Do I need both a URL and a DOI in the citation?

No. APA 7, MLA 9, and CMOS 18 all prefer the DOI and drop the publisher or database URL once a DOI exists. APA says this in so many words: if a work has both, include only the DOI.

Should there be a period after the DOI?

It depends on the style, which is why a single house rule fails. APA 7: no period after the DOI or URL. MLA 9: yes — the Location element ends with a period, and every official Style Center DOI example includes it. Chicago 18: the current Kwon note and bibliography close with a period after the DOI URL.

How do I format a DOI in APA 7?

Write https://doi.org/ plus the 10. name as the last element, with no period after it, no “Retrieved from,” and no second URL. Include that DOI even if you read the print issue. Niepel et al. (2025) is the current Common Reference Examples sample: …772–788. https://doi.org/10.1037/edu0000946

How do I format a DOI in MLA 9?

Handbook 5.93: always precede the DOI with https://doi.org/. Handbook 5.84: choose DOI, then permalink, then URL. Put a period after the DOI. Bockelman's Project Muse line is the Style Center's worked case.

Is dx.doi.org still acceptable?

It still resolves. Crossref dropped dx from the recommended display in March 2017, restated that the 2017 rules were not changing on 1 September 2022, and wants https://doi.org/. APA, MLA, and CMOS 18 follow that form. Rewrite older dx.doi.org or doi: printings when you build the reference list.

What if the article has no DOI?

Search Crossref first; many older articles received a DOI later. If nothing matches, APA usually cites a widely available journal with no URL; MLA gives a permalink or URL (Goldman on JSTOR is the Style Center contrast); Chicago often names the database (14.72) instead of a login link (Hebert on EBSCOhost).

Can I use a ShortDOI or a bit.ly link?

APA 9.36 allows a ShortDOI only from shortdoi.org. CMOS 13.11 rejects third-party shorteners, and Massey and other CMOS 18 restatements name ShortDOI, TinyURL, and Bitly together. MLA wants the ordinary https://doi.org/ form. When in doubt, keep the full URL.

Is an article ID the same thing as a DOI?

No. Snyder et al. (2025) prints both: e0318239 is the PLOS article ID that can stand in for pages under CMOS 14.71; https://doi.org/10.1371/journal.pone.0318239 is the DOI. APA writes Article plus the eLocator, then the DOI. Pasting the short ID after doi.org/ 404s.

Does a DOI prove the source is scholarly?

No. A DOI is an identifier, not a peer-review stamp. Datasets, preprints, reports, and some magazine items have DOIs. Evaluate the work the way you would any other source; the DOI only tells a reader how to find the same object later.

Should the DOI be a blue hyperlink in my paper?

APA 7 accepts the word processor's default blue underline or plain black text, and wants the link live if the file will be read on screen. MLA and Chicago also treat the DOI as a URL; follow your instructor on color. Never hide the DOI behind the word “link.”

Can I cite DOI.org with capital letters?

The resolver does not care, but every current handbook and the Crossref display guidelines print https://doi.org/ in lowercase. Write that.

How to Use a DOI in Citations (APA 7, MLA 9, CMOS 18) [2026]

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.

Official endings from the current style-center samples

APA 7 (Common Reference Examples Guide, 3 March 2026) — no period after the DOI

Niepel, C., Hausen, J. E., Weber, A. M., & Möller, J. (2025). Understanding mean-level and intraindividual variability in state academic self-concept: The role of students’ trait expectancies and values. Journal of Educational Psychology, 117(5), 772–788. https://doi.org/10.1037/edu0000946

MLA 9 (Handbook 5.93 / Style Center database post) — period after the DOI

Bockelman, Brian. “Buenos Aires Bohème: Argentina and the Transatlantic Bohemian Renaissance, 1890–1910.” Modernism/Modernity, vol. 23, no. 1, Jan. 2016, pp. 37–63. Project Muse, https://doi.org/10.1353/mod.2016.0011.

