How to find the DOI for any article

APA asks for the DOI of every work that has one, whether you read the online or the print version. Finding it takes a minute if you know where to look. Confirming it is the right one takes a minute more.

What a DOI is

A DOI (digital object identifier) is a permanent ID for a published work. It has a prefix and a suffix separated by a slash, as in 10.1000/182. Putting https://doi.org/ in front of it gives a link that takes a reader to the work, and the link keeps working if the publisher moves the page. The DOI Foundation describes the DOI as a persistent identifier: the address behind it can be updated without changing the DOI.

DOIs are registered through more than one agency. Crossref is the main registry for journal articles, books and conference papers. DataCite registers DOIs for datasets, theses and other research outputs. This is why a search of one registry can come back empty for a work that does have a DOI.

Where to look

Try these in order.

1. The article itself. The DOI is usually printed on the first page of the PDF, near the journal name or the copyright line, and listed on the article’s web page near the title or abstract.
2. A database record. Library databases show the DOI in the record for an article, and many can export a citation that includes it.
3. Crossref Metadata Search. At search.crossref.org you can search by title and author. Crossref registers DOIs for journal articles, books and conference papers.
4. Crossref Simple Text Query. Paste a complete reference, one per line with a blank line between references, and the tool tries to find one DOI for each. It accepts up to 1,000 references at a time. An option lists every possible match when the tool cannot decide on one.

Confirm it is the right DOI

A search result can be close and still wrong. Two papers can share a title, and a text query can return a false match. Before you copy a DOI into your reference list:

• Put https://doi.org/ in front of it and open the link.
• Check that the page shows the same title, authors and year as your source.
• If the page shows a different paper, the DOI is wrong. Go back to your search.

This matters most for references from an AI tool. A DOI in the correct format is easy to produce and says nothing about whether it exists. The post on why AI tools invent citations covers that problem.

How to write it

Write the DOI as a full link: https://doi.org/10.1000/182. Crossref’s display guidelines say to use https and to leave off labels such as “doi:” and the old “dx.doi.org” form. APA says the same: even if the article printed its DOI in an older form, standardize it to the https://doi.org/ form. Older links that use dx.doi.org still work, but new references should not use them.

Copy and paste the DOI instead of typing it, and do not change its capitalization or punctuation. Capital letters do not change which work a DOI points to, since the DOI Handbook treats DOI names that differ only in the case of basic Latin letters as equivalent, but APA still asks you to copy it as shown. Do not put a period after the DOI. APA says a final period can break the link.

A long DOI can be shortened. APA allows a shortDOI made with the service run by the International DOI Foundation. A work has only one DOI and one shortDOI. Open the shortened link and confirm it lands on the right article before you use it.

When there is no DOI

Not every source has one. Books are normally identified by an ISBN instead, and many web pages have neither. If Crossref has no record for an article, the article may have no DOI, or its DOI may be registered with another agency, such as DataCite.

• APA: a print work with no DOI gets neither a DOI nor a URL. An online work from a website gets its URL, as long as the link will work for readers. A work from most academic research databases gets no URL and no database name, because those works are widely available. If a work has both a DOI and a URL, give only the DOI. See APA’s page on DOIs and URLs.
• Books: look up the ISBN. The ISBN to citation tool builds the reference from it. APA does not print the ISBN in the reference itself.
• Never guess. A DOI that is almost right points to a different work. Leave it out, or find the correct one.

Checking a list

For one DOI, DOI to citation reads the published record and writes the citation in APA, MLA, Chicago, Harvard or IEEE. For a whole reference list, the reference checker looks up each DOI directly and tells you when a DOI belongs to a different paper than the one you wrote. It reports “Couldn’t verify” for a reference it cannot find, which is not the same as saying the source does not exist.