Digital Object Identifiers (DOIs)


A DOI, or digital object identifier, is an alpha-numeric string that is associated with a particular publication. It is similar to a URL (a uniform resource locator), the web link you see in your browser’s address bar. However, a DOI is more stable and will remain permanently attached to a publication.

DOIs are used in a number of publication styles. Here we focus on the proper way to use DOIs in APA style.

Current Guidelines

The American Psychological Association follows the guidelines for DOIs provided by Crossref, the organization that helps publishers create consistent citation linking. Crossref’s latest guidelines (ones adopted by the APA) suggest that a proper DOI should be in the following format (the letter being a variable number or letter):

Let’s take a closer look at the component parts of a DOI:

Note that every DOI will include the number 10 at the start of the prefix. The next number is at least four digits long and is associated with the registrant, a particular publisher or organization. The suffix consists of any number of letters and numbers.

When citing an online source with a DOI, add it at the end of your citation:

Wittles, Q. (2011). Freud and the art of doodling. Art and Psychology, 19, 22-33.

Make sure you don’t add a period afterwards, as that may mess up the link.

How to Find a DOI

Most often you will find the DOI at the beginning of the article (look on the first page, above the title or in the header and footer).

If you’re using an academic database, you will also often find the DOI listed in the information for the article:

Either way, you may still need to edit the link to get rid of “dx” and the library extension (in this case “”):



Note that normally we would use HTTPS instead of HTTP, but older formats are still valid (see below).

Older Methods

Increasingly, the goal is to make DOIs clickable, so that they function as an actual hyperlink.  This was not as much the case when the last edition of the APA style guide came out (in 2009). Back then DOIs were cited as follows:


In other words, the DOI was considered to start with the number 10.

In 2011, this approach was updated. Instead of starting with “doi:” the citation began with “”:

In 2017, Crossref again updated the guidelines (as described above). Gone is the “dx” and the transfer protocol (HTTP) should now be a secure one (HTTPS).

The good news is that older DOIs are still acceptable in APA style.  So all of the following formats are permissible, though the first is preferred:



If you’re doubtful about the usefulness of DOIs, just take a DOI (not one from this article–they’re mostly made up) and copy it in your browser’s address bar (then press Enter). Alternatively you can can go directly to the DOI resolver at Knowing the DOI allows you to easily find the text it belongs to.


For more information about DOIs, please consult pp. 188-92 of the Publication Manual of the American Psychological Association (6th ed.).

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