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Short answer: a DOI link is a DOI written as a full web address, https://doi.org/ followed by the DOI itself, for example https://doi.org/10.3390/rel11010015. The DOI inside it always has two parts, a prefix that starts with 10. and a suffix, joined by a forward slash. This guide is for authors, editors and librarians who need to write, check or format a DOI correctly.
What a DOI link is
A Digital Object Identifier (see DOI) names a scholarly object such as an article or dataset. The identifier itself is just the string 10.xxxx/xxxxx. A DOI link adds the https://doi.org/ resolver address in front, so a reader can click it and be taken to the object’s current landing page. DataCite’s documentation states that the doi.org proxy is not part of the DOI specification itself; it is how a DOI is made actionable on the web (DataCite Support, “DOI Basics”, read 2026-11-08).
Crossref’s display guidelines say DOIs should always be displayed as a full URL link in the form https://doi.org/10.xxxx/xxxxx (Crossref, “DOI display guidelines”, read 2026-11-08). The difference between the bare identifier and the link is covered further in DOI vs URL.
DOI structure: prefix and suffix
Per DataCite, a DOI is a unique number made up of a prefix and a suffix separated by a forward slash. Split a DOI at the first slash:
| Part | Example (10.5281/zenodo.31780) | What it is |
|---|---|---|
| Prefix | 10.5281 |
Always starts with 10. and continues with a number. The number has no inherent meaning. |
| Separator | / |
The forward slash between prefix and suffix. |
| Suffix | zenodo.31780 |
Can be almost any string of characters and symbols, chosen by whoever registers the DOI. |
The DOI Handbook gives 10.1000/182 as its canonical example of the same pattern. See also the dictionary entries for DOI prefix and DOI suffix.
DOI prefix
DataCite states that the prefix number has no inherent meaning, so do not infer a publisher, journal, field or date from it. Use the agency lookup below if you need to know who registered it.
DOI suffix
DataCite recommends random-looking suffixes and advises avoiding reserved characters, trailing slashes, human-readable text and version labels in them. Many suffixes you will meet are nonetheless readable, such as rel11010015 or zenodo.31780, because registrants are free to choose. Treat the suffix as an opaque string and copy it exactly.
DOI URL format
The recommended pattern is https://doi.org/ + prefix + / + suffix. The rules below come from Crossref’s display guidelines and DataCite’s DOI Basics (both read 2026-11-08).
| Form | Status |
|---|---|
https://doi.org/10.3390/rel11010015 |
Recommended display form (full URL, HTTPS). |
doi:10.3390/rel11010015 or DOI: 10.3390/rel11010015 |
Not the recommended display form; Crossref says a DOI link should not be preceded by doi: or DOI:. |
http://dx.doi.org/... |
Crossref says not to use dx in the domain, and recommends HTTPS rather than HTTP. |
For a compact link, see shortDOI. For turning a DOI into a reference-manager entry, see getting clean BibTeX from a DOI.
DOI examples
| DOI link | Prefix | Suffix | Registration agency (doi.org lookup, 2026-11-08) |
|---|---|---|---|
https://doi.org/10.3390/rel11010015 |
10.3390 | rel11010015 | Crossref |
https://doi.org/10.5281/zenodo.31780 |
10.5281 | zenodo.31780 | DataCite |
https://doi.org/10.1000/182 |
10.1000 | 182 | DOI Handbook example |
The first example is the one Crossref uses in its display guidelines; the second is the one DataCite uses to show that suffix case does not matter.
DOI prefix lookup: who registered it
A prefix does not tell you the publisher, but the DOI system can tell you which registration agency issued it. The doi.org service answers a prefix query at https://doi.org/doiRA/ followed by the prefix. On 2026-11-08 https://doi.org/doiRA/10.5281 returned DataCite and https://doi.org/doiRA/10.3390 returned Crossref. The two largest agencies each have their own metadata tools: Crossref DOIs and DataCite DOIs. For why several agencies exist, see DOI registration agency.
Case and characters
DataCite states that DOI suffixes are not case sensitive: 10.5281/ZENODO.31780 and 10.5281/zenodo.31780 are the same DOI. Crossref’s display guidelines give no case rule, so copy the form the registrant displays. The DOI Handbook allows a suffix of any printable Unicode characters with no length limit, which is why copying the whole string, including punctuation, matters. Paste the link into a browser to confirm it resolves.
Common mistakes
- Prefixing with “doi:” or “DOI:” in front of a link. Crossref’s guidance is to show the full URL instead.
- Using the legacy dx.doi.org domain or plain http. Use
https://doi.org/. - Trying to read meaning into the prefix. It is not a journal code.
- Dropping or retyping punctuation in the suffix. Copy, do not retype; suffixes can contain dots, hyphens and other symbols.
- Confusing a DOI with a PubMed ID. They are different identifiers; see PMID vs DOI.
FAQ
What is a DOI link?
A DOI shown as a full URL beginning https://doi.org/, so it can be clicked and resolved to the object’s current location.
What is the DOI format?
A prefix beginning 10. and a number, a forward slash, then a suffix, as in 10.1000/182.
What does a DOI prefix mean?
A number that starts with 10.; DataCite states it has no inherent meaning.
Is a DOI case sensitive?
Not in the suffix, according to DataCite. Display it as the registrant gives it.
How do I find which agency registered a DOI?
Query https://doi.org/doiRA/ plus the prefix; the response names the registration agency.
Sources
- Crossref, “DOI display guidelines”, https://www.crossref.org/display-guidelines (read 2026-11-08).
- DataCite Support, “DOI Basics”, https://support.datacite.org/docs/doi-basics (read 2026-11-08).
- International DOI Foundation, DOI Handbook, https://www.doi.org/doi-handbook (suffix and example facts checked 2026-07-11).
- doi.org registration-agency lookup, https://doi.org/doiRA/ (queried 2026-11-08).
