DOI, ISSN, ISBN and ORCID: What Each Identifier Tells You
Four identifiers appear on almost every piece of research you read. Each answers a different question — and none of them, on its own, tells you whether the work is good.
| Identifier | Identifies | Looks like | Check it at |
|---|---|---|---|
| DOI | One specific item (article, chapter, dataset) | 10.xxxx/… | doi.org |
| ISSN | A serial publication (journal, magazine, series) | 1234-5679 | ISSN Portal |
| ISBN | One edition and format of a book | 13 digits | National ISBN agency / library catalogues |
| ORCID iD | A person (researcher) | 0000-0000-0000-0000 | orcid.org |
What is a DOI?
A Digital Object Identifier is a persistent identifier for a single piece of content. Every DOI begins with 10., followed by a prefix assigned to the registrant, a slash, and a suffix. Its value is persistence: when content moves, the registrant updates where the DOI points, so a citation with a DOI keeps working after a website changes. The DOI system is governed by the DOI Foundation; research articles are usually registered through Crossref, and datasets often through DataCite.
What it does not prove: a DOI shows that an item was registered, not that it was peer reviewed. Preprints, reports and datasets can all have DOIs.
How to check: paste it after https://doi.org/. If the resolver cannot find it, the number was never registered — sometimes a sign of a printed “DOI” that isn’t one.
What is an ISSN?
An International Standard Serial Number is an eight-digit code (the last character is a check digit, which can be X) that identifies a serial publication as a whole. The print and online versions of a journal usually have different ISSNs; a “linking ISSN” (ISSN-L) groups them. ISSNs are assigned through the ISSN network coordinated by the ISSN International Centre.
What it does not prove: an ISSN is an identification number, not a quality mark or an indexing credential. Any legitimate serial can obtain one.
How to check: search it at the ISSN Portal and compare the record’s title, publisher and URL with the journal’s website. A mismatch is a serious warning sign — see how to evaluate a journal.
What is an ISBN?
An International Standard Book Number identifies one edition in one format of a book: the paperback, hardback and e-book of the same title normally have different ISBNs. Since 2007 ISBNs have 13 digits.
What it does not prove: that the book was peer reviewed or published by an academic press.
What is an ORCID iD?
ORCID gives researchers a free, persistent 16-character identifier, so that their work can be linked to them regardless of name variations, spelling or changes of institution.
Why it helps you as a reader: an author’s ORCID record can show their affiliations and publication list — useful when you are verifying an editorial board or trying to contact an author about a paper you cannot find (see finding papers from defunct journals).
In one line: DOI = which item, ISSN = which journal, ISBN = which book edition, ORCID = which person. Quality is a separate question.