An International Standard Serial Number identifies a continuing publication as a whole — the journal itself, not any single article within it. A DOI does the opposite: it identifies one specific article, permanently, down to that exact version of record. Confusing the two is an easy mistake, and it shows up more often than expected in reference lists and library catalog entries.

Print and online versions of the same journal typically carry separate ISSNs, since they are technically distinct serial formats even when the content is identical. This is why a journal's about page usually lists two numbers rather than one, and why citing the wrong one is a minor but real error worth avoiding.

Neither identifier says anything about editorial quality on its own. An ISSN is a cataloguing number, assigned to help libraries and databases track continuing publications consistently — it is not a peer-review credential, and registering one is a formality, not an endorsement.