing in that process checks whether the paper was ever published.
That is why AI-generated reference lists often mix real and invented sources, and why a real source often appears with the wrong year, pages or DOI. Some tools now search the web before they answer, which helps, but they can still attach the wrong details to a real paper.
The most reliable test is to look each source up in a database of published work, which is what a citation checker does.
How to spot a fake reference
These signs suggest a reference may be invented or mixed up, and they’re worth knowing whenever you use an AI tool. The checker looks for the first four for you.
The DOI opens a different paper
Paste the DOI into doi.org. If it leads to another title, the reference was probably stitched together from parts.
The title can’t be found
Search for the exact title in quotation marks. A real journal article almost always turns up.
Real authors, wrong paper
The authors exist and work in the field, but none of their publications has this title or year.
The details don’t fit the journal
The volume or page numbers don’t match what the journal actually published.
The title echoes your question
The title repeats the exact wording of your essay question or topic. Real papers rarely do.
Common citation errors and how to fix them
Wrong year
With the error
Kahneman, D., & Tversky, A. (1976). Prospect theory: An analysis of decision under risk. Econometrica, 47(2).
Fixed
Kahneman, D., & Tversky, A. (1979). Prospect theory: An analysis of decision under risk. Econometrica, 47(2).
Use the year the article was published. For a book, use the year of the edition you read. The checker shows the year from the published record.
A DOI that belongs to another paper
With the error
LeCun, Y., Bengio, Y., & Hinton, G. (2015). Deep learning. Nature, 521(7553). https://doi.org/10.1038/s41586-021-03819-2
Fixed
LeCun, Y., Bengio, Y., & Hinton, G. (2015). Deep learning. Nature, 521(7553). https://doi.org/10.1038/nature14539
Copy the DOI from the article’s own page. A DOI for a different paper is a common sign of an AI-written reference.
Title in title case
With the error
Ryan, R. M., & Deci, E. L. (2000). Self-Determination Theory and the Facilitation of Intrinsic Motivation, Social Development, and Well-Being. American Psychologist, 55(1).
Fixed
Ryan, R. M., & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. American Psychologist, 55(1).
APA uses sentence case for article and book titles and title case for journal names.
Misspelled author
With the error
Kahnemann, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.
Fixed
Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.
Check names against the source. A slip in the list usually appears in your in-text citations too.
In-text citation that doesn’t match
With the error
(Harris & Liu, 2019) for a reference dated 2020
Fixed
(Harris & Liu, 2020)
The author and year in the text must match the reference exactly, or readers can’t find the source.
Frequently asked questions
Is this citation checker free?
Yes. It’s a free citation checker, and you don’t need to sign up. You can check 50 references at a time, 30 times a day, and use the claim check (beta) 5 times a day. A longer list is checked 50 at a time, and each round counts as one check. Each browser has its own checks, so classmates on a school network don’t use up yours, though a very busy network can reach a daily limit of its own. They reset every day.
How do I check my citations?
Paste your reference list into the Reference list tab above and choose Check references. To check the citations in your text too, use the Full paper tab: paste your paper or upload a PDF or Word file, then choose Check paper. Results appear one reference at a time.
Does “Couldn’t find this source” mean a source is fake?
Not always. Books, reports, theses, very new work and non-English sources are sometimes missing from the databases we search. Choose Look it up in the citation finder, look up the exact title in Google Scholar or your library search, or choose Search again and add the DOI or a link. If you can’t find the source anywhere, don’t use it until you’ve confirmed it exists.
How does it check if a source is real?
It looks each reference up in Crossref, OpenAlex, Semantic Scholar, PubMed, Open Library and Google Books, or opens the page for a website, then compares your details with the published record. We use AI only to split up messy lists, never to decide whether a source is real. The optional claim check is the one place our AI model gives a result.
Which citation styles are supported?
It reads APA, MLA, Chicago, Harvard, IEEE and Vancouver references on its own, so it works as an APA or MLA citation checker without you saying which style you used. For the formatting check, choose your style from the same 10,000+ styles as our Citation Generator.
Does it check in-text citations?
Yes. On the Full paper tab, paste your paper or upload a PDF or Word file. It matches each in-text citation to your reference list and flags missing references, uncited sources, and names or years that don’t match.
Is my paper stored?
Not on our servers, unless you choose Continue in Writing Studio. On the Full paper tab, your paper is read in your browser, and only the reference list is sent to look up each source. If you use the claim check, the sentences that cite a source are sent to the AI model we use, from an outside AI provider, and we don’t store them. We keep only the result and its one-line reason, for up to 30 days, under a scrambled code that can’t be turned back into your text, so a repeat check is faster. If you choose Continue in Writing Studio after a check, we keep your paper for one day so it can open in your account once you sign up or sign in. Your last check, with its text and results, stays in your browser so a reload doesn’t lose it. Choose Clear under the text box to remove it.
How is this different from a citation generator?
A citation generator creates a new citation from a link, DOI or title. A citation checker takes the references you already have and tells you whether each source is real, whether the details are right, and whether the formatting follows your style.
Can it check a reference list from ChatGPT or another AI tool?
Yes. Paste the list and each reference is checked against real databases. References that can’t be found, or whose DOI points to another paper, are the most common signs of invented sources.
Can it tell me if a source is credible?
It checks that a source exists, that your details match the published record, and whether the source was retracted. It doesn’t rate quality. To judge a source yourself, look at where it was published (a peer-reviewed journal or a reputable publisher), how recent it is, and who wrote it.
Does it find retracted papers?
Yes, for papers with a DOI. If Crossref or OpenAlex records a paper as retracted, we mark it Retracted. Sources without a DOI can’t be checked this way, so for an important source, look at the journal’s page too.
What if I cited a preprint?
If it’s an arXiv preprint that has since come out in a journal or conference, we say where and when it was published. Choose Use the published version to put that version in your corrected list. Most instructors prefer the published version, since it has been through peer review.
How long can my paper be?
Free checks cover papers up to 15,000 words, not counting the reference list, and look up 50 references at a time. If your paper has more, choose Check the next under the results to look up the rest. For a longer paper, paste just the reference list in the Reference list tab.
Can it correct my citations?
Yes, for your reference list. For each source we find, it shows what to change and a correctly formatted version in your style. Choose Fix or Use this version to accept it, then copy the corrected list or download it as a .docx file. It doesn’t change the citations in your paper. To fix those too, choose Continue in Writing Studio after a Full paper check: your paper opens as a new document with each matched citation linked to its corrected source, and the reference list writes itself.