Reference checker and citation checker

Paste your reference list. We find the record each reference describes, through its DOI or, when it has none, by searching Crossref and Open Library. We compare the record's title, first author and year with what you wrote and show it beside your text, with retraction, preprint and citation flags from OpenAlex when the record has a DOI.

How it works

Paste your references
Up to 10 at a time, in any citation style and any common layout: one per line, separated by blank lines, or numbered as 1., [1] or 1). A heading such as References is skipped.
We find each record
For a reference with a DOI, we fetch the record the DOI leads to from OpenAlex, an open catalogue of scholarly works, or from doi.org, which covers DOIs registered with Crossref and DataCite. For a reference without one, we search Crossref and, for a book, Open Library, an open catalogue of books.
Read each row
We compare the record's title, first author and year with your reference and show the record next to it, with any retraction, preprint or citation flags. Each row says what was compared and what was not.

A worked example

Paste these four references, or press Try an example above. The second one is made up: it borrows the DOI of the first.

1. LeCun, Y., Bengio, Y., & Hinton, G. (2015). Deep learning. Nature, 521(7553), 436-444. https://doi.org/10.1038/nature14539
2. Novak, P., & Lindqvist, A. (2015). Neural networks for protein structure prediction. Nature, 521(7553), 436-444. https://doi.org/10.1038/nature14539
3. Kahneman, D. (2011). Thinking, fast and slow. Farrar, Straus and Giroux.
4. World Health Organization. (2023). Depression. https://www.who.int/news-room/fact-sheets/detail/depression

1. Matches a record
2. This DOI belongs to a different paper
3. Book found
4. Website, not checked

The DOI in the second reference leads to the 2015 deep learning review, so its row shows that paper next to the reference you pasted. A working DOI attached to another paper is one of the most common faults in references written by AI chat tools, and one of the hardest to see by eye. The book has no DOI, so we searched for it and found it in Open Library. The last entry is a web page: open the link to check it.

What each result means

Matches a record: A record matches the title, first author and year (a year one off is allowed and noted). We did not check the volume, pages or what the paper says. When the journal is missing from your reference or differs from the record, the row says so.
Close match, details differ: Part of the record shows in your reference, but something does not line up: compare the two before you use it. For a reference without a DOI, it means we found the title but the authors or the year differ, which is also how a made-up reference built on a published title looks.
Book found: Open Library, an open catalogue of books, has a book with this title, first author and year; the year of a later edition counts when Open Library lists it. We did not check the edition, publisher or pages, so compare them with the book you read.
This DOI belongs to a different paper: The DOI leads to the record of another work, shown next to your reference. Either the DOI was copied from the wrong entry, or the reference does not describe a published paper. Find the paper itself before you cite it.
Record found, nothing to compare: A record exists for this DOI, but the reference has no title to compare it with, for example a bare DOI or a link. Check that the record shown is the paper you mean, and add its title to the reference.
No record for this DOI: Neither OpenAlex nor doi.org knows this DOI. It may have a typo, or the reference may not describe a published paper. Copy the DOI again from the paper's own page.
No matching record found: Neither Crossref nor Open Library has a record that matches the reference. It may be a report, a thesis or very new, or it may not describe a published work: check it by hand.
DOI from an agency we cannot read yet: The DOI is registered with an agency other than Crossref or DataCite, so we cannot read its record yet. Many Japanese, Korean and Italian DOIs are like this. Check this reference by hand.
No DOI: not checked in this version: This reference has no DOI and was not searched this time. Check it by hand, or try again later.
Website, not checked: The reference points to a web page, not a DOI. Open the link and make sure the page is still there and still says what you cite.
Could not check right now: A lookup failed or did not answer in time. This says nothing about your reference: try again in a minute.
Retracted: Marked as retracted in OpenAlex. A retracted paper should not be cited as support for a claim; if you discuss it, say that it was retracted. When a checked row has no such mark, it says: No retraction notice in OpenAlex today. Notices can take weeks to appear.
Preprint: Not peer reviewed yet. Many fields cite preprints, but check whether a reviewed version has appeared since, and cite that one if it has.
Fewer than 5 citations: Fewer than 5 citations in OpenAlex, at least 3 years after publication. Common for niche, regional or non-English work; not a judgement of quality.
Flags not checked: The record has no DOI, or OpenAlex has no record of it or did not answer, so we could not look for a retraction notice, a preprint or the citation count. The status of the row still stands.

