What Is a DOI and How Do You Cite It?
A DOI (Digital Object Identifier) is a permanent alphanumeric string assigned to a specific academic article, dataset, or publication so it can be reliably located on the internet regardless of where it is hosted. When you include a DOI in a citation, you are giving readers a stable path to the source, one that stays valid even if the journal moves to a new publisher or the website reorganizes its URL structure. If you want the fastest way to format DOI-based citations, use the OnSumo citation generator. Paste the article URL or DOI link and the tool fills in the citation fields for APA, MLA, and Chicago.
What is a DOI number?
A DOI (Digital Object Identifier) is a permanent alphanumeric string assigned to a specific academic article, dataset, or publication so it can be reliably located on the internet regardless of where it is hosted. The DOI system is maintained by the International DOI Foundation through a registration agency called doi.org. When a publisher assigns a DOI to an article, that string is registered in a central database. Anyone can resolve a DOI to its current location by visiting https://doi.org/ followed by the DOI string. A typical DOI looks like this: 10.1001/jama.2023.12345 - The prefix (before the slash) identifies the publisher or registrant. 10.1001 is the prefix for JAMA. - The suffix (after the slash) is a unique identifier assigned by the publisher for that specific article. DOIs are assigned at the article level, not the journal level. Two articles in the same journal issue have different DOIs.
Where do you find the DOI for an article?
DOIs appear in several places, depending on how you accessed the article: - On the article's abstract or landing page. Most journal websites display the DOI at the top of the abstract page, often labeled "DOI:" or formatted as a hyperlink starting with https://doi.org/. - In the PDF. Check the first page, usually in the header or footer near the journal name and issue information. - In the article's citation metadata. Databases like PubMed, JSTOR, and Google Scholar display the DOI alongside the citation data when you click through to an article record. - Via doi.org. If you have partial citation information but no DOI, the CrossRef metadata search at doi.org lets you look up DOIs by article title and author. If the DOI does not appear in any of these places, the article may predate the DOI system (widely adopted in the early 2000s) or may not have been assigned one by the publisher.
How do you format a DOI in an APA citation?
In APA 7th edition, a DOI is formatted as a hyperlink: https://doi.org/ followed by the DOI string, placed at the end of the reference entry. Format: Last, F. M., & Last, F. M. (Year). Title of article in sentence case. Name of Journal, volume(issue), page-page. https://doi.org/10.xxxx/xxxxx Example: Nguyen, T. L., & Patel, S. R. (2022). Sleep fragmentation and cardiovascular risk in adults over 50. Journal of Sleep Research, 31(4), e13567. https://doi.org/10.1111/jsr.13567 Key APA rules for DOIs: - If a journal article has a DOI, APA style requires you to include it even when a URL is also available. The DOI takes priority. - Format the DOI as a live hyperlink starting with https://doi.org/. Do not use the old doi: prefix format (that was the APA 6th edition convention). - No period follows the DOI at the end of the citation. - If the article has no DOI but is available online, include the URL instead. Source: American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). APA.
How do you format a DOI in an MLA citation?
To format a DOI in an MLA citation, place it at the end of the entry as the location, using the full https://doi.org/ link. Format: Last, First. "Article Title." Journal Name, vol. 31, no. 4, Year, pp. 45-67, https://doi.org/10.xxxx/xxxxx. Example: Nguyen, Tran L., and Sanjiv R. Patel. "Sleep Fragmentation and Cardiovascular Risk in Adults Over 50." Journal of Sleep Research, vol. 31, no. 4, 2022, https://doi.org/10.1111/jsr.13567. MLA notes: - When a DOI is available, it is preferred over a URL because it is more stable. - Format it as https://doi.org/ followed by the string, the same hyperlink format APA uses. - A period follows the DOI at the end of an MLA citation (unlike APA, which uses no trailing period after the DOI).
What do you do when a source has no DOI?
If a source has no DOI, use the URL, database name, or print publication details that your citation style calls for instead. When there is no DOI: - APA: Include the URL where you found the article, or no URL at all for print sources. If the article came from a library database and has no publicly accessible URL, APA does not require a URL because the citation information alone is sufficient. - MLA: Include the URL or the database name (e.g., JSTOR, EBSCOhost) as the location. - Chicago: Include a URL or database access information, plus an access date if the content may change. For print-only sources with no digital version, neither a DOI nor a URL is needed. The publisher information in the citation is sufficient for a reader to locate the source through a library catalog.
Can a citation generator find and format the DOI automatically?
Yes. When you paste an article URL into a citation generator, the tool queries the metadata for that page, which typically includes the DOI. The generator then formats it in the correct style. The OnSumo citation generator handles DOI detection and formatting for APA, MLA, and Chicago. For journal articles from major publishers, it identifies the DOI from the URL and includes it in the output automatically, so you do not need to locate and copy the DOI separately. For articles accessed through a DOI link directly (e.g., https://doi.org/10.1001/jama.2023.12345), paste that URL into the citation generator and it resolves the metadata and formats the full citation. If the DOI is not detected automatically, which happens with some older articles or less common publishers, the generator flags the missing field so you can add it manually. If you need the full website citation pattern around that DOI, read How to Cite a Website. If you are building the full references page after collecting article citations, read How to Write a Bibliography. This guide was written for academic research workflows and reviewed against DOI Foundation documentation plus the major citation manuals used in college writing. DOI definitions and formatting rules were checked against doi.org, the APA 7th edition manual, and the MLA 9th edition handbook. FAQ
Is a DOI the same thing as a URL?
No. A DOI is a permanent identifier, while a URL is a web address that can change if the content moves to a new page or publisher site.
Do all journal articles have a DOI?
No. Many recent journal articles have DOIs, but older articles, print-only sources, and some smaller publications may not have one assigned.