Chicago 18 Notes-Bibliography (current Quick Guide) — period after the DOI

Kwon, Hyeyoung. “Inclusion Work: Children of Immigrants Claiming Membership in Everyday Life.” American Journal of Sociology 127, no. 6 (2022): 1818–59. https://doi.org/10.1086/720277.

Crossref canonical display (March 2017; still current)

https://doi.org/10.xxxx/xxxxx

The decision this page exists to teach. Lookup belongs on the sibling find-a-DOI guide.
Question	APA 7 (§§9.34–9.36)	MLA 9 (§§5.84, 5.93)	CMOS 18 (§§13.7, 13.11, 14.72)
DOI present	Include it even if you read print. Omit any URL.	Prefer DOI over permalink over URL.	Prefer a DOI URL; or name the database.
Closing punctuation	No period after the DOI or URL.	Period after the DOI (location ends the entry).	Period after the DOI in notes and in the bibliography.
Database, no DOI	Omit database name and URL for most journals.	Give permalink or URL, even if gated (5.84).	Name the database rather than a login URL (14.72).
ShortDOI / bit.ly	ShortDOI from shortdoi.org is allowed (9.36).	Write https://doi.org/ plus the full 10. name.	Do not use third-party shorteners, including ShortDOI (13.11).
Article ID next to a DOI	Write Article plus the eLocator, then the DOI.	Keep volume, issue, and DOI; add pages only if useful.	CMOS 14.71: the article ID can replace the page range; the DOI is still a separate URL.

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.

DOI Foundation

A DOI is a digital identifier of an object, any object — physical, digital, or abstract.

A DOI is a unique number made up of a prefix and a suffix separated by a forward slash. This is an example of one: 10.1000/182.

The DOI is not only persistent but it is "actionable" which means that you use it and something useful will happen.

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). Cite the guidelines themselves as “Crossref Display Guidelines (March 2017)”, https://doi.org/10.13003/5jchdy. Crossref is explicit that doi: never became a native browser scheme, so it is not a valid display form, and that dx.doi.org is a leftover resolver hostname.

Crossref Display Guidelines (March 2017; restated 1 September 2022)

always be displayed as a full URL link in the form https://doi.org/10.xxxx/xxxxx

not be preceded by doi: or DOI:

not use dx in the domain name part of DOI links

and we recommend HTTPS (rather than HTTP).

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. The 3 March 2026 Common Reference Examples Guide now leads with Niepel et al. (2025) instead.

Four printings of one real DOI. Only the https://doi.org/ row belongs in a current student paper.
How it is labeled	What you copy	Do you cite this form?
https://doi.org/ URL	https://doi.org/10.1037/ppm0000185	Yes — APA 7, MLA 9, CMOS 18
Bare DOI name	10.1037/ppm0000185	Enough for lookup; prefix it before you cite
doi: prefix (older PDF)	doi:10.1037/ppm0000185	No — rewrite to https://doi.org/
Legacy proxy	http://dx.doi.org/10.1037/ppm0000185	Still resolves; do not prefer it

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). 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.

APA Style (7th ed.) — Publication Manual §§9.34–9.36, restated on the DOIs and URLs page

Include a DOI for all works that have a DOI, regardless of whether you used the online version or the print version.

Do not include both a DOI and a URL in a reference entry. If a work has both a DOI and a URL, include only the DOI.

Do not add a period after the DOI or URL.

For works without DOIs from most academic research databases, do not include a URL or database information in the reference because these works are widely available.

