Nov 14, 2022

What is a DOI? | APA, MLA, Chicago Formats

magnifying glass sitting on top of colorful file folders
A DOI makes it significantly easier for researchers to locate and cite published sources.

What is a DOI and what does it do?

You have probably seen reference lists with citations that end in a long number preceded by the abbreviation “doi,” or been told that your list is missing those. But what does “DOI” stand for? A DOI, meaning digital object identifier, is a unique alphanumeric string that is assigned (standardized by the International DOI foundation) to electronic journal articles, government reports, books, and other digital items that need to be identified in databases and on websites. Unlike URLs, DOIs never change, and many journals and citation styles now generally recommend including them in reference lists.

All DOIs start with the number 10 followed by a period, but they can be formatted in different ways. The correct format for your manuscript depends on the DOI citation style the target journal wants you to apply (and/or other author instructions):

doi:10.4324/9780203449530

https://dx.doi.org/10.4324/9780203449530

https://doi.org/10.1016/0014-4886(85)90123-2

Where is the DOI located?

If a journal publishes DOIs, then you will usually find them somewhere on the first page of an article, probably in the header or footer. 

how to locate the DOI at the top of an article

If you cannot find the DOI on the article itself, try clicking on “cite this article”, or search the journal website—it might be listed somewhere there instead.

How to find the DOI (DOI lookup)

There is no central DOI system that lists them all, but web search engines will usually show DOI names if you search for an article/book by title, name, or topic. If an article has a DOI, the number should be listed in the information about the article, which can be called “Detailed Record”, “Abstract”, or “Abstract/Details”. If you don’t see such an information record, click on the article title page. 

If all else fails, you can look for a DOI using the Crossref website. Crossref is an organization that assigns DOIs for research articles. If you do not find a DOI for an article on Crossref, you can safely assume that the article you are looking for does not have one. Sometimes university libraries provide their own doi-lookup service or a how-to page with instructions.

APA Style Guidelines for DOIs

Because the majority of publications are available and accessed online these days, reference list entries usually end with a DOI or, if an article doesn’t have one, a URL (uniform resource locator).

An APA citation for a journal article (consisting of author names, publication year, title, journal name, volume (and issue) number, and complete page range) should, whenever available, include a DOI. If you cannot find a DOI and the article was accessed through a website other than a database (e.g. the journal website), provide the URL instead—if there is no “share” button or the like, just copy the address bar of your browser directly into your reference list. If an article has no DOI and you found it on an academic database or read it in print format, then just omit the DOI number. And if an online article you want to cite has both a DOI and a URL, include the DOI only. No other alphanumeric identifiers (such as the International Standard Book Number (ISBN) or the International Standard Serial Number (ISSN)) should be included in APA Style references.

Pro-tip 1: Since some databases and archives require a login or subscription, provide the URL of the database or archive home page or login page instead of the URL for such works. The APA website explains such details here and offers advice for when an article has no DOI and the URL is no longer working or no longer provides readers access here.

Pro-tip 2: Manually check the DOIs in your reference list to make sure they all lead to the correct article before submitting your manuscript!

The APA also recommends that you: 

  • copy-paste DOIs directly from your browser into your reference list to avoid errors 
  • do not change capitalization or punctuation
  • do not add line breaks unless your word-processing program automatically does that
  • do not add a period after the DOI or URL because this may affect the link

DOI formatting for APA Style

In APA Style reference lists, both DOIs and URLs should be provided as hyperlinks, beginning with “http:” or “https:”. You don’t need to add “retrieved from” or “accessed through”, because hyperlinks directly lead to the article. You can add these links to your list by either using the default Word settings (usually blue font, underlined) or writing them in plain text. 

DOI example in APA Style

The recommended format for DOIs in reference lists is https://doi.org/xxxxx, with the “xxxxx” refering to the specific DOI number of the linked article.

While formats have changed over time (e.g., “http:/dx.doi.org/” or simply “DOI:” before the number used to be common ways of presenting them in older publications), the APA now recommends standardizing DOIs into the current preferred format. 

For example, even if an earlier published article has the DOI http:/dx.doi.org/10.1037/a0040251, change it to https://doi.org/10.1037/a0040251 to make sure it is up to date and in line with the current standards.

A full APA citation with a DOI looks like this:

Gatz, M., Smyer, M. A., & DiGilio, D. A. (2016). Psychology’s contribution to the well-being of older americans. American Psychologist, 71(4), 257–267. https://doi.org/10.1037/a0040251

MLA Style Guidelines for DOIs

The MLA Style Guidelines also state to include DOIs in reference lists, but recommend the simple format “doi:” (e.g. doi:10.1037/a0040251). If an article has no DOI, then include a stable URL, such as www.jstor.org/stable/43832354)

DOI example in MLA Style

Gatz, Margaret, Michael A. Smyer, and Deborah A. DiGilio. “Psychology’s contribution to the well-being of older americans.” American Psychologist 71.4 (2016): 257. doi:10.1037/a0040251

Chicago Style Guidelines for DOIs

The Chicago Manual of Style, like most other style guides, also suggests that references to online sources should include a DOI if possible, a URL if not, or some other piece of information (e.g., a database title) that allows the reader to locate the online source of an article. The preferred format for Chicago Style publications is https://doi.org/10.1086/690235.

DOI example in Chicago Style

Keng, Shao-Hsun, Chun-Hung Lin, and Peter F. Orazem. “Expanding college access in Taiwan, 1978–2014: effects on graduate quality and income inequality.” Journal of Human Capital 11, no. 1 (2017): 1-34. https://doi.org/10.1086/690235

Frequently Asked Questions about DOI

How do I find the DOI of a journal article?

You can usually see the DOI (starting with “doi.org” or “DOI:”) somewhere on the first page of an article when you open it on any academic database. If you don’t see such a number, then look for a link that says “cite article” or “details”.

If you cannot find an article’s DOI anywhere, your university library or websites like Crossref can locate it when you search by author, title, journal, and/or year of publication.

Should I use a URL or DOI in a citation?

As a rule of thumb, use a DOI whenever it is available and a URL if even Crossref.org does not find a DOI for the article you want to cite.

How do I format a DOI in APA Style?

Add the DOI to the end of the citation, preceded by “https://doi.org/”:

Gatz, M., Smyer, M. A., & DiGilio, D. A. (2016). Psychology’s contribution to the well-being of older americans. American Psychologist, 71(4), 257–267. https://doi.org/10.1037/a0040251

How do I format a DOI in MLA Style?

In MLA style citations, the DOI also follows the full citation, but a simple “doi” is preferred:

Gatz, Margaret, Michael A. Smyer, and Deborah A. DiGilio. “Psychology’s contribution to the well-being of older americans.” American Psychologist 71.4 (2016): 257. doi:10.1037/a0040251

How do I format a DOI in Chicago Style?

Chicago Style reference list entries follow a different style overall but, like APA citations, end in a DOI preceded by “https://doi.org/”: 

Keng, Shao-Hsun, Chun-Hung Lin, and Peter F. Orazem. “Expanding college access in Taiwan, 1978–2014: effects on graduate quality and income inequality.” Journal of Human Capital 11, no. 1 (2017): 1-34. https://doi.org/10.1086/690235

Make sure your manuscript/paper is submission ready! 

As always, our Wordvice Editors are there to help you improve the flow and expression of your academic text and ensure it conforms to the required style. Get paper editing or manuscript editing for your work and submit your research documents to journals with confidence.

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