How to Cite arXiv Preprints in APA 7, MLA 9, Chicago

A preprint is a research article posted to a public repository (arXiv, bioRxiv, medRxiv, SSRN, ChemRxiv, OSF Preprints, Research Square, etc.) before it has completed peer review and been published in a journal. During the COVID-19 pandemic, preprints became central to how biomedical research was communicated. They continue to be common in physics, computer science, economics, and quantitative biology where the time cost of peer review can outpace the field.

Cite a preprint when (a) the work has not yet been published in a peer-reviewed venue, (b) the preprint contains findings not present in a later published version, or (c) your discipline accepts preprints as legitimate scholarly sources. Always prefer the peer-reviewed version when it exists and matches the claim you are citing — most styles require switching to the published form once it becomes available.

APA 7 treats preprints as a distinct source type. The template: Author, A. A. (Year). Title of preprint. Preprint Repository Name. https://doi.org/xxxxx

Vaswani, A., Shazeer, N., Parmar, N., Uszkoreit, J., Jones, L., Gomez, A. N., Kaiser, Ł., & Polosukhin, I. (2017). Attention is all you need. arXiv. https://doi.org/10.48550/arXiv.1706.03762

Lastname, A. B., & Lastname, C. D. (2024). Title of biological preprint. bioRxiv. https://doi.org/10.1101/2024.01.01.000000

• Repository name replaces the "Publisher" slot — use the official name (arXiv, bioRxiv, medRxiv, SSRN, OSF Preprints)
• Use the DOI when assigned — arXiv, bioRxiv, and medRxiv all issue DOIs
• Do not italicize the repository name
• Label as "Preprint" in brackets only if confusion with a published work is possible

MLA 9 uses container-based citation. The repository is the container. Template: Author Last, First. "Title of Preprint." Repository Name, Day Month Year, URL.

Lastname, Firstname. "Title of the Preprint Paper." arXiv, 3 Jan. 2024, arxiv.org/abs/2401.00001.

• MLA 9 recommends a DOI when available; the arxiv.org/abs/ID URL is acceptable if the DOI is not listed on the preprint page
• The day-month-year format is the MLA standard for dates
• Title in quotation marks, not italics (preprints are treated like articles)

Chicago author-date format: Last name, First name. Year. "Title of Preprint." Preprint, submitted Month Day. URL.

Lastname, Firstname. 2024. "Title of the Preprint." Preprint, submitted January 3. https://arxiv.org/abs/2401.00001.

Firstname Lastname, "Title of the Preprint" (preprint, submitted January 3, 2024), https://arxiv.org/abs/2401.00001.

The bibliography entry follows the same structure as author-date with the author inverted.

Vancouver treats preprints as a distinct publication type for biomedical research. Template: Author AA, Author BB. Title of preprint. Repository [Preprint]. Year Month Day [cited Year Month Day]. Available from: URL

Lastname A, Lastname B. Title of medical preprint. bioRxiv [Preprint]. 2024 Jan 3 [cited 2024 Mar 15]. Available from: https://doi.org/10.1101/2024.01.01.000000

• The [Preprint] tag in square brackets after the repository name is a Vancouver convention
• Include access date [cited…] when citing the live URL rather than the DOI
• If the preprint has been superseded by a published version, cite the published version and add "Previously available as preprint" as a note

Lastname, A. B. (2024) 'Title of the preprint', arXiv [Preprint], 2401.00001. Available at: https://arxiv.org/abs/2401.00001 (Accessed: 15 March 2024).

Harvard style mirrors its approach to unpublished or grey literature — the repository plays the role of publisher, the version is flagged "[Preprint]", and an access date is included for URL-only sources.

Once a peer-reviewed version appears, switch your citation to the published form unless you specifically need a claim or figure that only appears in the preprint. If you cite both, make the distinction explicit: "(Smith et al., 2024a; 2024b preprint)" or similar.

For Vancouver/ICMJE biomedical citations, the NLM explicitly recommends updating preprint citations once the peer-reviewed version is available, unless the preprint and published version differ materially. For APA and MLA, the same guidance applies — the peer-reviewed version is authoritative.

• Treating a preprint as a journal article (adding volume/issue/pages) — preprints don't have these; leave the journal fields empty
• Missing the "[Preprint]" flag in Vancouver/Harvard — readers can't tell the source has not been peer-reviewed
• Using the PDF URL instead of the abstract URL — always cite the abstract page (e.g., arxiv.org/abs/XXXX.XXXXX), not the PDF download link
• Citing a withdrawn preprint — check the arXiv/bioRxiv page for withdrawal notices, or search Retraction Watch for preprint retractions, before citing
• Mixing up arXiv identifiers and DOIs — both are valid but the DOI (10.48550/arXiv.XXXX) is preferred for APA 7