What Is a DOI? Digital Object Identifier Explained (With Examples)
A DOI (Digital Object Identifier) is a permanent link to a digital publication. Learn what DOIs are, how to find them, and how to use them in APA, MLA, and Chicago citations.
A DOI (Digital Object Identifier) is a permanent, unique identifier assigned to digital content like journal articles, books, and datasets. It looks like 10.1038/s41586-024-07421-0 and resolves to the content even if the URL changes. Always include DOIs in citations when available. Find a DOI on the article page, in the database record, or via CrossRef.org.
TL;DR: A DOI is a permanent, unique ID for digital publications. Format: 10.XXXX/XXXXX. Always include it in citations when available. Find it on the article page or at CrossRef.org.
If you've ever clicked a broken link to a journal article, you understand why DOIs exist. Publishers change URLs, redesign websites, and move content between servers. A DOI (Digital Object Identifier) is a permanent link that always works, no matter what happens to the publisher's website.
A DOI is a unique, permanent identifier assigned to a specific piece of digital content — usually a journal article, book, book chapter, dataset, or conference paper. It's managed by the International DOI Foundation and assigned by registration agencies like CrossRef.
A DOI has two parts: Prefix (10.XXXX): Identifies the publisher. 10.1038 = Nature, 10.1126 = Science, 10.1016 = Elsevier Suffix: Unique identifier for the specific work
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Frequently Asked Questions
- What is a DOI number?
- A DOI (Digital Object Identifier) is a unique, permanent identifier for digital content — primarily journal articles, books, book chapters, datasets, and conference papers. It follows the format 10.XXXX/XXXXX (prefix/suffix). Unlike URLs, a DOI never changes even if the content moves to a different server. DOIs are assigned by registration agencies like CrossRef.
- What does a DOI look like?
- A DOI has two parts separated by a slash: a prefix (starts with 10.) and a suffix. Examples: 10.1038/s41586-024-07421-0 (Nature), 10.1126/science.abc1234 (Science), 10.1016/j.cell.2024.01.001 (Cell). When formatted as a URL: https://doi.org/10.1038/s41586-024-07421-0.
- How do I find the DOI of an article?
- Three ways: (1) Look on the article page — most journals display the DOI near the title, abstract, or citation info, (2) Search on CrossRef.org — enter the title, author, or metadata, (3) Check your database — PubMed, Google Scholar, and Scopus all show DOIs. If an article doesn't have a DOI, it may be older (pre-2000) or from a journal that doesn't register DOIs.
- Do all articles have a DOI?
- No. Most articles published after 2000 in major journals have DOIs. Older articles, articles from smaller journals, preprints (unless on Zenodo or similar), and some open-access publications may not. If no DOI exists, use the URL in your citation instead.
- How do I use a DOI in a citation?
- APA 7: Format as https://doi.org/10.XXXX/XXXXX at the end of the reference. MLA 9: Same URL format. Chicago: Same URL format. Always use the https://doi.org/ prefix. Example: Smith, J. (2024). Title. Journal, 1(2), 1-10. https://doi.org/10.1038/s41586-024-07421-0
- What is the difference between a DOI and a URL?
- A DOI is a permanent identifier that always resolves to the content. A URL is a web address that can break if the publisher moves the content. DOIs redirect through doi.org to the current URL. Think of a DOI as a permanent forwarding address, and a URL as a physical address that might change.