The preferred format of the DOI has changed over time; although older works use previous formats (e.g., "http://dx.doi.org/" or "doi:" or "DOI:" before the DOI number), in your reference list, standardize DOIs into the current preferred format for all entries

Official APA Style journal and book samples — keep these strings in English

Style Center journal-article sample (Grady et al., 2019)

Grady, J. S., Her, M., Moreno, G., Perez, C., & Yelinek, J. (2019). Emotions in storybooks: A comparison of storybooks that represent ethnic and racial groups in the United States. Psychology of Popular Media Culture, 8(3), 207–217. https://doi.org/10.1037/ppm0000185

Common Reference Examples Guide, 3 March 2026 (Niepel et al., 2025)

Niepel, C., Hausen, J. E., Weber, A. M., & Möller, J. (2025). Understanding mean-level and intraindividual variability in state academic self-concept: The role of students’ trait expectancies and values. Journal of Educational Psychology, 117(5), 772–788. https://doi.org/10.1037/edu0000946

Common Reference Examples Guide book with a DOI (Levenson et al., 2025)

Levenson, H., Jinich, S., Vaz, A., & Rousmaniere, T. (2025). Deliberate practice in emotionally focused couple therapy. American Psychological Association. https://doi.org/10.1037/0000436-000

Those strings are official samples, not reconstructed citations. Notice the missing period after each DOI. 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 — sentence case, italic volume, ampersand — 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) reprints both sentences and a Project MUSE example. A second Style Center post, page range and DOI (11 August 2016), shows that an online-only paginated article may keep or drop the page range in front of the DOI.

MLA Handbook, 9th ed.

For online works, the location, in order of preference, is the DOI, permalink, or URL

DOIs should always be preceded by https://doi.org/

MLA Style Center official examples — keep these strings in English

Bockelman (Handbook 5.93 / Style Center database post)

Bockelman, Brian. “Buenos Aires Bohème: Argentina and the Transatlantic Bohemian Renaissance, 1890–1910.” Modernism/Modernity, vol. 23, no. 1, Jan. 2016, pp. 37–63. Project Muse, https://doi.org/10.1353/mod.2016.0011.

Berman without pages

Berman, Russell. “The Necessity of Language Learning.” ADFL Bulletin, vol. 43, no. 2, 2015, https://doi.org/10.1632/adfl.43.2.11.

Berman with pages (also acceptable)

Berman, Russell. “The Necessity of Language Learning.” ADFL Bulletin, vol. 43, no. 2, 2015, pp. 11-14, https://doi.org/10.1632/adfl.43.2.11.

Goldman — no DOI, so a JSTOR permalink (Style Center contrast)

Goldman, Anne. “Questions of Transport: Reading Primo Levi Reading Dante.” The Georgia Review, vol. 64, no. 1, 2010, pp. 69-88. JSTOR, www.jstor.org/stable/41403188.

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 uses https://doi.org/10.1086/718629 as the display example. 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 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 are now Kwon (2022), Lindquist (2023), Dittmar and Schemske (2023), and Snyder et al. (2025) — not the older Keng, Lin, and Orazem (2017) classroom copy.

Chicago Manual of Style, 18th ed., citation guide and §13.7

For articles consulted online, include a URL (preferably one based on a DOI; see CMOS 13.7)

Official CMOS citation-guide journal example (Kwon, 2022)

Note (specific pages)

Hyeyoung Kwon, “Inclusion Work: Children of Immigrants Claiming Membership in Everyday Life,” American Journal of Sociology 127, no. 6 (2022): 1842–43, https://doi.org/10.1086/720277.

Bibliography (full page range)

Kwon, Hyeyoung. “Inclusion Work: Children of Immigrants Claiming Membership in Everyday Life.” American Journal of Sociology 127, no. 6 (2022): 1818–59. https://doi.org/10.1086/720277.

Author-Date reference list

Kwon, Hyeyoung. 2022. “Inclusion Work: Children of Immigrants Claiming Membership in Everyday Life.” American Journal of Sociology 127 (6): 1818–59. https://doi.org/10.1086/720277.

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 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 worked case. APA 7 writes the word Article before an eLocator and then adds the DOI — two different slots.

Official CMOS citation-guide article-ID sample (Snyder et al., 2025)

Note (specific pages plus article ID plus DOI)

Carl D. Snyder et al., “Extant Life Detection Using Label-Free Video Microscopy in Analog Aquatic Environments,” PLOS ONE 20, no. 3 (2025): 9–10, e0318239, https://doi.org/10.1371/journal.pone.0318239.

