The ISSN (International Standard Serial Number) provides important information about a journal, because it is an unambiguous identifier which prevents readers as well as potential authors from confusing journals with similar titles. When verifying this criterion, first the ISSN of the journal must be found and then checked on the ISSN Portal (https://portal.issn.org/). One should verify whether the journal can be retrieved on this portal according to its ISSN and whether the information recorded in the ISSN corresponds to that included on the website of the journal (e.g. information about the publisher, the frequency of the journal’s publication, etc.).
When trying to find the ISSN, you need to inspect the website of the journal very thoroughly, because it may not be easy to find at first sight.
You can see this in the following examples. While the journal World Psychiatry provides its ISSN right in the heading of its website…
… the journal Nature placed this information just above the footer of its website and only in small print.
Sometimes finding the ISSN may be complicated. For example, the journal Cell does not provide its ISSN either on itshomepage, or on any subpages in the About section, where the reader would commonly expect such information, but instead only on the page with information about subscriptions.