How to Use DOIs in APA, MLA, and Chicago Citations

How to Use a DOI in a Citation: Quick Answer

Copy the identifier that starts with 10., strip any campus ezproxy host, and write it as https://doi.org/10.… at the end of the reference. Do not add doi: or DOI: in front. Do not keep a publisher URL or a database session link beside a working DOI. Test the link at https://doi.org before you submit. Then apply your style's last-character rule: APA 7 leaves the DOI with no closing period; MLA 9 ends the Works Cited location with a period; Chicago 18 puts a period after the DOI in a note and after it in the bibliography.

What a DOI Is — and What This Page Leaves to Lookup

The DOI Foundation governs the identifier under ISO 26324 (approved 2010, published 2012, revised 2022). A DOI names an object persistently. It is not the URL in your address bar, and it is not a quality badge. You cannot mint one yourself; Crossref, DataCite, and other registration agencies assign names through their members. CMOS 10.55, in What's New in the 18th Edition, notes that DOI is a trademark while the spelled-out form “digital object identifier” may be lowercased.

That official example is the DOI Handbook itself. Prefix 10.1000 is the International DOI Foundation. Suffix 182 is this handbook edition. Prefacing the name with https://doi.org/ is what makes the string a link the proxy can resolve. This page assumes you already have a name that resolves to the work you read. If you do not, stop here and use How to Find a DOI — Crossref Metadata Search, Simple Text Query, DataCite Commons, and the ezproxy-stripping step live there so the two URLs do not clone each other.

Write Every DOI as https://doi.org/10.…

Crossref's display guidelines, effective March 2017, are the publisher-facing rule the three student handbooks now follow. On 1 September 2022 Crossref added that the 2017 rules were not changing (an accessibility recommendation for landing-page links was still being finalized). leftover-Crossref-doc-colon: the same page's FAQ still answers “Why not use doi: or DOI:?” with the sentence that doc:/DOI: is not a valid display form — the first token is a leftover for doi:. Crossref is explicit that doi: never became a native browser scheme, and that dx.doi.org is a leftover resolver hostname.

The same registered name can appear four ways on a PDF or a database record. Standardize it before you paste it into a paper. The APA Style sample below is Grady, Her, Moreno, Perez, and Yelinek (2019) in Psychology of Popular Media Culture — DOI 10.1037/ppm0000185 — the journal-article example still reprinted from the APA Style Center (Incapsula-blocked on 18 October 2026; confirmed from the 7th-edition Journal Article Reference Checklist). The 3 March 2026 Common Reference Examples Guide now leads with Niepel et al. (2025) instead. leftover-Niepel-DOI-wrap is that PDF's line break after https://doi.org/10.1037/.

A campus proxy is not part of the identifier. Rewrite https://doi-org.ezproxy.college.edu/10.1037/ppm0000185 to https://doi.org/10.1037/ppm0000185 so a reader off campus can resolve it. Do not invent a 10. string. If doi.org 404s or lands on a different title, you do not yet have this work's DOI.

APA 7: Include the DOI, Omit the Period

APA Style 7th edition (2020) treats the DOI as the last element of the reference (Publication Manual §§9.34–9.36; the public restatement is DOIs and URLs). The live Style Center page was Incapsula-blocked on 18 October 2026; the same “when to include” bullets are reprinted on DePaul's APA 7 guide. Include a DOI for every work that has one, including a print volume you never opened online. If the work has both a DOI and a URL, keep only the DOI. Do not write “Retrieved from” or “DOI:” in front of the link. Present the link as a live hyperlink (blue and underlined) or as plain black text — both are acceptable. For most journal articles taken from an academic research database and lacking a DOI, APA wants neither the database name nor a session URL: the reference matches the print form. The Reference Guide for Journal Articles, Books, and Edited Book Chapters (last updated 23 March 2026) repeats the period rule in one line: “Do not put a period after the DOI.”

Those strings are official samples, not reconstructed citations. Notice the missing period after each DOI. leftover-APA-2025-cite-handout: the 3 March 2026 Common Reference Examples PDF still tells you to cite the handout as American Psychological Association. (2025). leftover-APA-e0222224-source-only: the elements of reference list entries table, reprinted on Alamo Colleges (last updated 29 May 2026), shows only the source fragment PLoS ONE, 14(9), Article e0222224. https://doi.org/10.1371/journal.pone.0222224 — not a full reference. That DOI does resolve (Loda et al., 9 September 2019, a scoping review of peer-assisted learning). Copy Jerrentrup when you need a complete article-number model; do not invent authors for the e0222224 fragment. APA 9.36 also allows a shortened DOI, but only from the International DOI Foundation's ShortDOI service — not from bit.ly. Most student papers should keep the standard https://doi.org/10.… form so a grader can recognize it. Worked journal punctuation beyond the DOI lives in How to Cite a Journal Article in APA. Book DOIs sit where a URL would go; see How to Cite a Book in APA.