How well it works

We tested the checker on 67 references we had set aside: 36 references to published papers and 31 made-up ones (October 2026). All 36 published references matched their record, and none of the 31 made-up references did. The published references were formatted from the same records they were checked against, so references copied by hand will match less often; a made-up reference can still come back as a close match, which is why every row shows the record next to your text.

We also tested references without a DOI, on 320 more references we had set aside: 150 references to published works and 170 made-up ones (October 2026). 134 of the 150 were found or came back as a close match, and none of the 170 made-up references matched a record or a book. The made-up ones include references written by an AI model in the style chatbots use when they make up citations, published titles with the wrong authors, titles with a word or two changed, and made-up books; 26 of them came back as a close match, which is why every row shows the record next to your text. Each published reference in the test has a record in Crossref or Open Library and was formatted from it, so references copied by hand will be found less often, and reports, theses and very new papers, which often have no record anywhere, come back as not found.

What a match tells you, and what it does not

A match means that a record with the same title, first author and year as your reference exists: the record the DOI leads to or, for a reference without a DOI, one our search found. It does not mean that the paper says what you cite it for, and it does not check the volume or pages; a missing or different journal is only noted.

Read the paper, or at least its abstract, before you rely on it. A close match deserves a second look: sometimes the reference is right and the record carries a different year, sometimes a detail was copied wrongly.

Why references go wrong

Most mistakes are small: the year of the online version instead of the print one, a DOI copied from the neighbouring entry, a subtitle dropped, an author's name misspelt. Reference managers make fewer of them, but they copy whatever the record says.

AI chat tools add a bigger problem: references that look complete but describe no published paper, often with a working DOI that belongs to another work. Showing the record next to your text makes both kinds easy to spot.

Checking the rest by hand

For a reference without a DOI, search for its exact title in your library catalogue or on the publisher's site. A book should turn up with the same title, author, edition and year; a report should be on the website of the organisation that published it.

For a web page, open the link. If it is gone, look for an archived copy and cite the date you read it, as most styles ask.

Questions

Is this reference checker free?

Yes. You can check up to 10 references at a time and run 5 checks a day without an account. Everyone on one network, such as a school or a library, shares those 5 checks. The limit resets at midnight UTC.

Which references can it check?

References in any citation style. With a DOI, which can be bare, start with doi: or be a full doi.org link, we look up the record it leads to. Without a DOI, we search for the reference in Crossref and, for a book, in Open Library. Web pages are listed as not checked: open the link to check them.

What if a reference has no DOI?

We search Crossref for it and, when it looks like a book, Open Library. When a record has the same title, first author and year, the row shows it and says it was found by searching. Reports, theses and very new papers often have no record anywhere, so a reference we cannot find is not always wrong: check it by hand.

Does a match mean the reference is correct?

It means that a record with the same title, first author and year exists. We do not check the volume, pages or what the paper says, and a missing or different journal is only noted, so read the source before you rely on it.

Can it catch references made up by AI?

It catches the most common problem: a DOI that leads to a different paper, or to no record at all. It cannot tell who wrote a reference, and a made-up reference can still come back as a close match, so read every row next to its record.

Why is a reference I copied from the paper only a close match?

Usually one detail differs: the record lists another first author, the title has extra words, or the year is more than one off, which happens when a paper appeared online long before print. Compare the two and keep what the paper itself says.

Do you keep the references I paste?

No. The references go to our server, which looks for a DOI in each one and looks that DOI up in OpenAlex and at doi.org; only the DOIs are sent to those services. For a reference without a DOI, part of its text (up to 300 characters, without any DOI or web address) goes to Crossref's search and, when it looks like a book, the first author's family name and the main title (or the ISBN) go to Open Library; nothing else about you is sent. Nothing you paste is saved or linked to you. We count how many checks each visitor makes in a day, using a key that cannot be turned back into an address and that changes whenever our service restarts.

Where do the records and flags come from?

From OpenAlex, an open catalogue of scholarly works, and from doi.org, which hands the request on to Crossref or DataCite. A reference without a DOI is searched in Crossref and, for a book, in Open Library, an open catalogue of books run by the Internet Archive. The retraction, preprint and citation flags come from OpenAlex, for records with a DOI.

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Reference checker and citation checker

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