If you have ever formatted a reference list, you have seen DOIs. But what are they, and why do citation styles insist you include them?
What is a DOI?
A DOI (Digital Object Identifier) is a permanent, unique identifier assigned to a digital document — usually an academic paper, book chapter, or dataset.
It looks like this: 10.1080/13676261.2023.1234567
Or as a URL: https://doi.org/10.1080/13676261.2023.1234567
Why DOIs matter
Permanent links
Unlike regular URLs, DOIs never break. A journal might move to a new website, but the DOI will always resolve to the correct paper. This makes your reference list future-proof.
Unique identification
Every DOI is unique. Two papers cannot share the same DOI. This eliminates confusion when papers have similar titles or authors.
Required by citation styles
APA 7, Harvard, IEEE, and most other citation styles require DOIs when available. Omitting a DOI is a formatting error that can cost marks.
Verification
A DOI confirms a paper is a legitimate, registered publication. If a paper has a DOI, it exists.
How to find a DOI
- On the paper itself — usually on the first page or in the header/footer
- In the database record — Scholise, Google Scholar, and PubMed all show DOIs
- CrossRef lookup — paste the title at crossref.org/SimpleTextQuery to find the DOI
- Journal website — usually in the article metadata
What if a paper has no DOI?
Some papers — especially older ones or those from smaller journals — do not have DOIs. In that case:
- APA 7: Include the journal homepage URL instead
- Harvard: Include the database URL or journal URL
- IEEE: No URL needed if journal name and volume are complete
How to format a DOI
APA 7: https://doi.org/10.1080/xxxxx (as a hyperlink, no "Retrieved from")
Harvard: doi:10.1080/xxxxx (some variants use the full URL)
IEEE: doi: 10.1080/xxxxx
Important: Never put a full stop after a DOI — it can break the link.
Common DOI mistakes
- Adding a full stop at the end
- Using "Retrieved from" before the DOI (outdated in APA 7)
- Not including the DOI when one exists
- Confusing DOI with URL (DOIs start with 10.xxxx)
- Using a dx.doi.org link instead of doi.org (both work, but doi.org is current)
Scholise automatically includes DOIs in your exported reference lists. Try Scholise free →