Bibliography (article ID in place of a page range)

Snyder, Carl D., Manuel Bedrossian, Casey Barr, et al. “Extant Life Detection Using Label-Free Video Microscopy in Analog Aquatic Environments.” PLOS ONE 20, no. 3 (2025): e0318239. https://doi.org/10.1371/journal.pone.0318239.

Author-Date reference list

Snyder, Carl D., Manuel Bedrossian, Casey Barr, et al. 2025. “Extant Life Detection Using Label-Free Video Microscopy in Analog Aquatic Environments.” PLOS ONE 20 (3): e0318239. https://doi.org/10.1371/journal.pone.0318239.

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.

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).

APA 7, no DOI

Print or most academic databases: stop after the page range. No URL, no database name.
Open website (not a database): add a working URL, still with no period after it.
Proprietary database (UpToDate, some ERIC items): name the database and give a resolvable URL or the database home page.

MLA 9 and CMOS 18, no DOI

MLA 5.84: permalink, then URL, even if the link is gated.
MLA usually drops https:// on ordinary URLs (5.96) — never on DOIs.
CMOS 14.72: prefer the database name over a session URL.
CMOS may use a stable publisher URL when the article is not in a library database.

Official no-DOI contrasts — keep these strings in English

MLA Style Center (Goldman in JSTOR)

Goldman, Anne. “Questions of Transport: Reading Primo Levi Reading Dante.” The Georgia Review, vol. 64, no. 1, 2010, pp. 69-88. JSTOR, www.jstor.org/stable/41403188.

CMOS Quick Guide note (Hebert in EBSCOhost)

B. T. Hebert, “The Island of Bolsö: A Study of Norwegian Life,” Sociological Review 17, no. 4 (1925): 310, EBSCOhost.

CMOS Quick Guide bibliography (Hebert)

Hebert, B. T. “The Island of Bolsö: A Study of Norwegian Life.” Sociological Review 17, no. 4 (1925): 307–13. EBSCOhost.

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.

If it does not start with 10. and resolve at doi.org to this work, it is not this work's DOI.
Identifier	What it names	What you put in the citation
DOI	The registered object (article, chapter, dataset, preprint)	https://doi.org/10.… in APA, MLA, and Chicago
Article ID / eLocator	The journal's own paper number (e0318239, Article e0225964)	Keep it in the pages slot. Do not paste it after doi.org/
Publisher or database URL	Today's webpage or a proxied PDF session	Use only when there is no DOI; never beside a DOI
PMID	A PubMed record, not the article's persistent ID	Do not write pubmed.ncbi.nlm.nih.gov instead of a DOI you already have
ISBN / ISSN	A book edition or the journal as a serial	Books may carry both an ISBN and a DOI; prefer the DOI when the style wants a link
arXiv id	A preprint version on arXiv	Current styles prefer the DataCite DOI 10.48550/arXiv. plus the id when one exists

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.
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.

Crossref Display Guidelines — official reference-list option 1

Soleimani N, Mohabati Mobarez A, Farhangi B. Cloning, expression and purification flagellar sheath adhesion of Helicobacter pylori in Escherichia coli host as a vaccination target. Clin Exp Vaccine Res. 2016 Jan;5(1):19-25. https://doi.org/10.7774/cevr.2016.5.1.19

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

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 or Snyder (Chicago) instead.

