What Is a DOI and How Do You Find One?
Updated November 6, 2026
A DOI, or Digital Object Identifier, is a permanent ID for a journal article, book chapter, dataset, or other work. You can usually find it on the first page of an article or on the journal’s page for it. Put https://doi.org/ in front of it, and the link takes you to that work.
Here’s a real one: 10.1038/171737a0. As a link, it’s https://doi.org/10.1038/171737a0. It leads to Watson and Crick’s 1953 paper in Nature on the structure of DNA.
Why DOIs exist
Web addresses break. Sites get redesigned, and journals move to new publishers. A DOI fixes this by giving each work an ID that doesn’t change. When the work moves, the DOI stays the same, and the link gets pointed to the new home.
That’s why citation styles like DOIs better than regular links. Your reader can still find the source years later.
What the parts of a DOI mean
Every DOI has a prefix and a suffix, split by a slash.
| Part | In 10.1038/171737a0 |
What it means |
|---|---|---|
| Prefix | 10.1038 |
Always starts with 10. The rest points to the group that registered the DOI. |
| Suffix | 171737a0 |
A string of characters that group chooses |
Suffixes often look random, and that’s normal. Crossref says they aren’t case sensitive, so capital letters don’t change the DOI.
Groups called registration agencies assign DOIs. Crossref is a not-for-profit agency that works with scholarly publishers. DataCite is another agency, and you’ll often see it with datasets.
How to find a DOI
Work down this list until you find one.
- Look at the first page of the PDF. It’s often near the title, or in the header or footer.
- Check the article’s page on the journal’s website.
- Check the record in your library database. EBSCO and ProQuest records often list it.
- Search the title on Crossref. Each match shows its DOI.
- Go from Google Scholar to the publisher’s page. Scholar results usually don’t show a DOI, but the publisher’s page often does.
Have a full citation instead of a title? Try the free citation checker from Sourcefox.
Not every source has a DOI
Many web pages, news stories, and books don’t have one. Older works vary, too. The 1953 paper above has a DOI, but plenty of old articles don’t.
A missing DOI doesn’t mean a source is bad or fake. Use the link or permalink your citation style asks for.
How to tell a DOI from other numbers
An article page can show several ID numbers. Only one of them is the DOI.
| ID | What it looks like | What it points to |
|---|---|---|
| DOI | Starts with 10. and has a slash |
One article or other work |
| ISSN | Eight digits with a hyphen, like 0022-3514 |
A whole journal |
| ISBN | 10 or 13 digits | A book |
| PMID | A plain number | A paper in PubMed |
If a number doesn’t start with 10., it isn’t a DOI.
How to open a DOI
Add the DOI to the end of https://doi.org/ and paste the whole thing into your browser. If you land on an abstract with a paywall, the DOI still did its job. Go through your college library to get the full text.
If you see a “DOI not found” page, doi.org lists three likely reasons:
- The DOI in your source is wrong.
- It was copied wrong, with missing characters or stray punctuation.
- It hasn’t been activated yet.
Copying from a PDF can cause the second problem. It can add a space or a line break, and a period at the end of a citation can sneak in. Remove those and try again.
If it still fails, search the title. Our guide on how to check if a citation is real walks you through each step.
How to write a DOI in a citation
APA 7, MLA 9, and Chicago 17 all use the full link form.
| Style | How it ends the citation | Period after it? |
|---|---|---|
| APA 7 | https://doi.org/10.1037/0022-3514.77.6.1121 |
No |
| MLA 9 | https://doi.org/10.1037/0022-3514.77.6.1121. |
Yes |
| Chicago 17 | https://doi.org/10.1037/0022-3514.77.6.1121. |
Yes |
That sample DOI belongs to a 1999 paper by Justin Kruger and David Dunning in the Journal of Personality and Social Psychology.
In APA, skip the period because it can break the link. In MLA 9, keep https://doi.org/ on every DOI, even though you can drop https:// from regular web addresses.
Older papers and websites may print a DOI in an older form. APA’s advice is to update these in your reference list, and the same fix works for MLA and Chicago.
| Form you might see | Write it as |
|---|---|
doi:10.1037/0022-3514.77.6.1121 |
https://doi.org/10.1037/0022-3514.77.6.1121 |
http://dx.doi.org/10.1037/0022-3514.77.6.1121 |
https://doi.org/10.1037/0022-3514.77.6.1121 |
For full citations, see our MLA 9 works cited examples and Chicago style examples.
What a DOI doesn’t tell you
A DOI shows that a work was registered. It doesn’t show that the work is good.
Keep these limits in mind:
- A DOI doesn’t mean a paper was peer reviewed.
- A retracted paper usually keeps its DOI, so a working link doesn’t mean the paper still stands.
- A fake citation can borrow a real DOI from a different paper.
So when a DOI opens, read the page. Make sure the title and authors match your citation.
Common questions
Is a DOI the same as a URL?
Not quite. A URL is a web address that can change. A DOI is a permanent ID that works as a link once you add https://doi.org/.
Is it free to use a DOI?
Yes, opening a DOI link is free. doi.org says existing DOI names “are, and will always be, free to resolve.” The article it leads to may still be behind a paywall.
Do books have DOIs?
Some do, especially from academic publishers, and single chapters can have their own. Most books use an ISBN, which is a different kind of number.