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URLs vs. DOIs

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While citation styles can vary greatly in their particulars, most major styles (including APA, MLA, and Chicago) require writers to include either a URL or a DOI in citations for digital content whenever possible. You do not normally need to include both.

This resource explains the difference between URLs and DOIs and briefly describes how to incorporate either form of information into your citations.

What are DOIs?

When sources are published electronically, they are assigned DOIs—a unique series of letters and numbers set by the International DOI Foundation. The IDF, founded in 1998, handles creator requests for DOIs and standardizes each DOI they assign. Every DOI begins with the number 10, and can generally be found on the first page of the digital article. DOIs also associate their publications with metadata, or relevant information related to each source (such as author, location, and date information). Because DOIs are assigned when a source is published electronically, some older sources will not have DOIs. If you are citing a print source and want to know if it has been assigned a DOI, use CrossRef.org’s DOI lookup on the website’s home page.

DOIs differ from URLs in that they are static. In other words, once they are assigned, they will not change, which makes it very easy to locate at any future time (even after it has been moved). Here is an example DOI for Ryan LaMothe’s article “Pebbles in the Shoe: Acts of Compassion as Subversion in a Market Society,” published in the journal Pastoral Psychology:

DOI: 10.1007/s11089-018-0833-1

This image shows the title page of the Ryan LaMothe article “Pebbles in the Shoe: Acts of Compassion as Subversion in a Market Society.”

The title page of a scholarly article hosted online. Note the DOI at the top of the page.

When should I use a URL?

In the event that a source does not have a DOI assigned, or if the citation style you are using specifically calls for URLs over DOIs, cite the source’s URL. This is its ordinary web address, which typically appears in the navigation bar at the top of your web browser.

Here is an example of a URL for the Purdue OWL homepage:

https://owl.purdue.edu/owl/purdue_owl.html

This image shows a screenshot of a Safari browser window cropped so that it is centered on the Purdue OWL homepage URL, visible in the address field.

A screenshot of a web browser's navigation bar. Note that the Purdue OWL homepage URL is visible in the address field.

URLs can change if the website is edited or updated, or the source is moved. Because of this, many online databases (such as library websites and scholarly article repositories) assign sources with stable URLs (sometimes called “permalinks”) unique to the database’s own website for this purpose. Like DOIs, these will not change and will link directly to the source on that specific webpage.

Note that some citation styles provide specific directions for how to format source URLs. For example, MLA only requires the www. portion of the URL, so leave off the https://.

Quick Guide

The following chart breaks down the use of DOIs and URLs in four major citation styles and provides links to OWL pages that describe DOI and/or URL formatting rules for citations in those styles. Note that some of the styles have very similar guidelines.

For more in-depth information on formatting DOIs and URLs in your citations, be sure to consult the style guide for whatever style you are using, as each has different ordering and formatting preferences.

Style DOI/URL Guidelines OWL Resource
MLA
  • Provide DOIs over URLs whenever possible.
  • If no DOI is available, use the source’s URL in the citation.
  • In MLA style, stable URLs are preferrable to normal URLs. Use them if they are available.
  • Place the DOI or URL before the access date, which comes at the end of the citation. The rest of the citation should be formatted as normal for an equivalent non-digital source.
  • Access dates are optional when using DOIs.
  • A DOI should be preceded by a "doi:" label (note the lowercase).
  • If using a URL, do not include the "https://" or "http://" portion of the string. This means that most addresses will begin with "www."

Generic Journal Citation:

Author. "Title." Title of journal, Other contributors (translators or editors), Number (vol. and/or issue no.), publication year, www.someaddress.com/full/url/ or doi:0000000/00000000000. Accessed dd Mmm. yyyy.

 Works Cited: Electronic Sources
APA
  • Provide DOIs over URLs whenever possible.
  • If no DOI is available, use the source’s URL in the citation.
  • Place the DOI or URL at the end of the citation, formatting the rest of the citation as normal for an equivalent non-digital source.
  • A DOI should be preceded by a "doi:" label (note the lowercase).
  • The APA allows for the use of either the modern alphanumeric string format ("doi:0000000/000000000000") or the older doi.org format ("https://doi.org/10.0000/0000"). Use whichever is provided by the source.
  • If using a URL, include the phrase "Retrieved from..." before the URL.

Generic Journal Citation:

Author, A. A., & Author, B. B. (Date of publication). Title of article. Title of Journal, volume number(issue number if available), page range. doi:0000000/000000000000 or https://doi.org/10.0000/0000 or Retrieved from https://www.someaddress.com/full/url/.

 Reference List: Electronic Sources
Chicago
  • Provide DOIs over URLs whenever possible.
  • If no DOI is available, use the source’s URL in the citation.
  • Place the DOI or URL at the end of the citation, formatting the rest of the citation as normal for an equivalent non-digital source.
  • A DOI should be preceded by a "doi:" label (note the lowercase).
  • Access dates are not required for formally published electronic sources (like journal articles). They can be useful for informally published electronic sources. They may also be required for some disciplines for all electronic sources (formal or informal). Access dates should be located immediately prior to the DOI or URL.

Generic Journal Citation:

Lastname, First/middle initials. “Title of Article.” Journal Title volume number, issue no. (Year): page range. https://www.someaddress.com/full/url/ or doi:0000000/000000000000

 

 Web Sources
AMA
  • Provide DOIs over URLs whenever possible.
  • If no DOI is available, use the source’s URL in the citation.
  • If using a DOI, omit the URL, access date, and publication date from Reference List entry. Instead, add the DOI preceded by a "doi:" label (note the lowercase). 
  • If using a URL, include the access date and publication date after the URL.

Generic Journal Citation:

Author(s). Title. Journal Name. Year;vol(issue no.):page range. https://www.someaddress.com/full/url/ or doi:10.0000000/000000000000

 Electronic Sources