Failure modes graders actually mark.
What students do	Why it fails	Fix
Write doi:10.1037/ppm0000185	Crossref 2017; APA, MLA 5.93, CMOS 13.7	https://doi.org/10.1037/ppm0000185
Put a period after the DOI in APA	APA §§9.34–9.36: the period can break the link	Stop after the last character of the DOI
Omit the period after the DOI in MLA	MLA location is a core element that ends with a period	…https://doi.org/10.1632/adfl.43.2.11.
Paste e0318239 after doi.org/	That is the PLOS article ID, not the DOI	https://doi.org/10.1371/journal.pone.0318239
Cite the database URL next to a DOI	APA: DOI only. CMOS: DOI or database, not both	Keep the DOI; drop the proxy URL
Leave ezproxy in the host	Off-campus readers cannot resolve it	Rewrite the host to doi.org
Use bit.ly because the DOI is long	CMOS 13.11; graders cannot see the identifier	Keep https://doi.org/10.… or, in APA only, ShortDOI

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. 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.

Format the DOI in the style you were assigned

Paste a DOI into the generator, or convert a list. The human job that remains is the period, the database name, the article ID versus DOI, and confirming doi.org lands on the work you read.

Generate a citation from a DOI DOI to APA DOI to MLA How to find a DOI first

Frequently Asked Questions

Do I need both a URL and a DOI in the citation?: No. APA 7, MLA 9, and CMOS 18 all prefer the DOI and drop the publisher or database URL once a DOI exists. APA says this in so many words: if a work has both, include only the DOI.
Should there be a period after the DOI?: It depends on the style, which is why a single house rule fails. APA 7: no period after the DOI or URL. MLA 9: yes — the Location element ends with a period, and every official Style Center DOI example includes it. Chicago 18: the current Kwon note and bibliography close with a period after the DOI URL.
How do I format a DOI in APA 7?: Write https://doi.org/ plus the 10. name as the last element, with no period after it, no “Retrieved from,” and no second URL. Include that DOI even if you read the print issue. Niepel et al. (2025) is the current Common Reference Examples sample: …772–788. https://doi.org/10.1037/edu0000946
How do I format a DOI in MLA 9?: Handbook 5.93: always precede the DOI with https://doi.org/. Handbook 5.84: choose DOI, then permalink, then URL. Put a period after the DOI. Bockelman's Project Muse line is the Style Center's worked case.
Is dx.doi.org still acceptable?: It still resolves. Crossref dropped dx from the recommended display in March 2017, restated that the 2017 rules were not changing on 1 September 2022, and wants https://doi.org/. APA, MLA, and CMOS 18 follow that form. Rewrite older dx.doi.org or doi: printings when you build the reference list.
What if the article has no DOI?: Search Crossref first; many older articles received a DOI later. If nothing matches, APA usually cites a widely available journal with no URL; MLA gives a permalink or URL (Goldman on JSTOR is the Style Center contrast); Chicago often names the database (14.72) instead of a login link (Hebert on EBSCOhost).
Can I use a ShortDOI or a bit.ly link?: APA 9.36 allows a ShortDOI only from shortdoi.org. CMOS 13.11 rejects third-party shorteners, and Massey and other CMOS 18 restatements name ShortDOI, TinyURL, and Bitly together. MLA wants the ordinary https://doi.org/ form. When in doubt, keep the full URL.
Is an article ID the same thing as a DOI?: No. Snyder et al. (2025) prints both: e0318239 is the PLOS article ID that can stand in for pages under CMOS 14.71; https://doi.org/10.1371/journal.pone.0318239 is the DOI. APA writes Article plus the eLocator, then the DOI. Pasting the short ID after doi.org/ 404s.
Does a DOI prove the source is scholarly?: No. A DOI is an identifier, not a peer-review stamp. Datasets, preprints, reports, and some magazine items have DOIs. Evaluate the work the way you would any other source; the DOI only tells a reader how to find the same object later.
Should the DOI be a blue hyperlink in my paper?: APA 7 accepts the word processor's default blue underline or plain black text, and wants the link live if the file will be read on screen. MLA and Chicago also treat the DOI as a URL; follow your instructor on color. Never hide the DOI behind the word “link.”
Can I cite DOI.org with capital letters?: The resolver does not care, but every current handbook and the Crossref display guidelines print https://doi.org/ in lowercase. Write that.