What a DOI Is, and How to Cite a Paper That Has None

The student pulls up a PDF from their university course reader, follows APA's sample list in formatting the reference, and freezes when they get to the DOI line. No superscript number, no printed link, nothing at the bottom of the first page where a DOI typically goes. The citation generator moves on, leaving the field blank if it is a program that can do such things.

How to cite a paper that has no DOI depends on two things: which style guide is in use, and, in APA's case, what kind of source the paper actually is. MLA does not ask that second question at all. Both rules are short. Neither is obvious until you have seen it once.

Getting the source type right is a small piece of a much larger picture. TextPulse's guide to referencing styles covers how APA, MLA, Chicago and half a dozen other systems differ at the structural level; this piece stays on one narrow failure point inside that picture: what happens when the identifier every style guide assumes exists simply is not there.

What a DOI Actually Is

A DOI, short for Digital Object Identifier, is a persistent identifier, not a dressed-up web address. The DOI Foundation describes it as a digital identifier that can point at an object of any kind, physical, digital or abstract, administered under the international standard ISO 26324. Individual DOIs are issued through registration agencies rather than by the Foundation itself; Crossref is the best known of these for scholarly journal articles.

Structurally, a DOI is a prefix and a suffix separated by a slash, something like 10.1000/182. The prefix identifies the publisher or registrant, the suffix identifies the specific item, and once assigned, that string does not change even if the publisher moves the article to a new server.

That stability is exactly why APA and MLA both reach for a DOI ahead of a URL whenever one exists. A URL can rot the day a journal migrates its website. A DOI, maintained correctly by its registration agency, keeps resolving to the work's current location regardless of what happens to the page behind it.

When a DOI does exist, APA's current guidance is exact about its shape: a single resolvable link that starts with https, then doi.org, then the prefix and suffix, with nothing else in front of it. There is no "doi:" label. There is no period at the end either: APA's own guidance says a trailing period "may interfere with link functionality," so the period is left off on purpose.

How to Tell Whether a Source Genuinely Has No DOI

Not every source without a visible DOI is actually without one. Publishers sometimes leave the identifier off the PDF itself while still registering one for the article, which then shows up on the publisher's own landing page or in a database record even though it never made it onto the file a student downloaded.

• Search the exact title on the publisher's own site instead of a repository copy. The DOI usually sits next to the abstract even when it never made it onto the PDF itself.
• Check the database record directly, not just the downloaded file. Many academic databases display a DOI field even when the article's own PDF does not print one.
• Try a DOI look-up tool, such as Crossref's own search, which matches a title and author list to a registered DOI directly.

A source that still turns up nothing after all three checks is genuinely without a DOI, and that is exactly where APA and MLA stop agreeing with each other.

How to Cite a Paper That Has No DOI in APA

APA's rule is not one fixed rule. It branches by source type, and the reference list entry changes shape depending on which branch applies.

A print work with no DOI takes nothing extra: no DOI, no URL, no database name, just the standard author, date, title and publication details.

A source pulled from the open web, with no DOI printed anywhere, takes a working URL in the DOI's place instead.

A source read through an academic database usually takes neither. APA's own guidance treats database-hosted scholarly work as widely available elsewhere, so the reference list leaves the location off entirely rather than pointing at a subscription a reader may not have.

The exception is a source found only in a proprietary or limited-circulation database. That entry takes the database name plus a URL, because that source genuinely is not available anywhere else the way an ordinary academic-database source usually is.

How to Cite a Paper That Has No DOI in MLA

MLA does not ask what kind of source it is looking at. It applies exactly one preference order, every time: a DOI first, a permalink second, and a plain URL third, used only when neither of the first two exists.

MLA's own guidance is explicit that the order holds regardless of access. A permalink or URL is usable, in the organization's own words, "even if the permalink or URL leads to gated content," because the rule is about which identifier to print, not about whether every reader can click straight through.

That single order is what makes MLA simpler to apply than APA in this one respect. There is no branching decision about source type first: find the best available identifier in that order, use it, and move on.

APA vs MLA: The Same Missing DOI, Two Different Rules

Lined up side by side, the difference in approach is easier to see than to describe: one style keeps asking what kind of source this is, the other never asks the question at all.

Source type	APA (7th edition)	MLA (9th edition)
Print work, no DOI	No DOI or URL at all	DOI, then permalink, then URL, in that order every time
General website, no DOI	Include a working URL	DOI, then permalink, then URL, in that order every time
Academic database, no DOI	Usually no URL either, since the work counts as widely available	DOI, then permalink, then URL, in that order every time
Proprietary or limited-circulation database	Include the database name plus a URL	DOI, then permalink, then URL, in that order every time

For a source that does have a DOI, converting it straight into a formatted reference is what a DOI-to-citation tool is for: paste the identifier in, and the citation comes back formatted, without retyping the author list and title by hand.

In LaTeX the same problem is a field rather than a formatting decision, and BibTeX against BibLaTeX is compared separately. Reformatting a reference list for a different journal is its own page.

For the no-DOI cases above, the same logic still applies once the source type is settled: author, date, title, publication details, then whichever DOI-or-URL rule fits. A citation generator that supports both APA and MLA formats the remainder correctly once those two decisions are made, which is usually where a writer trips under deadline pressure, not the DOI rule itself.