The ISSN or International Standard Serial Number identifies a serial publication, such as a newspaper, magazine, or academic journal, or blog; it is the periodical counterpart of the ISBN for a book. It does not identify a particular issue or a particular article in an issue. DOIs identify particular articles (but are mostly only available for academic journal articles). On Wikipedia, an ISSN is an optional part of a citation to a particular article (adding it never hurts, but it is not strictly necessary when a direct URL or DOI is provided to the full text of the article).

An ISSN is particularly helpful in the following circumstances (especially when the ISSN is linked, using template or parameter detailed below):

• In a citation to a periodical that is relatively unknown, as the ISSN can help in verifying the existence and reliability of the journal and procuring a copy of one of its issues to verify the content.
• In relevant non-citation contexts on Wikipedia, such as in the lead section or infobox of an article about a publication itself.

The {{ISSN}} template can be used to insert and format an ISSN in an article. If a standardized citation template is being used, the |issn= parameter serves the same function, linking the ISSN to the WorldCat database, which provides publication details and aids in locating physical copies of publications.