This page addresses when to include digital object identifiers (DOIs) and uniform resource locators (URLs) in APA Style references. Also check out the related topic of when to include database information in references.
The DOI or URL is the final component of a reference list entry. Because so much scholarship is available and/or retrieved online, most reference list entries end with either a DOI or a URL.
- A DOI is a unique alphanumeric string that identifies content and provides a persistent link to its location on the internet. DOIs can be found in database records and the reference lists of published works.
- A URL specifies the location of digital information on the internet and can be found in the address bar of your internet browser. URLs in references should link directly to the cited work when possible.
When to include DOIs and URLs
Follow these guidelines for including DOIs and URLs in references:
- Include a DOI for all works that have a DOI, regardless of whether you used the online version or the print version.
- If a print work does not have a DOI, do not include any DOI or URL in the reference.
- If an online work has both a DOI and a URL, include only the DOI.
- If an online work has a URL but no DOI, include the URL in the reference as follows:
- For works without DOIs from websites (not including academic research databases), provide a URL in the reference (as long as the URL will work for readers).
- 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 reference should be the same as the reference for a print version of the work.
- For works from databases that publish original, proprietary material available only in that database (such as the UpToDate database) or for works of limited circulation in databases (such as monographs in the ERIC database), include the name of the database or archive and the URL of the work. If the URL requires a login or is session-specific (meaning it will not resolve for readers), provide the URL of the database or archive home page or login page instead of the URL for the work. See the page on including database information in references for more information.
- If the URL is no longer working or no longer provides readers access to the content you intend to cite, follow the guidance for works with no source.
- Other alphanumeric identifiers such as the International Standard Book Number (ISBN) and the International Standard Serial Number (ISSN) are not included in APA Style references.
Format of DOIs and URLs
Follow these guidelines to format DOIs and URLs:
- Present both DOIs and URLs as hyperlinks (i.e., beginning with “http:” or “https:”).
- Because a hyperlink leads readers directly to the content, it is not necessary to include the words “Retrieved from” or “Accessed from” before a DOI or URL.
- It is acceptable to use either the default display settings for hyperlinks in your word-processing program (e.g., usually blue font, underlined) or plain text that is not underlined.
- Leave links live if the work is to be published or read online.
- Follow the current recommendations of the International DOI Foundation to format DOIs in the reference list, which as of this publication is as follows:
- The string “https://doi.org/” is a way of presenting a DOI as a link, and “xxxxx” refers to the DOI number.
- 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. For example, use https://doi.org/10.1037/a0040251 in your reference even though that article, published in 2016, presented the number in an older format.
- Copy and paste the DOI or URL from your web browser directly into your reference list to avoid transcription errors. Do not change the capitalization or punctuation of the DOI or URL. Do not add line breaks manually to the hyperlink; it is acceptable if your word-processing program automatically adds a break or moves the hyperlink to its own line.
- Do not add a period after the DOI or URL because this may interfere with link functionality.
DOI and URL shorteners
When a DOI or URL is long or complex, you may use shortDOIs or shortened URLs if desired.
- Use the shortDOI service provided by the International DOI Foundation to create shortDOIs. A work can have only one DOI and only one shortDOI; the shortDOI service will either produce a new shortDOI for a work that has never had one or retrieve an existing shortDOI.
- Some websites provide their own branded shortened URLs, and independent URL shortening services are available as well. Any shortened URL is acceptable in a reference as long as you check the link to ensure that it takes you to the correct location.