MLA 9: Prefer the DOI, Then End with a Period

MLA Handbook, 9th edition (2021), puts the DOI in the Location slot. Handbook 5.84 (p. 188) ranks locations. Handbook 5.93 requires the https://doi.org/ prefix even though ordinary URLs usually drop https:// (5.96). The Style Center (30 October 2024; opened 18 October 2026) reprints both sentences and a Project MUSE example. leftover-Bockelman-space is that post's HTML wrap: a space after the opening quotation mark (“ Buenos Aires) and a space after the en dash (pp. 37– 63). Quote the leftover, then use the recoverable string without those wraps. A second Style Center post, page range and DOI (11 August 2016; leftover-eighth-edition-banner), shows that an online-only paginated article may keep or drop the page range in front of the DOI.

Every official MLA DOI string above ends with a period after the DOI. That is the opposite of APA 7, and it is the mistake the old version of this page taught as a universal rule. Goldman is the Style Center's no-DOI contrast: JSTOR's stable URL, https:// dropped under 5.96, still ends with a period. Do not paste an ezproxy search URL. Full Works Cited slot order is in How to Cite a Journal Article in MLA.

Chicago 18: A DOI URL in Notes-Bibliography and Author-Date

The Chicago Manual of Style, 18th edition (2024), moved DOI display into chapter 13. CMOS 13.7 wants the URL form and treats doi:10… as deprecated. The University of Portland restatement (opened 18 October 2026) uses https://doi.org/10.1086/718629 as the display example — that DOI resolves to Lorraine Daston, “Dreams of the Universal Library.” CMOS 1.37 defines the identifier. CMOS 14.72 prefers the database name over a login URL when there is no DOI. CMOS 13.11, expanded in the 18th edition's What's New list, rejects third-party shorteners, including ShortDOI — the opposite of APA 9.36. The current Notes and Bibliography citation guide still says to include “a URL (preferably one based on a DOI; see CMOS 13.7).” Its worked journal examples, opened the same day, are Kwon (2022), Lindquist (2023), Dittmar and Schemske (2023), and Snyder et al. (2025) — not the older Keng, Lin, and Orazem (2017) classroom copy. leftover-CMOS-Founder-s is the electronic-book shortened note on that page: Founder s’ Constitution, with a space inside Founders’.

In a note the DOI follows the cited pages and a comma. In the bibliography the DOI follows the article's full page range and a period. Author-Date keeps the year after the author, drops no. before the issue, and still ends with the DOI URL. CMOS does not require a database name once a DOI is present. Notes versus Author-Date layout beyond the DOI is in How to Cite a Journal Article in Chicago.

An Article ID Is Not a DOI

Open-access journals often print an article identifier such as e0318239 or e0193972 beside the DOI. Students paste the shorter string into https://doi.org/ and get a 404. CMOS 14.71 lets that article ID replace the page range; the DOI URL is still required when one exists. The current Quick Guide's seven-author PLOS ONE sample is the Chicago worked case. APA 7 writes the word Article before an eLocator and then adds the DOI — two different slots — as in Jerrentrup et al. (2018) above.

e0318239 is the PLOS article ID. 10.1371/journal.pone.0318239 is the DOI. Only the second string belongs after https://doi.org/. The University of Portland CMOS 18 display example https://doi.org/10.1086/718629 is the same URL pattern without an article ID — still https://doi.org/ plus the 10. name, never doi:10.1086/718629.

leftover-OWL-doi-colon: Do Not Copy Purdue OWL's DOI Chart

The Purdue OWL “DOIs vs. URLs” page (opened 18 October 2026) is still useful for the high-level contrast — a DOI is static, a URL can move — and it uses a real article, Ryan LaMothe's “Pebbles in the Shoe: Acts of Compassion as Subversion in a Market Society” in Pastoral Psychology. leftover-OWL-doi-colon is the Quick Guide on that same page. It still tells APA, MLA, and Chicago writers to precede a DOI with a lowercase doi: label. For APA it still offers doi:0000000/000000000000 or “Retrieved from” before a URL. Those are APA 6 leftovers. APA 7, MLA 9 §5.93, and CMOS 13.7 all want https://doi.org/ and drop “Retrieved from.” leftover-OWL-purdue_owl-html is the page's own URL specimen https://owl.purdue.edu/owl/purdue_owl.html, which redirected to https://owl.purdue.edu/owl/ when opened.

When the Work Has No DOI

Absence of a printed DOI is not proof that none exists — many pre-2000 articles received one later. Search Crossref before you give up; the lookup steps are on How to Find a DOI. If nothing resolves to this work, each style has a different empty slot. The official no-DOI contrasts are Goldman's JSTOR permalink (MLA) and Hebert's EBSCOhost line (CMOS).

DOI versus URL, PMID, ISBN, arXiv, and Article ID

A DOI is one identifier family. Students mix it with four others that look similar on a database record. Only the DOI belongs in the https://doi.org/ slot.

Vaswani et al., “Attention Is All You Need” (2017), resolves at https://doi.org/10.48550/arXiv.1706.03762 and at https://arxiv.org/abs/1706.03762. Cite the DOI form in APA, MLA, or Chicago. Watson and Crick's 1953 Nature letter is https://doi.org/10.1038/171737a0 — a retrospective Crossref name, which is why “old article, therefore no DOI” is not a safe shortcut. Short definitions stay in the glossary: DOI, PMID, ISBN, arXiv id.

Line Breaks, Proxies, ShortDOI, and Multiple Names

• Copy, do not retype. A single wrong character 404s the resolver. Paste from the PDF, the publisher page, or Crossref. leftover-Niepel-DOI-wrap is what happens when a PDF already breaks the URL: join 10.1037/ to edu0000946 before you cite.
• Break a long DOI before a slash or a hyphen, never by inserting a hyphen that is not in the name. Do not “clean up” angle brackets or parentheses inside a suffix — 10.1175/1520-0442(1988)001<0715:COAPSR>2.0.CO;2 is a real DOI.
• Strip ezproxy hosts before you cite. The identifier is 10.…, not your campus login hostname.
• ShortDOI is a style fight. APA 9.36 allows the Foundation's shortdoi.org output. CMOS 13.11 tells you not to use ShortDOI, Bitly, or TinyURL. MLA 5.93 wants the ordinary https://doi.org/ form. Crossref itself says ShortDOIs “are not really actual DOIs” and prefers minting a short suffix in the first place.
• Two DOIs for one title usually means two objects — a preprint and the version of record, or a chapter and the book. Cite the version you read. Do not pick the prettier string.
• http://doi.org and https://doi.org both resolve. Write https://. DOI.org in a citation looks sloppy; the hostname is case-insensitive on the wire, but every current handbook prints lowercase doi.org.

DOIs on Books, Datasets, Conference Papers, and Preprints

The formatting rule does not change with the source type: if a DOI exists, write https://doi.org/10.… and apply your style's period rule. What changes is where the identifier is printed and which registration agency minted it. Crossref's own bibliography display sample is a Vancouver-style line ending in the same URL form the student handbooks want.

• Journal articles. Crossref. Still the most common student case. See the APA, MLA, and Chicago journal guides linked below.
• Books and chapters. Some university-press and STEM books carry a DOI on the copyright page or the publisher HTML. APA 7 §10.2 and CMOS 14.58–62 put that DOI where a URL would go. Levenson et al. (2025) above is the current APA book sample.
• Conference papers. IEEE Xplore, ACM Digital Library, and many proceedings now deposit Crossref DOIs. Cite the paper's DOI, not the conference website.
• Datasets and software. DataCite names, often from Zenodo, Figshare, Dryad, or ICPSR. APA has a dedicated path in How to Cite a Dataset in APA. Software deposits may have a version DOI and a concept DOI; copy the version you actually used.
• Preprints. bioRxiv and medRxiv use Crossref; arXiv now assigns DataCite DOIs. A later journal article is a different object with a different DOI — cite the version you read, and say it is a preprint if your style has a slot for that.

Mistakes This Page Used to Teach — and Leftovers Opened 18 October 2026

An older version invented a 2023 Journal of Adolescent Psychology article by Smith and Jones with the fake DOI 10.1037/example.2023.001, cited Chicago 17 instead of CMOS 18, and told every reader to omit the period after a DOI. Those fabricated citations and that style-agnostic period rule are gone. The August 2026 refresh used Keng, Lin, and Orazem (2017) from an earlier CMOS Quick Guide; that article is real (https://doi.org/10.1086/690235) but is no longer the current official journal sample. Use Niepel or Grady (APA), Berman and Bockelman (MLA), and Kwon, Lindquist, or Snyder (Chicago) instead. leftover-OWL-doi-colon is the live OWL chart that would put the old doi: prefix back if you copied it.

Paste the DOI Instead of Retyping the Reference

Zotero, Mendeley, and EndNote all store a DOI field and can write https://doi.org/ when the style file is current. Still check the last character: an APA 6 style file will emit doi:10. into an APA 7 paper — the same leftover-OWL-doi-colon form. If you already have the identifier, the generator can pull Crossref or DataCite metadata so you are not transcribing authors from a PDF header. Then compare the ending against Niepel, Bockelman, or Kwon.

Related guides and tools

• How to Find a DOI
• How to Cite a Journal Article in APA
• How to Cite a Journal Article in MLA
• How to Cite a Journal Article in Chicago
• How to Cite a Book in APA
• How to Write a Bibliography
• How to Cite a Dataset in APA
• DOI to APA converter
• DOI to MLA converter
• DOI to BibTeX converter
• DOI in the glossary